\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename guix-cookbook.info @documentencoding UTF-8 @settitle GNU Guix Cookbook @c %**end of header @c Onion service for ci.guix.gnu.org. @set SUBSTITUTE-TOR-URL https://4zwzi66wwdaalbhgnix55ea3ab4pvvw66ll2ow53kjub6se4q2bclcyd.onion @copying Copyright @copyright{} 2019, 2022 Ricardo Wurmus@* Copyright @copyright{} 2019 Efraim Flashner@* Copyright @copyright{} 2019 Pierre Neidhardt@* Copyright @copyright{} 2020 Oleg Pykhalov@* Copyright @copyright{} 2020 Matthew Brooks@* Copyright @copyright{} 2020 Marcin Karpezo@* Copyright @copyright{} 2020 Brice Waegeneire@* Copyright @copyright{} 2020 André Batista@* Copyright @copyright{} 2020 Christine Lemmer-Webber@* Copyright @copyright{} 2021 Joshua Branson@* Copyright @copyright{} 2022, 2023 Maxim Cournoyer@* Copyright @copyright{} 2023 Ludovic Courtès@* Copyright @copyright{} 2023 Thomas Ieong Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1
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path: root/nix/libutil/affinity.cc
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#include "types.hh"
#include "util.hh"
#include "affinity.hh"

#if HAVE_SCHED_H
#include <sched.h>
#endif

namespace nix {


#if HAVE_SCHED_SETAFFINITY
static bool didSaveAffinity = false;
static cpu_set_t savedAffinity;
#endif


void setAffinityTo(int cpu)
{
#if HAVE_SCHED_SETAFFINITY
    if (sched_getaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) return;
    didSaveAffinity = true;
    printMsg(lvlDebug, format("locking this thread to CPU %1%") % cpu);
    cpu_set_t newAffinity;
    CPU_ZERO(&newAffinity);
    CPU_SET(cpu, &newAffinity);
    if (sched_setaffinity(0, sizeof(cpu_set_t), &newAffinity) == -1)
        printMsg(lvlError, format("failed to lock thread to CPU %1%") % cpu);
#endif
}


int lockToCurrentCPU()
{
#if HAVE_SCHED_SETAFFINITY
    int cpu = sched_getcpu();
    if (cpu != -1) setAffinityTo(cpu);
    return cpu;
#else
    return -1;
#endif
}


void restoreAffinity()
{
#if HAVE_SCHED_SETAFFINITY
    if (!didSaveAffinity) return;
    if (sched_setaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1)
        printMsg(lvlError, "failed to restore affinity %1%");
#endif
}


}
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Bonus: Manifest. * Wrapping Up:: Recap. Environment management * Guix environment via direnv:: Setup Guix environment with direnv Installing Guix on a Cluster * Setting Up a Head Node:: The node that runs the daemon. * Setting Up Compute Nodes:: Client nodes. * Cluster Network Access:: Dealing with network access restrictions. * Cluster Disk Usage:: Disk usage considerations. * Cluster Security Considerations:: Keeping the cluster secure. @end detailmenu @end menu @c ********************************************************************* @node Scheme tutorials @chapter Scheme tutorials GNU@tie{}Guix is written in the general purpose programming language Scheme, and many of its features can be accessed and manipulated programmatically. You can use Scheme to generate package definitions, to modify them, to build them, to deploy whole operating systems, etc. Knowing the basics of how to program in Scheme will unlock many of the advanced features Guix provides --- and you don't even need to be an experienced programmer to use them! Let's get started! @menu * A Scheme Crash Course:: @end menu @node A Scheme Crash Course @section A Scheme Crash Course @cindex Scheme, crash course Guix uses the Guile implementation of Scheme. To start playing with the language, install it with @code{guix install guile} and start a @dfn{REPL}---short for @uref{https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop, @dfn{read-eval-print loop}}---by running @code{guile} from the command line. Alternatively you can also run @code{guix shell guile -- guile} if you'd rather not have Guile installed in your user profile. In the following examples, lines show what you would type at the REPL; lines starting with ``@result{}'' show evaluation results, while lines starting with ``@print{}'' show things that get printed. @xref{Using Guile Interactively,,, guile, GNU Guile Reference Manual}, for more details on the REPL. @itemize @item Scheme syntax boils down to a tree of expressions (or @emph{s-expression} in Lisp lingo). An expression can be a literal such as numbers and strings, or a compound which is a parenthesized list of compounds and literals. @code{#true} and @code{#false} (abbreviated @code{#t} and @code{#f}) stand for the Booleans ``true'' and ``false'', respectively. Examples of valid expressions: @lisp "Hello World!" @result{} "Hello World!" 17 @result{} 17 (display (string-append "Hello " "Guix" "\n")) @print{} Hello Guix! @result{} # @end lisp @item This last example is a function call nested in another function call. When a parenthesized expression is evaluated, the first term is the function and the rest are the arguments passed to the function. Every function returns the last evaluated expression as its return value. @item Anonymous functions---@dfn{procedures} in Scheme parlance---are declared with the @code{lambda} term: @lisp (lambda (x) (* x x)) @result{} #:24:0 (x)> @end lisp The above procedure returns the square of its argument. Since everything is an expression, the @code{lambda} expression returns an anonymous procedure, which can in turn be applied to an argument: @lisp ((lambda (x) (* x x)) 3) @result{} 9 @end lisp Procedures are regular values just like numbers, strings, Booleans, and so on. @item Anything can be assigned a global name with @code{define}: @lisp (define a 3) (define square (lambda (x) (* x x))) (square a) @result{} 9 @end lisp @item Procedures can be defined more concisely with the following syntax: @lisp (define (square x) (* x x)) @end lisp @item A list structure can be created with the @code{list} procedure: @lisp (list 2 a 5 7) @result{} (2 3 5 7) @end lisp @item Standard procedures are provided by the @code{(srfi srfi-1)} module to create and process lists (@pxref{SRFI-1, list processing,, guile, GNU Guile Reference Manual}). Here are some of the most useful ones in action: @lisp (use-modules (srfi srfi-1)) ;import list processing procedures (append (list 1 2) (list 3 4)) @result{} (1 2 3 4) (map (lambda (x) (* x x)) (list 1 2 3 4)) @result{} (1 4 9 16) (delete 3 (list 1 2 3 4)) @result{} (1 2 4) (filter odd? (list 1 2 3 4)) @result{} (1 3) (remove even? (list 1 2 3 4)) @result{} (1 3) (find number? (list "a" 42 "b")) @result{} 42 @end lisp Notice how the first argument to @code{map}, @code{filter}, @code{remove}, and @code{find} is a procedure! @item @cindex S-expression The @dfn{quote} disables evaluation of a parenthesized expression, also called an S-expression or ``s-exp'': the first term is not called over the other terms (@pxref{Expression Syntax, quote,, guile, GNU Guile Reference Manual}). Thus it effectively returns a list of terms. @lisp '(display (string-append "Hello " "Guix" "\n")) @result{} (display (string-append "Hello " "Guix" "\n")) '(2 a 5 7) @result{} (2 a 5 7) @end lisp @item The @code{quasiquote} (@code{`}, a backquote) disables evaluation of a parenthesized expression until @code{unquote} (@code{,}, a comma) re-enables it. Thus it provides us with fine-grained control over what is evaluated and what is not. @lisp `(2 a 5 7 (2 ,a 5 ,(+ a 4))) @result{} (2 a 5 7 (2 3 5 7)) @end lisp Note that the above result is a list of mixed elements: numbers, symbols (here @code{a}) and the last element is a list itself. @item @cindex G-expressions, syntax @cindex gexps, syntax @findex #~ @findex #$ @findex gexp @findex ungexp Guix defines a variant of S-expressions on steroids called @dfn{G-expressions} or ``gexps'', which come with a variant of @code{quasiquote} and @code{unquote}: @code{#~} (or @code{gexp}) and @code{#$} (or @code{ungexp}). They let you @emph{stage code for later execution}. For example, you'll encounter gexps in some package definitions where they provide code to be executed during the package build process. They look like this: @lisp (use-modules (guix gexp) ;so we can write gexps (gnu packages base)) ;for 'coreutils' ;; Below is a G-expression representing staged code. #~(begin ;; Invoke 'ls' from the package defined by the 'coreutils' ;; variable. (system* #$(file-append coreutils "/bin/ls") "-l") ;; Create this package's output directory. (mkdir #$output)) @end lisp @xref{G-Expressions,,, guix, GNU Guix Reference Manual}, for more on gexps. @item Multiple variables can be named locally with @code{let} (@pxref{Local Bindings,,, guile, GNU Guile Reference Manual}): @lisp (define x 10) (let ((x 2) (y 3)) (list x y)) @result{} (2 3) x @result{} 10 y @error{} In procedure module-lookup: Unbound variable: y @end lisp Use @code{let*} to allow later variable declarations to refer to earlier definitions. @lisp (let* ((x 2) (y (* x 3))) (list x y)) @result{} (2 6) @end lisp @item @dfn{Keywords} are typically used to identify the named parameters of a procedure. They are prefixed by @code{#:} (hash, colon) followed by alphanumeric characters: @code{#:like-this}. @xref{Keywords,,, guile, GNU Guile Reference Manual}. @item The percentage @code{%} is typically used for read-only global variables in the build stage. Note that it is merely a convention, like @code{_} in C. Scheme treats @code{%} exactly the same as any other letter. @item Modules are created with @code{define-module} (@pxref{Creating Guile Modules,,, guile, GNU Guile Reference Manual}). For instance @lisp (define-module (guix build-system ruby) #:use-module (guix store) #:export (ruby-build ruby-build-system)) @end lisp defines the module @code{guix build-system ruby} which must be located in @file{guix/build-system/ruby.scm} somewhere in the Guile load path. It depends on the @code{(guix store)} module and it exports two variables, @code{ruby-build} and @code{ruby-build-system}. @xref{Package Modules,,, guix, GNU Guix Reference Manual}, for info on modules that define packages. @end itemize @quotation Going further Scheme is a language that has been widely used to teach programming and you'll find plenty of material using it as a vehicle. Here's a selection of documents to learn more about Scheme: @itemize @item @uref{https://spritely.institute/static/papers/scheme-primer.html, @i{A Scheme Primer}}, by Christine Lemmer-Webber and the Spritely Institute. @item @uref{http://www.troubleshooters.com/codecorn/scheme_guile/hello.htm, @i{Scheme at a Glance}}, by Steve Litt. @item @c There used to be a copy at mitpress.mit.edu but it vanished. @uref{https://sarabander.github.io/sicp/, @i{Structure and Interpretation of Computer Programs}}, by Harold Abelson and Gerald Jay Sussman, with Julie Sussman. Colloquially known as ``SICP'', this book is a reference. You can also install it and read it from your computer: @example guix install sicp info-reader info sicp @end example @end itemize You'll find more books, tutorials and other resources at @url{https://schemers.org/}. @end quotation @c ********************************************************************* @node Packaging @chapter Packaging @cindex packaging This chapter is dedicated to teaching you how to add packages to the collection of packages that come with GNU Guix. This involves writing package definitions in Guile Scheme, organizing them in package modules, and building them. @menu * Packaging Tutorial:: A tutorial on how to add packages to Guix. @end menu @node Packaging Tutorial @section Packaging Tutorial GNU Guix stands out as the @emph{hackable} package manager, mostly because it uses @uref{https://www.gnu.org/software/guile/, GNU Guile}, a powerful high-level programming language, one of the @uref{https://en.wikipedia.org/wiki/Scheme_%28programming_language%29, Scheme} dialects from the @uref{https://en.wikipedia.org/wiki/Lisp_%28programming_language%29, Lisp family}. Package definitions are also written in Scheme, which empowers Guix in some very unique ways, unlike most other package managers that use shell scripts or simple languages. @itemize @item Use functions, structures, macros and all of Scheme expressiveness for your package definitions. @item Inheritance makes it easy to customize a package by inheriting from it and modifying only what is needed. @item Batch processing: the whole package collection can be parsed, filtered and processed. Building a headless server with all graphical interfaces stripped out? It's possible. Want to rebuild everything from source using specific compiler optimization flags? Pass the @code{#:make-flags "..."} argument to the list of packages. It wouldn't be a stretch to think @uref{https://wiki.gentoo.org/wiki/USE_flag, Gentoo USE flags} here, but this goes even further: the changes don't have to be thought out beforehand by the packager, they can be @emph{programmed} by the user! @end itemize The following tutorial covers all the basics around package creation with Guix. It does not assume much knowledge of the Guix system nor of the Lisp language. The reader is only expected to be familiar with the command line and to have some basic programming knowledge. @menu * A ``Hello World'' package:: * Setup:: * Extended example:: * Other build systems:: * Programmable and automated package definition:: * Getting help:: * Conclusion:: * References:: @end menu @node A ``Hello World'' package @subsection A ``Hello World'' package The ``Defining Packages'' section of the manual introduces the basics of Guix packaging (@pxref{Defining Packages,,, guix, GNU Guix Reference Manual}). In the following section, we will partly go over those basics again. GNU@tie{}Hello is a dummy project that serves as an idiomatic example for packaging. It uses the GNU build system (@code{./configure && make && make install}). Guix already provides a package definition which is a perfect example to start with. You can look up its declaration with @code{guix edit hello} from the command line. Let's see how it looks: @lisp (define-public hello (package (name "hello") (version "2.10") (source (origin (method url-fetch) (uri (string-append "mirror://gnu/hello/hello-" version ".tar.gz")) (sha256 (base32 "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i")))) (build-system gnu-build-system) (synopsis "Hello, GNU world: An example GNU package") (description "GNU Hello prints the message \"Hello, world!\" and then exits. It serves as an example of standard GNU coding practices. As such, it supports command-line arguments, multiple languages, and so on.") (home-page "https://www.gnu.org/software/hello/") (license gpl3+))) @end lisp As you can see, most of it is rather straightforward. But let's review the fields together: @table @samp @item name The project name. Using Scheme conventions, we prefer to keep it lower case, without underscore and using dash-separated words. @item source This field contains a description of the source code origin. The @code{origin} record contains these fields: @enumerate @item The method, here @code{url-fetch} to download via HTTP/FTP, but other methods exist, such as @code{git-fetch} for Git repositories. @item The URI, which is typically some @code{https://} location for @code{url-fetch}. Here the special `mirror://gnu` refers to a set of well known locations, all of which can be used by Guix to fetch the source, should some of them fail. @item The @code{sha256} checksum of the requested file. This is essential to ensure the source is not corrupted. Note that Guix works with base32 strings, hence the call to the @code{base32} function. @end enumerate @item build-system This is where the power of abstraction provided by the Scheme language really shines: in this case, the @code{gnu-build-system} abstracts away the famous @code{./configure && make && make install} shell invocations. Other build systems include the @code{trivial-build-system} which does not do anything and requires from the packager to program all the build steps, the @code{python-build-system}, the @code{emacs-build-system}, and many more (@pxref{Build Systems,,, guix, GNU Guix Reference Manual}). @item synopsis It should be a concise summary of what the package does. For many packages a tagline from the project's home page can be used as the synopsis. @item description Same as for the synopsis, it's fine to re-use the project description from the homepage. Note that Guix uses Texinfo syntax. @item home-page Use HTTPS if available. @item license See @code{guix/licenses.scm} in the project source for a full list of available licenses. @end table Time to build our first package! Nothing fancy here for now: we will stick to a dummy @code{my-hello}, a copy of the above declaration. As with the ritualistic ``Hello World'' taught with most programming languages, this will possibly be the most ``manual'' approach. We will work out an ideal setup later; for now we will go the simplest route. Save the following to a file @file{my-hello.scm}. @lisp (use-modules (guix packages) (guix download) (guix build-system gnu) (guix licenses)) (package (name "my-hello") (version "2.10") (source (origin (method url-fetch) (uri (string-append "mirror://gnu/hello/hello-" version ".tar.gz")) (sha256 (base32 "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i")))) (build-system gnu-build-system) (synopsis "Hello, Guix world: An example custom Guix package") (description "GNU Hello prints the message \"Hello, world!\" and then exits. It serves as an example of standard GNU coding practices. As such, it supports command-line arguments, multiple languages, and so on.") (home-page "https://www.gnu.org/software/hello/") (license gpl3+)) @end lisp We will explain the extra code in a moment. Feel free to play with the different values of the various fields. If you change the source, you'll need to update the checksum. Indeed, Guix refuses to build anything if the given checksum does not match the computed checksum of the source code. To obtain the correct checksum of the package declaration, we need to download the source, compute the sha256 checksum and convert it to base32. Thankfully, Guix can automate this task for us; all we need is to provide the URI: @c TRANSLATORS: This is example shell output. @example sh $ guix download mirror://gnu/hello/hello-2.10.tar.gz Starting download of /tmp/guix-file.JLYgL7 From https://ftpmirror.gnu.org/gnu/hello/hello-2.10.tar.gz... following redirection to `https://mirror.ibcp.fr/pub/gnu/hello/hello-2.10.tar.gz'... …10.tar.gz 709KiB 2.5MiB/s 00:00 [##################] 100.0% /gnu/store/hbdalsf5lpf01x4dcknwx6xbn6n5km6k-hello-2.10.tar.gz 0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i @end example In this specific case the output tells us which mirror was chosen. If the result of the above command is not the same as in the above snippet, update your @code{my-hello} declaration accordingly. Note that GNU package tarballs come with an OpenPGP signature, so you should definitely check the signature of this tarball with `gpg` to authenticate it before going further: @c TRANSLATORS: This is example shell output. @example sh $ guix download mirror://gnu/hello/hello-2.10.tar.gz.sig Starting download of /tmp/guix-file.03tFfb From https://ftpmirror.gnu.org/gnu/hello/hello-2.10.tar.gz.sig... following redirection to `https://ftp.igh.cnrs.fr/pub/gnu/hello/hello-2.10.tar.gz.sig'... ….tar.gz.sig 819B 1.2MiB/s 00:00 [##################] 100.0% /gnu/store/rzs8wba9ka7grrmgcpfyxvs58mly0sx6-hello-2.10.tar.gz.sig 0q0v86n3y38z17rl146gdakw9xc4mcscpk8dscs412j22glrv9jf $ gpg --verify /gnu/store/rzs8wba9ka7grrmgcpfyxvs58mly0sx6-hello-2.10.tar.gz.sig /gnu/store/hbdalsf5lpf01x4dcknwx6xbn6n5km6k-hello-2.10.tar.gz gpg: Signature made Sun 16 Nov 2014 01:08:37 PM CET gpg: using RSA key A9553245FDE9B739 gpg: Good signature from "Sami Kerola " [unknown] gpg: aka "Sami Kerola (http://www.iki.fi/kerolasa/) " [unknown] gpg: WARNING: This key is not certified with a trusted signature! gpg: There is no indication that the signature belongs to the owner. Primary key fingerprint: 8ED3 96E3 7E38 D471 A005 30D3 A955 3245 FDE9 B739 @end example You can then happily run @c TRANSLATORS: Do not translate this command @example sh $ guix package --install-from-file=my-hello.scm @end example You should now have @code{my-hello} in your profile! @c TRANSLATORS: Do not translate this command @example sh $ guix package --list-installed=my-hello my-hello 2.10 out /gnu/store/f1db2mfm8syb8qvc357c53slbvf1g9m9-my-hello-2.10 @end example We've gone as far as we could without any knowledge of Scheme. Before moving on to more complex packages, now is the right time to brush up on your Scheme knowledge. @pxref{A Scheme Crash Course} to get up to speed. @node Setup @subsection Setup In the rest of this chapter we will rely on some basic Scheme programming knowledge. Now let's detail the different possible setups for working on Guix packages. There are several ways to set up a Guix packaging environment. We recommend you work directly on the Guix source checkout since it makes it easier for everyone to contribute to the project. But first, let's look at other possibilities. @menu * Local file:: * Channels:: * Direct checkout hacking:: @end menu @node Local file @subsubsection Local file This is what we previously did with @samp{my-hello}. With the Scheme basics we've covered, we are now able to explain the leading chunks. As stated in @code{guix package --help}: @example -f, --install-from-file=FILE install the package that the code within FILE evaluates to @end example Thus the last expression @emph{must} return a package, which is the case in our earlier example. The @code{use-modules} expression tells which of the modules we need in the file. Modules are a collection of values and procedures. They are commonly called ``libraries'' or ``packages'' in other programming languages. @node Channels @subsubsection Channels @cindex channel Guix and its package collection can be extended through @dfn{channels}. A channel is a Git repository, public or not, containing @file{.scm} files that provide packages (@pxref{Defining Packages,,, guix, GNU Guix Reference Manual}) or services (@pxref{Defining Services,,, guix, GNU Guix Reference Manual}). How would you go about creating a channel? First, create a directory that will contain your @file{.scm} files, say @file{~/my-channel}: @example mkdir ~/my-channel @end example Suppose you want to add the @samp{my-hello} package we saw previously; it first needs some adjustments: @lisp (define-module (my-hello) #:use-module (guix licenses) #:use-module (guix packages) #:use-module (guix build-system gnu) #:use-module (guix download)) (define-public my-hello (package (name "my-hello") (version "2.10") (source (origin (method url-fetch) (uri (string-append "mirror://gnu/hello/hello-" version ".tar.gz")) (sha256 (base32 "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i")))) (build-system gnu-build-system) (synopsis "Hello, Guix world: An example custom Guix package") (description "GNU Hello prints the message \"Hello, world!\" and then exits. It serves as an example of standard GNU coding practices. As such, it supports command-line arguments, multiple languages, and so on.") (home-page "https://www.gnu.org/software/hello/") (license gpl3+))) @end lisp Note that we have assigned the package value to an exported variable name with @code{define-public}. This is effectively assigning the package to the @code{my-hello} variable so that it can be referenced, among other as dependency of other packages. If you use @code{guix package --install-from-file=my-hello.scm} on the above file, it will fail because the last expression, @code{define-public}, does not return a package. If you want to use @code{define-public} in this use-case nonetheless, make sure the file ends with an evaluation of @code{my-hello}: @lisp ;; ... (define-public my-hello ;; ... ) my-hello @end lisp This last example is not very typical. Now how do you make that package visible to @command{guix} commands so you can test your packages? You need to add the directory to the search path using the @option{-L} command-line option, as in these examples: @example guix show -L ~/my-channel my-hello guix build -L ~/my-channel my-hello @end example The final step is to turn @file{~/my-channel} into an actual channel, making your package collection seamlessly available @i{via} any @command{guix} command. To do that, you first need to make it a Git repository: @example cd ~/my-channel git init git add my-hello.scm git commit -m "First commit of my channel." @end example And that's it, you have a channel! From there on, you can add this channel to your channel configuration in @file{~/.config/guix/channels.scm} (@pxref{Specifying Additional Channels,,, guix, GNU Guix Reference Manual}); assuming you keep your channel local for now, the @file{channels.scm} would look something like this: @lisp (append (list (channel (name 'my-channel) (url (string-append "file://" (getenv "HOME") "/my-channel")))) %default-channels) @end lisp Next time you run @command{guix pull}, your channel will be picked up and the packages it defines will be readily available to all the @command{guix} commands, even if you do not pass @option{-L}. The @command{guix describe} command will show that Guix is, indeed, using both the @code{my-channel} and the @code{guix} channels. @xref{Creating a Channel,,, guix, GNU Guix Reference Manual}, for details. @node Direct checkout hacking @subsubsection Direct checkout hacking Working directly on the Guix project is recommended: it reduces the friction when the time comes to submit your changes upstream to let the community benefit from your hard work! Unlike most software distributions, the Guix repository holds in one place both the tooling (including the package manager) and the package definitions. This choice was made so that it would give developers the flexibility to modify the API without breakage by updating all packages at the same time. This reduces development inertia. Check out the official @uref{https://git-scm.com/, Git} repository: @example $ git clone https://git.savannah.gnu.org/git/guix.git @end example In the rest of this article, we use @samp{$GUIX_CHECKOUT} to refer to the location of the checkout. Follow the instructions in the manual (@pxref{Contributing,,, guix, GNU Guix Reference Manual}) to set up the repository environment. Once ready, you should be able to use the package definitions from the repository environment. Feel free to edit package definitions found in @samp{$GUIX_CHECKOUT/gnu/packages}. The @samp{$GUIX_CHECKOUT/pre-inst-env} script lets you use @samp{guix} over the package collection of the repository (@pxref{Running Guix Before It Is Installed,,, guix, GNU Guix Reference Manual}). @itemize @item Search packages, such as Ruby: @example $ cd $GUIX_CHECKOUT $ ./pre-inst-env guix package --list-available=ruby ruby 1.8.7-p374 out gnu/packages/ruby.scm:119:2 ruby 2.1.6 out gnu/packages/ruby.scm:91:2 ruby 2.2.2 out gnu/packages/ruby.scm:39:2 @end example @item Build a package, here Ruby version 2.1: @example $ ./pre-inst-env guix build --keep-failed ruby@@2.1 /gnu/store/c13v73jxmj2nir2xjqaz5259zywsa9zi-ruby-2.1.6 @end example @item Install it to your user profile: @example $ ./pre-inst-env guix package --install ruby@@2.1 @end example @item Check for common mistakes: @example $ ./pre-inst-env guix lint ruby@@2.1 @end example @end itemize Guix strives at maintaining a high packaging standard; when contributing to the Guix project, remember to @itemize @item follow the coding style (@pxref{Coding Style,,, guix, GNU Guix Reference Manual}), @item and review the check list from the manual (@pxref{Submitting Patches,,, guix, GNU Guix Reference Manual}). @end itemize Once you are happy with the result, you are welcome to send your contribution to make it part of Guix. This process is also detailed in the manual. (@pxref{Contributing,,, guix, GNU Guix Reference Manual}) It's a community effort so the more join in, the better Guix becomes! @node Extended example @subsection Extended example The above ``Hello World'' example is as simple as it goes. Packages can be more complex than that and Guix can handle more advanced scenarios. Let's look at another, more sophisticated package (slightly modified from the source): @lisp (define-module (gnu packages version-control) #:use-module ((guix licenses) #:prefix license:) #:use-module (guix utils) #:use-module (guix packages) #:use-module (guix git-download) #:use-module (guix build-system cmake) #:use-module (gnu packages compression) #:use-module (gnu packages pkg-config) #:use-module (gnu packages python) #:use-module (gnu packages ssh) #:use-module (gnu packages tls) #:use-module (gnu packages web)) (define-public my-libgit2 (let ((commit "e98d0a37c93574d2c6107bf7f31140b548c6a7bf") (revision "1")) (package (name "my-libgit2") (version (git-version "0.26.6" revision commit)) (source (origin (method git-fetch) (uri (git-reference (url "https://github.com/libgit2/libgit2/") (commit commit))) (file-name (git-file-name name version)) (sha256 (base32 "17pjvprmdrx4h6bb1hhc98w9qi6ki7yl57f090n9kbhswxqfs7s3")) (patches (search-patches "libgit2-mtime-0.patch")) (modules '((guix build utils))) ;; Remove bundled software. (snippet '(delete-file-recursively "deps")))) (build-system cmake-build-system) (outputs '("out" "debug")) (arguments `(#:tests? #true ; Run the test suite (this is the default) #:configure-flags '("-DUSE_SHA1DC=ON") ; SHA-1 collision detection #:phases (modify-phases %standard-phases (add-after 'unpack 'fix-hardcoded-paths (lambda _ (substitute* "tests/repo/init.c" (("#!/bin/sh") (string-append "#!" (which "sh")))) (substitute* "tests/clar/fs.h" (("/bin/cp") (which "cp")) (("/bin/rm") (which "rm"))))) ;; Run checks more verbosely. (replace 'check (lambda* (#:key tests? #:allow-other-keys) (when tests? (invoke "./libgit2_clar" "-v" "-Q")))) (add-after 'unpack 'make-files-writable-for-tests (lambda _ (for-each make-file-writable (find-files "."))))))) (inputs (list libssh2 http-parser python-wrapper)) (native-inputs (list pkg-config)) (propagated-inputs ;; These two libraries are in 'Requires.private' in libgit2.pc. (list openssl zlib)) (home-page "https://libgit2.github.com/") (synopsis "Library providing Git core methods") (description "Libgit2 is a portable, pure C implementation of the Git core methods provided as a re-entrant linkable library with a solid API, allowing you to write native speed custom Git applications in any language with bindings.") ;; GPLv2 with linking exception (license license:gpl2)))) @end lisp (In those cases were you only want to tweak a few fields from a package definition, you should rely on inheritance instead of copy-pasting everything. See below.) Let's discuss those fields in depth. @subsubsection @code{git-fetch} method Unlike the @code{url-fetch} method, @code{git-fetch} expects a @code{git-reference} which takes a Git repository and a commit. The commit can be any Git reference such as tags, so if the @code{version} is tagged, then it can be used directly. Sometimes the tag is prefixed with a @code{v}, in which case you'd use @code{(commit (string-append "v" version))}. To ensure that the source code from the Git repository is stored in a directory with a descriptive name, we use @code{(file-name (git-file-name name version))}. The @code{git-version} procedure can be used to derive the version when packaging programs for a specific commit, following the Guix contributor guidelines (@pxref{Version Numbers,,, guix, GNU Guix Reference Manual}). How does one obtain the @code{sha256} hash that's in there, you ask? By invoking @command{guix hash} on a checkout of the desired commit, along these lines: @example git clone https://github.com/libgit2/libgit2/ cd libgit2 git checkout v0.26.6 guix hash -rx . @end example @command{guix hash -rx} computes a SHA256 hash over the whole directory, excluding the @file{.git} sub-directory (@pxref{Invoking guix hash,,, guix, GNU Guix Reference Manual}). In the future, @command{guix download} will hopefully be able to do these steps for you, just like it does for regular downloads. @subsubsection Snippets Snippets are quoted (i.e. non-evaluated) Scheme code that are a means of patching the source. They are a Guix-y alternative to the traditional @file{.patch} files. Because of the quote, the code in only evaluated when passed to the Guix daemon for building. There can be as many snippets as needed. Snippets might need additional Guile modules which can be imported from the @code{modules} field. @subsubsection Inputs There are 3 different input types. In short: @table @asis @item native-inputs Required for building but not runtime -- installing a package through a substitute won't install these inputs. @item inputs Installed in the store but not in the profile, as well as being present at build time. @item propagated-inputs Installed in the store and in the profile, as well as being present at build time. @end table @xref{package Reference,,, guix, GNU Guix Reference Manual} for more details. The distinction between the various inputs is important: if a dependency can be handled as an @emph{input} instead of a @emph{propagated input}, it should be done so, or else it ``pollutes'' the user profile for no good reason. For instance, a user installing a graphical program that depends on a command line tool might only be interested in the graphical part, so there is no need to force the command line tool into the user profile. The dependency is a concern to the package, not to the user. @emph{Inputs} make it possible to handle dependencies without bugging the user by adding undesired executable files (or libraries) to their profile. Same goes for @emph{native-inputs}: once the program is installed, build-time dependencies can be safely garbage-collected. It also matters when a substitute is available, in which case only the @emph{inputs} and @emph{propagated inputs} will be fetched: the @emph{native inputs} are not required to install a package from a substitute. @quotation Note You may see here and there snippets where package inputs are written quite differently, like so: @lisp ;; The "old style" for inputs. (inputs `(("libssh2" ,libssh2) ("http-parser" ,http-parser) ("python" ,python-wrapper))) @end lisp This is the ``old style'', where each input in the list is explicitly given a label (a string). It is still supported but we recommend using the style above instead. @xref{package Reference,,, guix, GNU Guix Reference Manual}, for more info. @end quotation @subsubsection Outputs Just like how a package can have multiple inputs, it can also produce multiple outputs. Each output corresponds to a separate directory in the store. The user can choose which output to install; this is useful to save space or to avoid polluting the user profile with unwanted executables or libraries. Output separation is optional. When the @code{outputs} field is left out, the default and only output (the complete package) is referred to as @code{"out"}. Typical separate output names include @code{debug} and @code{doc}. It's advised to separate outputs only when you've shown it's worth it: if the output size is significant (compare with @code{guix size}) or in case the package is modular. @subsubsection Build system arguments The @code{arguments} is a keyword-value list used to configure the build process. The simplest argument @code{#:tests?} can be used to disable the test suite when building the package. This is mostly useful when the package does not feature any test suite. It's strongly recommended to keep the test suite on if there is one. Another common argument is @code{:make-flags}, which specifies a list of flags to append when running make, as you would from the command line. For instance, the following flags @lisp #:make-flags (list (string-append "prefix=" (assoc-ref %outputs "out")) "CC=gcc") @end lisp translate into @example $ make CC=gcc prefix=/gnu/store/...- @end example This sets the C compiler to @code{gcc} and the @code{prefix} variable (the installation directory in Make parlance) to @code{(assoc-ref %outputs "out")}, which is a build-stage global variable pointing to the destination directory in the store (something like @file{/gnu/store/...-my-libgit2-20180408}). Similarly, it's possible to set the configure flags: @lisp #:configure-flags '("-DUSE_SHA1DC=ON") @end lisp The @code{%build-inputs} variable is also generated in scope. It's an association table that maps the input names to their store directories. The @code{phases} keyword lists the sequential steps of the build system. Typically phases include @code{unpack}, @code{configure}, @code{build}, @code{install} and @code{check}. To know more about those phases, you need to work out the appropriate build system definition in @samp{$GUIX_CHECKOUT/guix/build/gnu-build-system.scm}: @lisp (define %standard-phases ;; Standard build phases, as a list of symbol/procedure pairs. (let-syntax ((phases (syntax-rules () ((_ p ...) `((p . ,p) ...))))) (phases set-SOURCE-DATE-EPOCH set-paths install-locale unpack bootstrap patch-usr-bin-file patch-source-shebangs configure patch-generated-file-shebangs build check install patch-shebangs strip validate-runpath validate-documentation-location delete-info-dir-file patch-dot-desktop-files install-license-files reset-gzip-timestamps compress-documentation))) @end lisp Or from the REPL: @lisp (add-to-load-path "/path/to/guix/checkout") ,use (guix build gnu-build-system) (map first %standard-phases) @result{} (set-SOURCE-DATE-EPOCH set-paths install-locale unpack bootstrap patch-usr-bin-file patch-source-shebangs configure patch-generated-file-shebangs build check install patch-shebangs strip validate-runpath validate-documentation-location delete-info-dir-file patch-dot-desktop-files install-license-files reset-gzip-timestamps compress-documentation) @end lisp If you want to know more about what happens during those phases, consult the associated procedures. For instance, as of this writing the definition of @code{unpack} for the GNU build system is: @lisp (define* (unpack #:key source #:allow-other-keys) "Unpack SOURCE in the working directory, and change directory within the source. When SOURCE is a directory, copy it in a sub-directory of the current working directory." (if (file-is-directory? source) (begin (mkdir "source") (chdir "source") ;; Preserve timestamps (set to the Epoch) on the copied tree so that ;; things work deterministically. (copy-recursively source "." #:keep-mtime? #true)) (begin (if (string-suffix? ".zip" source) (invoke "unzip" source) (invoke "tar" "xvf" source)) (chdir (first-subdirectory ".")))) #true) @end lisp Note the @code{chdir} call: it changes the working directory to where the source was unpacked. Thus every phase following the @code{unpack} will use the source as a working directory, which is why we can directly work on the source files. That is to say, unless a later phase changes the working directory to something else. We modify the list of @code{%standard-phases} of the build system with the @code{modify-phases} macro as per the list of specified modifications, which may have the following forms: @itemize @item @code{(add-before @var{phase} @var{new-phase} @var{procedure})}: Run @var{procedure} named @var{new-phase} before @var{phase}. @item @code{(add-after @var{phase} @var{new-phase} @var{procedure})}: Same, but afterwards. @item @code{(replace @var{phase} @var{procedure})}. @item @code{(delete @var{phase})}. @end itemize The @var{procedure} supports the keyword arguments @code{inputs} and @code{outputs}. Each input (whether @emph{native}, @emph{propagated} or not) and output directory is referenced by their name in those variables. Thus @code{(assoc-ref outputs "out")} is the store directory of the main output of the package. A phase procedure may look like this: @lisp (lambda* (#:key inputs outputs #:allow-other-keys) (let ((bash-directory (assoc-ref inputs "bash")) (output-directory (assoc-ref outputs "out")) (doc-directory (assoc-ref outputs "doc"))) ;; ... #true)) @end lisp The procedure must return @code{#true} on success. It's brittle to rely on the return value of the last expression used to tweak the phase because there is no guarantee it would be a @code{#true}. Hence the trailing @code{#true} to ensure the right value is returned on success. @subsubsection Code staging The astute reader may have noticed the quasi-quote and comma syntax in the argument field. Indeed, the build code in the package declaration should not be evaluated on the client side, but only when passed to the Guix daemon. This mechanism of passing code around two running processes is called @uref{https://arxiv.org/abs/1709.00833, code staging}. @subsubsection Utility functions When customizing @code{phases}, we often need to write code that mimics the equivalent system invocations (@code{make}, @code{mkdir}, @code{cp}, etc.)@: commonly used during regular ``Unix-style'' installations. Some like @code{chmod} are native to Guile. @xref{,,, guile, Guile reference manual} for a complete list. Guix provides additional helper functions which prove especially handy in the context of package management. Some of those functions can be found in @samp{$GUIX_CHECKOUT/guix/guix/build/utils.scm}. Most of them mirror the behaviour of the traditional Unix system commands: @table @code @item which Like the @samp{which} system command. @item find-files Akin to the @samp{find} system command. @item mkdir-p Like @samp{mkdir -p}, which creates all parents as needed. @item install-file Similar to @samp{install} when installing a file to a (possibly non-existing) directory. Guile has @code{copy-file} which works like @samp{cp}. @item copy-recursively Like @samp{cp -r}. @item delete-file-recursively Like @samp{rm -rf}. @item invoke Run an executable. This should be used instead of @code{system*}. @item with-directory-excursion Run the body in a different working directory, then restore the previous working directory. @item substitute* A ``@command{sed}-like'' function. @end table @xref{Build Utilities,,, guix, GNU Guix Reference Manual}, for more information on these utilities. @subsubsection Module prefix The license in our last example needs a prefix: this is because of how the @code{license} module was imported in the package, as @code{#:use-module ((guix licenses) #:prefix license:)}. The Guile module import mechanism (@pxref{Using Guile Modules,,, guile, Guile reference manual}) gives the user full control over namespacing: this is needed to avoid clashes between, say, the @samp{zlib} variable from @samp{licenses.scm} (a @emph{license} value) and the @samp{zlib} variable from @samp{compression.scm} (a @emph{package} value). @node Other build systems @subsection Other build systems What we've seen so far covers the majority of packages using a build system other than the @code{trivial-build-system}. The latter does not automate anything and leaves you to build everything manually. This can be more demanding and we won't cover it here for now, but thankfully it is rarely necessary to fall back on this system. For the other build systems, such as ASDF, Emacs, Perl, Ruby and many more, the process is very similar to the GNU build system except for a few specialized arguments. @xref{Build Systems,,, guix, GNU Guix Reference Manual}, for more information on build systems, or check the source code in the @samp{$GUIX_CHECKOUT/guix/build} and @samp{$GUIX_CHECKOUT/guix/build-system} directories. @node Programmable and automated package definition @subsection Programmable and automated package definition We can't repeat it enough: having a full-fledged programming language at hand empowers us in ways that reach far beyond traditional package management. Let's illustrate this with some awesome features of Guix! @menu * Recursive importers:: * Automatic update:: * Inheritance:: @end menu @node Recursive importers @subsubsection Recursive importers You might find some build systems good enough that there is little to do at all to write a package, to the point that it becomes repetitive and tedious after a while. A @emph{raison d'être} of computers is to replace human beings at those boring tasks. So let's tell Guix to do this for us and create the package definition of an R package from CRAN (the output is trimmed for conciseness): @example $ guix import cran --recursive walrus (define-public r-mc2d ; ... (license gpl2+))) (define-public r-jmvcore ; ... (license gpl2+))) (define-public r-wrs2 ; ... (license gpl3))) (define-public r-walrus (package (name "r-walrus") (version "1.0.3") (source (origin (method url-fetch) (uri (cran-uri "walrus" version)) (sha256 (base32 "1nk2glcvy4hyksl5ipq2mz8jy4fss90hx6cq98m3w96kzjni6jjj")))) (build-system r-build-system) (propagated-inputs (list r-ggplot2 r-jmvcore r-r6 r-wrs2)) (home-page "https://github.com/jamovi/walrus") (synopsis "Robust Statistical Methods") (description "This package provides a toolbox of common robust statistical tests, including robust descriptives, robust t-tests, and robust ANOVA. It is also available as a module for 'jamovi' (see for more information). Walrus is based on the WRS2 package by Patrick Mair, which is in turn based on the scripts and work of Rand Wilcox. These analyses are described in depth in the book 'Introduction to Robust Estimation & Hypothesis Testing'.") (license gpl3))) @end example The recursive importer won't import packages for which Guix already has package definitions, except for the very first. Not all applications can be packaged this way, only those relying on a select number of supported systems. Read about the full list of importers in the guix import section of the manual (@pxref{Invoking guix import,,, guix, GNU Guix Reference Manual}). @node Automatic update @subsubsection Automatic update Guix can be smart enough to check for updates on systems it knows. It can report outdated package definitions with @example $ guix refresh hello @end example In most cases, updating a package to a newer version requires little more than changing the version number and the checksum. Guix can do that automatically as well: @example $ guix refresh hello --update @end example @node Inheritance @subsubsection Inheritance If you've started browsing the existing package definitions, you might have noticed that a significant number of them have a @code{inherit} field: @lisp (define-public adwaita-icon-theme (package (inherit gnome-icon-theme) (name "adwaita-icon-theme") (version "3.26.1") (source (origin (method url-fetch) (uri (string-append "mirror://gnome/sources/" name "/" (version-major+minor version) "/" name "-" version ".tar.xz")) (sha256 (base32 "17fpahgh5dyckgz7rwqvzgnhx53cx9kr2xw0szprc6bnqy977fi8")))) (native-inputs (list `(,gtk+ "bin"))))) @end lisp All unspecified fields are inherited from the parent package. This is very convenient to create alternative packages, for instance with different source, version or compilation options. @node Getting help @subsection Getting help Sadly, some applications can be tough to package. Sometimes they need a patch to work with the non-standard file system hierarchy enforced by the store. Sometimes the tests won't run properly. (They can be skipped but this is not recommended.) Other times the resulting package won't be reproducible. Should you be stuck, unable to figure out how to fix any sort of packaging issue, don't hesitate to ask the community for help. See the @uref{https://www.gnu.org/software/guix/contact/, Guix homepage} for information on the mailing lists, IRC, etc. @node Conclusion @subsection Conclusion This tutorial was a showcase of the sophisticated package management that Guix boasts. At this point we have mostly restricted this introduction to the @code{gnu-build-system} which is a core abstraction layer on which more advanced abstractions are based. Where do we go from here? Next we ought to dissect the innards of the build system by removing all abstractions, using the @code{trivial-build-system}: this should give us a thorough understanding of the process before investigating some more advanced packaging techniques and edge cases. Other features worth exploring are the interactive editing and debugging capabilities of Guix provided by the Guile REPL@. Those fancy features are completely optional and can wait; now is a good time to take a well-deserved break. With what we've introduced here you should be well armed to package lots of programs. You can get started right away and hopefully we will see your contributions soon! @node References @subsection References @itemize @item The @uref{https://www.gnu.org/software/guix/manual/en/html_node/Defining-Packages.html, package reference in the manual} @item @uref{https://gitlab.com/pjotrp/guix-notes/blob/master/HACKING.org, Pjotr’s hacking guide to GNU Guix} @item @uref{https://www.gnu.org/software/guix/guix-ghm-andreas-20130823.pdf, ``GNU Guix: Package without a scheme!''}, by Andreas Enge @end itemize @c ********************************************************************* @node System Configuration @chapter System Configuration Guix offers a flexible language for declaratively configuring your Guix System. This flexibility can at times be overwhelming. The purpose of this chapter is to demonstrate some advanced configuration concepts. @pxref{System Configuration,,, guix, GNU Guix Reference Manual} for a complete reference. @menu * Auto-Login to a Specific TTY:: Automatically Login a User to a Specific TTY * Customizing the Kernel:: Creating and using a custom Linux kernel on Guix System. * Guix System Image API:: Customizing images to target specific platforms. * Using security keys:: How to use security keys with Guix System. * Dynamic DNS mcron job:: Job to update the IP address behind a DuckDNS host name. * Connecting to Wireguard VPN:: Connecting to a Wireguard VPN. * Customizing a Window Manager:: Handle customization of a Window manager on Guix System. * Running Guix on a Linode Server:: Running Guix on a Linode Server. * Running Guix on a Kimsufi Server:: Running Guix on a Kimsufi Server. * Setting up a bind mount:: Setting up a bind mount in the file-systems definition. * Getting substitutes from Tor:: Configuring Guix daemon to get substitutes through Tor. * Setting up NGINX with Lua:: Configuring NGINX web-server to load Lua modules. * Music Server with Bluetooth Audio:: Headless music player with Bluetooth output. @end menu @node Auto-Login to a Specific TTY @section Auto-Login to a Specific TTY While the Guix manual explains auto-login one user to @emph{all} TTYs ( @pxref{auto-login to TTY,,, guix, GNU Guix Reference Manual}), some might prefer a situation, in which one user is logged into one TTY with the other TTYs either configured to login different users or no one at all. Note that one can auto-login one user to any TTY, but it is usually advisable to avoid @code{tty1}, which, by default, is used to log warnings and errors. Here is how one might set up auto login for one user to one tty: @lisp (define (auto-login-to-tty config tty user) (if (string=? tty (mingetty-configuration-tty config)) (mingetty-configuration (inherit config) (auto-login user)) config)) (define %my-services (modify-services %base-services ;; @dots{} (mingetty-service-type config => (auto-login-to-tty config "tty3" "alice")))) (operating-system ;; @dots{} (services %my-services)) @end lisp One could also @code{compose} (@pxref{Higher-Order Functions,,, guile, The Guile Reference Manual}) @code{auto-login-to-tty} to login multiple users to multiple ttys. Finally, here is a note of caution. Setting up auto login to a TTY, means that anyone can turn on your computer and run commands as your regular user. However, if you have an encrypted root partition, and thus already need to enter a passphrase when the system boots, auto-login might be a convenient option. @node Customizing the Kernel @section Customizing the Kernel Guix is, at its core, a source based distribution with substitutes (@pxref{Substitutes,,, guix, GNU Guix Reference Manual}), and as such building packages from their source code is an expected part of regular package installations and upgrades. Given this starting point, it makes sense that efforts are made to reduce the amount of time spent compiling packages, and recent changes and upgrades to the building and distribution of substitutes continues to be a topic of discussion within Guix. The kernel, while not requiring an overabundance of RAM to build, does take a rather long time on an average machine. The official kernel configuration, as is the case with many GNU/Linux distributions, errs on the side of inclusiveness, and this is really what causes the build to take such a long time when the kernel is built from source. The Linux kernel, however, can also just be described as a regular old package, and as such can be customized just like any other package. The procedure is a little bit different, although this is primarily due to the nature of how the package definition is written. The @code{linux-libre} kernel package definition is actually a procedure which creates a package. @lisp (define* (make-linux-libre* version gnu-revision source supported-systems #:key (extra-version #f) ;; A function that takes an arch and a variant. ;; See kernel-config for an example. (configuration-file #f) (defconfig "defconfig") (extra-options %default-extra-linux-options)) ...) @end lisp The current @code{linux-libre} package is for the 5.15.x series, and is declared like this: @lisp (define-public linux-libre-5.15 (make-linux-libre* linux-libre-5.15-version linux-libre-5.15-gnu-revision linux-libre-5.15-source '("x86_64-linux" "i686-linux" "armhf-linux" "aarch64-linux" "riscv64-linux") #:configuration-file kernel-config)) @end lisp Any keys which are not assigned values inherit their default value from the @code{make-linux-libre} definition. When comparing the two snippets above, notice the code comment that refers to @code{#:configuration-file}. Because of this, it is not actually easy to include a custom kernel configuration from the definition, but don't worry, there are other ways to work with what we do have. There are two ways to create a kernel with a custom kernel configuration. The first is to provide a standard @file{.config} file during the build process by including an actual @file{.config} file as a native input to our custom kernel. The following is a snippet from the custom @code{'configure} phase of the @code{make-linux-libre} package definition: @lisp (let ((build (assoc-ref %standard-phases 'build)) (config (assoc-ref (or native-inputs inputs) "kconfig"))) ;; Use a custom kernel configuration file or a default ;; configuration file. (if config (begin (copy-file config ".config") (chmod ".config" #o666)) (invoke "make" ,defconfig))) @end lisp Below is a sample kernel package. The @code{linux-libre} package is nothing special and can be inherited from and have its fields overridden like any other package: @lisp (define-public linux-libre/E2140 (package (inherit linux-libre) (native-inputs `(("kconfig" ,(local-file "E2140.config")) ,@@(alist-delete "kconfig" (package-native-inputs linux-libre)))))) @end lisp In the same directory as the file defining @code{linux-libre-E2140} is a file named @file{E2140.config}, which is an actual kernel configuration file. The @code{defconfig} keyword of @code{make-linux-libre} is left blank here, so the only kernel configuration in the package is the one which was included in the @code{native-inputs} field. The second way to create a custom kernel is to pass a new value to the @code{extra-options} keyword of the @code{make-linux-libre} procedure. The @code{extra-options} keyword works with another function defined right below it: @lisp (define %default-extra-linux-options `(;; https://lists.gnu.org/archive/html/guix-devel/2014-04/msg00039.html ("CONFIG_DEVPTS_MULTIPLE_INSTANCES" . #true) ;; Modules required for initrd: ("CONFIG_NET_9P" . m) ("CONFIG_NET_9P_VIRTIO" . m) ("CONFIG_VIRTIO_BLK" . m) ("CONFIG_VIRTIO_NET" . m) ("CONFIG_VIRTIO_PCI" . m) ("CONFIG_VIRTIO_BALLOON" . m) ("CONFIG_VIRTIO_MMIO" . m) ("CONFIG_FUSE_FS" . m) ("CONFIG_CIFS" . m) ("CONFIG_9P_FS" . m))) (define (config->string options) (string-join (map (match-lambda ((option . 'm) (string-append option "=m")) ((option . #true) (string-append option "=y")) ((option . #false) (string-append option "=n"))) options) "\n")) @end lisp And in the custom configure script from the `make-linux-libre` package: @lisp ;; Appending works even when the option wasn't in the ;; file. The last one prevails if duplicated. (let ((port (open-file ".config" "a")) (extra-configuration ,(config->string extra-options))) (display extra-configuration port) (close-port port)) (invoke "make" "oldconfig") @end lisp So by not providing a configuration-file the @file{.config} starts blank, and then we write into it the collection of flags that we want. Here's another custom kernel: @lisp (define %macbook41-full-config (append %macbook41-config-options %file-systems %efi-support %emulation (@@@@ (gnu packages linux) %default-extra-linux-options))) (define-public linux-libre-macbook41 ;; XXX: Access the internal 'make-linux-libre*' procedure, which is ;; private and unexported, and is liable to change in the future. ((@@@@ (gnu packages linux) make-linux-libre*) (@@@@ (gnu packages linux) linux-libre-version) (@@@@ (gnu packages linux) linux-libre-gnu-revision) (@@@@ (gnu packages linux) linux-libre-source) '("x86_64-linux") #:extra-version "macbook41" #:extra-options %macbook41-config-options)) @end lisp In the above example @code{%file-systems} is a collection of flags enabling different file system support, @code{%efi-support} enables EFI support and @code{%emulation} enables a x86_64-linux machine to act in 32-bit mode also. @code{%default-extra-linux-options} are the ones quoted above, which had to be added in since they were replaced in the @code{extra-options} keyword. This all sounds like it should be doable, but how does one even know which modules are required for a particular system? Two places that can be helpful in trying to answer this question is the @uref{https://wiki.gentoo.org/wiki/Handbook:AMD64/Installation/Kernel, Gentoo Handbook} and the @uref{https://www.kernel.org/doc/html/latest/admin-guide/README.html?highlight=localmodconfig, documentation from the kernel itself}. From the kernel documentation, it seems that @code{make localmodconfig} is the command we want. In order to actually run @code{make localmodconfig} we first need to get and unpack the kernel source code: @example shell tar xf $(guix build linux-libre --source) @end example Once inside the directory containing the source code run @code{touch .config} to create an initial, empty @file{.config} to start with. @code{make localmodconfig} works by seeing what you already have in @file{.config} and letting you know what you're missing. If the file is blank then you're missing everything. The next step is to run: @example shell guix shell -D linux-libre -- make localmodconfig @end example and note the output. Do note that the @file{.config} file is still empty. The output generally contains two types of warnings. The first start with "WARNING" and can actually be ignored in our case. The second read: @example shell module pcspkr did not have configs CONFIG_INPUT_PCSPKR @end example For each of these lines, copy the @code{CONFIG_XXXX_XXXX} portion into the @file{.config} in the directory, and append @code{=m}, so in the end it looks like this: @example shell CONFIG_INPUT_PCSPKR=m CONFIG_VIRTIO=m @end example After copying all the configuration options, run @code{make localmodconfig} again to make sure that you don't have any output starting with ``module''. After all of these machine specific modules there are a couple more left that are also needed. @code{CONFIG_MODULES} is necessary so that you can build and load modules separately and not have everything built into the kernel. @code{CONFIG_BLK_DEV_SD} is required for reading from hard drives. It is possible that there are other modules which you will need. This post does not aim to be a guide to configuring your own kernel however, so if you do decide to build a custom kernel you'll have to seek out other guides to create a kernel which is just right for your needs. The second way to setup the kernel configuration makes more use of Guix's features and allows you to share configuration segments between different kernels. For example, all machines using EFI to boot have a number of EFI configuration flags that they need. It is likely that all the kernels will share a list of file systems to support. By using variables it is easier to see at a glance what features are enabled and to make sure you don't have features in one kernel but missing in another. Left undiscussed however, is Guix's initrd and its customization. It is likely that you'll need to modify the initrd on a machine using a custom kernel, since certain modules which are expected to be built may not be available for inclusion into the initrd. @node Guix System Image API @section Guix System Image API Historically, Guix System is centered around an @code{operating-system} structure. This structure contains various fields ranging from the bootloader and kernel declaration to the services to install. Depending on the target machine, that can go from a standard @code{x86_64} machine to a small ARM single board computer such as the Pine64, the image constraints can vary a lot. The hardware manufacturers will impose different image formats with various partition sizes and offsets. To create images suitable for all those machines, a new abstraction is necessary: that's the goal of the @code{image} record. This record contains all the required information to be transformed into a standalone image, that can be directly booted on any target machine. @lisp (define-record-type* image make-image image? (name image-name ;symbol (default #f)) (format image-format) ;symbol (target image-target (default #f)) (size image-size ;size in bytes as integer (default 'guess)) (operating-system image-operating-system ; (default #f)) (partitions image-partitions ;list of (default '())) (compression? image-compression? ;boolean (default #t)) (volatile-root? image-volatile-root? ;boolean (default #t)) (substitutable? image-substitutable? ;boolean (default #t))) @end lisp This record contains the operating-system to instantiate. The @code{format} field defines the image type and can be @code{efi-raw}, @code{qcow2} or @code{iso9660} for instance. In the future, it could be extended to @code{docker} or other image types. A new directory in the Guix sources is dedicated to images definition. For now there are four files: @itemize @bullet @item @file{gnu/system/images/hurd.scm} @item @file{gnu/system/images/pine64.scm} @item @file{gnu/system/images/novena.scm} @item @file{gnu/system/images/pinebook-pro.scm} @end itemize Let's have a look to @file{pine64.scm}. It contains the @code{pine64-barebones-os} variable which is a minimal definition of an operating-system dedicated to the @b{Pine A64 LTS} board. @lisp (define pine64-barebones-os (operating-system (host-name "vignemale") (timezone "Europe/Paris") (locale "en_US.utf8") (bootloader (bootloader-configuration (bootloader u-boot-pine64-lts-bootloader) (targets '("/dev/vda")))) (initrd-modules '()) (kernel linux-libre-arm64-generic) (file-systems (cons (file-system (device (file-system-label "my-root")) (mount-point "/") (type "ext4")) %base-file-systems)) (services (cons (service agetty-service-type (agetty-configuration (extra-options '("-L")) ; no carrier detect (baud-rate "115200") (term "vt100") (tty "ttyS0"))) %base-services)))) @end lisp The @code{kernel} and @code{bootloader} fields are pointing to packages dedicated to this board. Right below, the @code{pine64-image-type} variable is also defined. @lisp (define pine64-image-type (image-type (name 'pine64-raw) (constructor (cut image-with-os arm64-disk-image <>)))) @end lisp It's using a record we haven't talked about yet, the @code{image-type} record, defined this way: @lisp (define-record-type* image-type make-image-type image-type? (name image-type-name) ;symbol (constructor image-type-constructor)) ; -> @end lisp The main purpose of this record is to associate a name to a procedure transforming an @code{operating-system} to an image. To understand why it is necessary, let's have a look to the command producing an image from an @code{operating-system} configuration file: @example guix system image my-os.scm @end example This command expects an @code{operating-system} configuration but how should we indicate that we want an image targeting a Pine64 board? We need to provide an extra information, the @code{image-type}, by passing the @code{--image-type} or @code{-t} flag, this way: @example guix system image --image-type=pine64-raw my-os.scm @end example This @code{image-type} parameter points to the @code{pine64-image-type} defined above. Hence, the @code{operating-system} declared in @code{my-os.scm} will be applied the @code{(cut image-with-os arm64-disk-image <>)} procedure to turn it into an image. The resulting image looks like: @lisp (image (format 'disk-image) (target "aarch64-linux-gnu") (operating-system my-os) (partitions (list (partition (inherit root-partition) (offset root-offset))))) @end lisp which is the aggregation of the @code{operating-system} defined in @code{my-os.scm} to the @code{arm64-disk-image} record. But enough Scheme madness. What does this image API bring to the Guix user? One can run: @example mathieu@@cervin:~$ guix system --list-image-types The available image types are: - unmatched-raw - rock64-raw - pinebook-pro-raw - pine64-raw - novena-raw - hurd-raw - hurd-qcow2 - qcow2 - iso9660 - uncompressed-iso9660 - tarball - efi-raw - mbr-raw - docker - wsl2 - raw-with-offset - efi32-raw @end example and by writing an @code{operating-system} file based on @code{pine64-barebones-os}, you can customize your image to your preferences in a file (@file{my-pine-os.scm}) like this: @lisp (use-modules (gnu services linux) (gnu system images pine64)) (let ((base-os pine64-barebones-os)) (operating-system (inherit base-os) (timezone "America/Indiana/Indianapolis") (services (cons (service earlyoom-service-type (earlyoom-configuration (prefer-regexp "icecat|chromium"))) (operating-system-user-services base-os))))) @end lisp run: @example guix system image --image-type=pine64-raw my-pine-os.scm @end example or, @example guix system image --image-type=hurd-raw my-hurd-os.scm @end example to get an image that can be written directly to a hard drive and booted from. Without changing anything to @code{my-hurd-os.scm}, calling: @example guix system image --image-type=hurd-qcow2 my-hurd-os.scm @end example will instead produce a Hurd QEMU image. @node Using security keys @section Using security keys @cindex 2FA, two-factor authentication @cindex U2F, Universal 2nd Factor @cindex security key, configuration The use of security keys can improve your security by providing a second authentication source that cannot be easily stolen or copied, at least for a remote adversary (something that you have), to the main secret (a passphrase -- something that you know), reducing the risk of impersonation. The example configuration detailed below showcases what minimal configuration needs to be made on your Guix System to allow the use of a Yubico security key. It is hoped the configuration can be useful for other security keys as well, with minor adjustments. @subsection Configuration for use as a two-factor authenticator (2FA) To be usable, the udev rules of the system should be extended with key-specific rules. The following shows how to extend your udev rules with the @file{lib/udev/rules.d/70-u2f.rules} udev rule file provided by the @code{libfido2} package from the @code{(gnu packages security-token)} module and add your user to the @samp{"plugdev"} group it uses: @lisp (use-package-modules ... security-token ...) ... (operating-system ... (users (cons* (user-account (name "your-user") (group "users") (supplementary-groups '("wheel" "netdev" "audio" "video" "plugdev")) ;<- added system group (home-directory "/home/your-user")) %base-user-accounts)) ... (services (cons* ... (udev-rules-service 'fido2 libfido2 #:groups '("plugdev"))))) @end lisp After re-configuring your system and re-logging in your graphical session so that the new group is in effect for your user, you can verify that your key is usable by launching: @example guix shell ungoogled-chromium -- chromium chrome://settings/securityKeys @end example and validating that the security key can be reset via the ``Reset your security key'' menu. If it works, congratulations, your security key is ready to be used with applications supporting two-factor authentication (2FA). @subsection Disabling OTP code generation for a Yubikey @cindex disabling yubikey OTP If you use a Yubikey security key and are irritated by the spurious OTP codes it generates when inadvertently touching the key (e.g. causing you to become a spammer in the @samp{#guix} channel when discussing from your favorite IRC client!), you can disable it via the following @command{ykman} command: @example guix shell python-yubikey-manager -- ykman config usb --force --disable OTP @end example Alternatively, you could use the @command{ykman-gui} command provided by the @code{yubikey-manager-qt} package and either wholly disable the @samp{OTP} application for the USB interface or, from the @samp{Applications -> OTP} view, delete the slot 1 configuration, which comes pre-configured with the Yubico OTP application. @subsection Requiring a Yubikey to open a KeePassXC database @cindex yubikey, keepassxc integration The KeePassXC password manager application has support for Yubikeys, but it requires installing a udev rules for your Guix System and some configuration of the Yubico OTP application on the key. The necessary udev rules file comes from the @code{yubikey-personalization} package, and can be installed like: @lisp (use-package-modules ... security-token ...) ... (operating-system ... (services (cons* ... (udev-rules-service 'yubikey yubikey-personalization)))) @end lisp After reconfiguring your system (and reconnecting your Yubikey), you'll then want to configure the OTP challenge/response application of your Yubikey on its slot 2, which is what KeePassXC uses. It's easy to do so via the Yubikey Manager graphical configuration tool, which can be invoked with: @example guix shell yubikey-manager-qt -- ykman-gui @end example First, ensure @samp{OTP} is enabled under the @samp{Interfaces} tab, then navigate to @samp{Applications -> OTP}, and click the @samp{Configure} button under the @samp{Long Touch (Slot 2)} section. Select @samp{Challenge-response}, input or generate a secret key, and click the @samp{Finish} button. If you have a second Yubikey you'd like to use as a backup, you should configure it the same way, using the @emph{same} secret key. Your Yubikey should now be detected by KeePassXC. It can be added to a database by navigating to KeePassXC's @samp{Database -> Database Security...} menu, then clicking the @samp{Add additional protection...} button, then @samp{Add Challenge-Response}, selecting the security key from the drop-down menu and clicking the @samp{OK} button to complete the setup. @node Dynamic DNS mcron job @section Dynamic DNS mcron job @cindex dynamic DNS, DDNS If your @acronym{ISP, Internet Service Provider} only provides dynamic IP addresses, it can be useful to setup a dynamic @acronym{DNS, Domain Name System} (also known as @acronym{DDNS, Dynamic DNS}) service to associate a static host name to a public but dynamic (often changing) IP address. There are multiple existing services that can be used for this; in the following mcron job, @url{https://duckdns.org, DuckDNS} is used. It should also work with other dynamic DNS services that offer a similar interface to update the IP address, such as @url{https://freedns.afraid.org/}, with minor adjustments. The mcron job is provided below, where @var{DOMAIN} should be substituted for your own domain prefix, and the DuckDNS provided token associated to @var{DOMAIN} added to the @file{/etc/duckdns/@var{DOMAIN}.token} file. @lisp (define duckdns-job ;; Update personal domain IP every 5 minutes. #~(job '(next-minute (range 0 60 5)) #$(program-file "duckdns-update" (with-extensions (list guile-gnutls) ;required by (web client) #~(begin (use-modules (ice-9 textual-ports) (web client)) (let ((token (string-trim-both (call-with-input-file "/etc/duckdns/@var{DOMAIN}.token" get-string-all))) (query-template (string-append "https://www.duckdns.org/" "update?domains=@var{DOMAIN}" "&token=~a&ip="))) (http-get (format #f query-template token)))))) "duckdns-update" #:user "nobody")) @end lisp The job then needs to be added to the list of mcron jobs for your system, using something like: @lisp (operating-system (services (cons* (service mcron-service-type (mcron-configuration (jobs (list duckdns-job ...)))) ... %base-services))) @end lisp @node Connecting to Wireguard VPN @section Connecting to Wireguard VPN To connect to a Wireguard VPN server you need the kernel module to be loaded in memory and a package providing networking tools that support it (e.g. @code{wireguard-tools} or @code{network-manager}). Here is a configuration example for Linux-Libre < 5.6, where the module is out of tree and need to be loaded manually---following revisions of the kernel have it built-in and so don't need such configuration: @lisp (use-modules (gnu)) (use-service-modules desktop) (use-package-modules vpn) (operating-system ;; … (services (cons (simple-service 'wireguard-module kernel-module-loader-service-type '("wireguard")) %desktop-services)) (packages (cons wireguard-tools %base-packages)) (kernel-loadable-modules (list wireguard-linux-compat))) @end lisp After reconfiguring and restarting your system you can either use Wireguard tools or NetworkManager to connect to a VPN server. @subsection Using Wireguard tools To test your Wireguard setup it is convenient to use @command{wg-quick}. Just give it a configuration file @command{wg-quick up ./wg0.conf}; or put that file in @file{/etc/wireguard} and run @command{wg-quick up wg0} instead. @quotation Note Be warned that the author described this command as a: “[…] very quick and dirty bash script […]”. @end quotation @subsection Using NetworkManager Thanks to NetworkManager support for Wireguard we can connect to our VPN using @command{nmcli} command. Up to this point this guide assumes that you're using Network Manager service provided by @code{%desktop-services}. Ortherwise you need to adjust your services list to load @code{network-manager-service-type} and reconfigure your Guix system. To import your VPN configuration execute nmcli import command: @example shell # nmcli connection import type wireguard file wg0.conf Connection 'wg0' (edbee261-aa5a-42db-b032-6c7757c60fde) successfully added @end example This will create a configuration file in @file{/etc/NetworkManager/wg0.nmconnection}. Next connect to the Wireguard server: @example shell $ nmcli connection up wg0 Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/6) @end example By default NetworkManager will connect automatically on system boot. To change that behaviour you need to edit your config: @example shell # nmcli connection modify wg0 connection.autoconnect no @end example For more specific information about NetworkManager and wireguard @uref{https://blogs.gnome.org/thaller/2019/03/15/wireguard-in-networkmanager/,see this post by thaller}. @node Customizing a Window Manager @section Customizing a Window Manager @cindex wm @menu * StumpWM:: * Session lock:: @end menu @node StumpWM @subsection StumpWM @cindex stumpwm You could install StumpWM with a Guix system by adding @code{stumpwm} and optionally @code{`(,stumpwm "lib")} packages to a system configuration file, e.g.@: @file{/etc/config.scm}. An example configuration can look like this: @lisp (use-modules (gnu)) (use-package-modules wm) (operating-system ;; … (packages (append (list sbcl stumpwm `(,stumpwm "lib")) %base-packages))) @end lisp @cindex stumpwm fonts By default StumpWM uses X11 fonts, which could be small or pixelated on your system. You could fix this by installing StumpWM contrib Lisp module @code{sbcl-ttf-fonts}, adding it to Guix system packages: @lisp (use-modules (gnu)) (use-package-modules fonts wm) (operating-system ;; … (packages (append (list sbcl stumpwm `(,stumpwm "lib")) sbcl-ttf-fonts font-dejavu %base-packages))) @end lisp Then you need to add the following code to a StumpWM configuration file @file{~/.stumpwm.d/init.lisp}: @lisp (require :ttf-fonts) (setf xft:*font-dirs* '("/run/current-system/profile/share/fonts/")) (setf clx-truetype:+font-cache-filename+ (concat (getenv "HOME") "/.fonts/font-cache.sexp")) (xft:cache-fonts) (set-font (make-instance 'xft:font :family "DejaVu Sans Mono" :subfamily "Book" :size 11)) @end lisp @node Session lock @subsection Session lock @cindex sessionlock Depending on your environment, locking the screen of your session might come built in or it might be something you have to set up yourself. If you use a desktop environment like GNOME or KDE, it's usually built in. If you use a plain window manager like StumpWM or EXWM, you might have to set it up yourself. @menu * Xorg:: @end menu @node Xorg @subsubsection Xorg If you use Xorg, you can use the utility @uref{https://www.mankier.com/1/xss-lock, xss-lock} to lock the screen of your session. xss-lock is triggered by DPMS which since Xorg 1.8 is auto-detected and enabled if ACPI is also enabled at kernel runtime. To use xss-lock, you can simple execute it and put it into the background before you start your window manager from e.g. your @file{~/.xsession}: @example xss-lock -- slock & exec stumpwm @end example In this example, xss-lock uses @code{slock} to do the actual locking of the screen when it determines it's appropriate, like when you suspend your device. For slock to be allowed to be a screen locker for the graphical session, it needs to be made setuid-root so it can authenticate users, and it needs a PAM service. This can be achieved by adding the following service to your @file{config.scm}: @lisp (service screen-locker-services-type (screen-locker-configuration (name "slock") (program (file-append slock "/bin/slock")))) @end lisp If you manually lock your screen, e.g. by directly calling slock when you want to lock your screen but not suspend it, it's a good idea to notify xss-lock about this so no confusion occurs. This can be done by executing @code{xset s activate} immediately before you execute slock. @node Running Guix on a Linode Server @section Running Guix on a Linode Server @cindex linode, Linode To run Guix on a server hosted by @uref{https://www.linode.com, Linode}, start with a recommended Debian server. We recommend using the default distro as a way to bootstrap Guix. Create your SSH keys. @example ssh-keygen @end example Be sure to add your SSH key for easy login to the remote server. This is trivially done via Linode's graphical interface for adding SSH keys. Go to your profile and click add SSH Key. Copy into it the output of: @example cat ~/.ssh/_rsa.pub @end example Power the Linode down. In the Linode's Storage tab, resize the Debian disk to be smaller. 30 GB free space is recommended. Then click "Add a disk", and fill out the form with the following: @itemize @bullet @item Label: "Guix" @item Filesystem: ext4 @item Set it to the remaining size @end itemize In the Configurations tab, press "Edit" on the default Debian profile. Under "Block Device Assignment" click "Add a Device". It should be @file{/dev/sdc} and you can select the "Guix" disk. Save Changes. Now "Add a Configuration", with the following: @itemize @bullet @item Label: Guix @item Kernel:GRUB 2 (it's at the bottom! This step is @b{IMPORTANT!}) @item Block device assignment: @item @file{/dev/sda}: Guix @item @file{/dev/sdb}: swap @item Root device: @file{/dev/sda} @item Turn off all the filesystem/boot helpers @end itemize Now power it back up, booting with the Debian configuration. Once it's running, ssh to your server via @code{ssh root@@@var{}}. (You can find your server IP address in your Linode Summary section.) Now you can run the "install guix from @pxref{Binary Installation,,, guix, GNU Guix}" steps: @example sudo apt-get install gpg wget https://sv.gnu.org/people/viewgpg.php?user_id=15145 -qO - | gpg --import - wget https://git.savannah.gnu.org/cgit/guix.git/plain/etc/guix-install.sh chmod +x guix-install.sh ./guix-install.sh guix pull @end example Now it's time to write out a config for the server. The key information is below. Save the resulting file as @file{guix-config.scm}. @lisp (use-modules (gnu) (guix modules)) (use-service-modules networking ssh) (use-package-modules admin certs package-management ssh tls) (operating-system (host-name "my-server") (timezone "America/New_York") (locale "en_US.UTF-8") ;; This goofy code will generate the grub.cfg ;; without installing the grub bootloader on disk. (bootloader (bootloader-configuration (bootloader (bootloader (inherit grub-bootloader) (installer #~(const #true)))))) (file-systems (cons (file-system (device "/dev/sda") (mount-point "/") (type "ext4")) %base-file-systems)) (swap-devices (list "/dev/sdb")) (initrd-modules (cons "virtio_scsi" ; Needed to find the disk %base-initrd-modules)) (users (cons (user-account (name "janedoe") (group "users") ;; Adding the account to the "wheel" group ;; makes it a sudoer. (supplementary-groups '("wheel")) (home-directory "/home/janedoe")) %base-user-accounts)) (packages (cons* nss-certs ;for HTTPS access openssh-sans-x %base-packages)) (services (cons* (service dhcp-client-service-type) (service openssh-service-type (openssh-configuration (openssh openssh-sans-x) (password-authentication? #false) (authorized-keys `(("janedoe" ,(local-file "janedoe_rsa.pub")) ("root" ,(local-file "janedoe_rsa.pub")))))) %base-services))) @end lisp Replace the following fields in the above configuration: @lisp (host-name "my-server") ; replace with your server name ; if you chose a linode server outside the U.S., then ; use tzselect to find a correct timezone string (timezone "America/New_York") ; if needed replace timezone (name "janedoe") ; replace with your username ("janedoe" ,(local-file "janedoe_rsa.pub")) ; replace with your ssh key ("root" ,(local-file "janedoe_rsa.pub")) ; replace with your ssh key @end lisp The last line in the above example lets you log into the server as root and set the initial root password (see the note at the end of this recipe about root login). After you have done this, you may delete that line from your configuration and reconfigure to prevent root login. Copy your ssh public key (eg: @file{~/.ssh/id_rsa.pub}) as @file{@var{}_rsa.pub} and put @file{guix-config.scm} in the same directory. In a new terminal run these commands. @example sftp root@@ put /path/to/files/_rsa.pub . put /path/to/files/guix-config.scm . @end example In your first terminal, mount the guix drive: @example mkdir /mnt/guix mount /dev/sdc /mnt/guix @end example Due to the way we set up the bootloader section of the guix-config.scm, only the grub configuration file will be installed. So, we need to copy over some of the other GRUB stuff already installed on the Debian system: @example mkdir -p /mnt/guix/boot/grub cp -r /boot/grub/* /mnt/guix/boot/grub/ @end example Now initialize the Guix installation: @example guix system init guix-config.scm /mnt/guix @end example Ok, power it down! Now from the Linode console, select boot and select "Guix". Once it boots, you should be able to log in via SSH! (The server config will have changed though.) You may encounter an error like: @example $ ssh root@@ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that a host key has just been changed. The fingerprint for the ECDSA key sent by the remote host is SHA256:0B+wp33w57AnKQuHCvQP0+ZdKaqYrI/kyU7CfVbS7R4. Please contact your system administrator. Add correct host key in /home/joshua/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /home/joshua/.ssh/known_hosts:3 ECDSA host key for 198.58.98.76 has changed and you have requested strict checking. Host key verification failed. @end example Either delete @file{~/.ssh/known_hosts} file, or delete the offending line starting with your server IP address. Be sure to set your password and root's password. @example ssh root@@ passwd ; for the root password passwd ; for the user password @end example You may not be able to run the above commands at this point. If you have issues remotely logging into your linode box via SSH, then you may still need to set your root and user password initially by clicking on the ``Launch Console'' option in your linode. Choose the ``Glish'' instead of ``Weblish''. Now you should be able to ssh into the machine. Hooray! At this point you can shut down the server, delete the Debian disk, and resize the Guix to the rest of the size. Congratulations! By the way, if you save it as a disk image right at this point, you'll have an easy time spinning up new Guix images! You may need to down-size the Guix image to 6144MB, to save it as an image. Then you can resize it again to the max size. @node Running Guix on a Kimsufi Server @section Running Guix on a Kimsufi Server @cindex kimsufi, Kimsufi, OVH To run Guix on a server hosted by @uref{https://www.kimsufi.com/, Kimsufi}, click on the netboot tab then select rescue64-pro and restart. OVH will email you the credentials required to ssh into a Debian system. Now you can run the "install guix from @pxref{Binary Installation,,, guix, GNU Guix}" steps: @example wget https://git.savannah.gnu.org/cgit/guix.git/plain/etc/guix-install.sh chmod +x guix-install.sh ./guix-install.sh guix pull @end example Partition the drives and format them, first stop the raid array: @example mdadm --stop /dev/md127 mdadm --zero-superblock /dev/sda2 /dev/sdb2 @end example Then wipe the disks and set up the partitions, we will create a RAID 1 array. @example wipefs -a /dev/sda wipefs -a /dev/sdb parted /dev/sda --align=opt -s -m -- mklabel gpt parted /dev/sda --align=opt -s -m -- \ mkpart bios_grub 1049kb 512MiB \ set 1 bios_grub on parted /dev/sda --align=opt -s -m -- \ mkpart primary 512MiB -512MiB set 2 raid on parted /dev/sda --align=opt -s -m -- mkpart primary linux-swap 512MiB 100% parted /dev/sdb --align=opt -s -m -- mklabel gpt parted /dev/sdb --align=opt -s -m -- \ mkpart bios_grub 1049kb 512MiB \ set 1 bios_grub on parted /dev/sdb --align=opt -s -m -- \ mkpart primary 512MiB -512MiB \ set 2 raid on parted /dev/sdb --align=opt -s -m -- mkpart primary linux-swap 512MiB 100% @end example Create the array: @example mdadm --create /dev/md127 --level=1 --raid-disks=2 \ --metadata=0.90 /dev/sda2 /dev/sdb2 @end example Now create file systems on the relevant partitions, first the boot partitions: @example mkfs.ext4 /dev/sda1 mkfs.ext4 /dev/sdb1 @end example Then the root partition: @example mkfs.ext4 /dev/md127 @end example Initialize the swap partitions: @example mkswap /dev/sda3 swapon /dev/sda3 mkswap /dev/sdb3 swapon /dev/sdb3 @end example Mount the guix drive: @example mkdir /mnt/guix mount /dev/md127 /mnt/guix @end example Now is time to write an operating system declaration @file{os.scm} file; here is a sample: @lisp (use-modules (gnu) (guix)) (use-service-modules networking ssh vpn virtualization sysctl admin mcron) (use-package-modules ssh certs tls tmux vpn virtualization) (operating-system (host-name "kimsufi") (bootloader (bootloader-configuration (bootloader grub-bootloader) (targets (list "/dev/sda" "/dev/sdb")) (terminal-outputs '(console)))) ;; Add a kernel module for RAID-1 (aka. "mirror"). (initrd-modules (cons* "raid1" %base-initrd-modules)) (mapped-devices (list (mapped-device (source (list "/dev/sda2" "/dev/sdb2")) (target "/dev/md127") (type raid-device-mapping)))) (swap-devices (list (swap-space (target "/dev/sda3")) (swap-space (target "/dev/sdb3")))) (issue ;; Default contents for /etc/issue. "\ This is the GNU system at Kimsufi. Welcome.\n") (file-systems (cons* (file-system (mount-point "/") (device "/dev/md127") (type "ext4") (dependencies mapped-devices)) %base-file-systems)) (users (cons (user-account (name "guix") (comment "guix") (group "users") (supplementary-groups '("wheel")) (home-directory "/home/guix")) %base-user-accounts)) (sudoers-file (plain-file "sudoers" "\ root ALL=(ALL) ALL %wheel ALL=(ALL) ALL guix ALL=(ALL) NOPASSWD:ALL\n")) ;; Globally-installed packages. (packages (cons* tmux nss-certs gnutls wireguard-tools %base-packages)) (services (cons* (service static-networking-service-type (list (static-networking (addresses (list (network-address (device "enp3s0") (value "@var{server-ip-address}/24")))) (routes (list (network-route (destination "default") (gateway "@var{server-gateway}")))) (name-servers '("213.186.33.99"))))) (service unattended-upgrade-service-type) (service openssh-service-type (openssh-configuration (openssh openssh-sans-x) (permit-root-login #f) (authorized-keys `(("guix" ,(plain-file "@var{ssh-key-name.pub}" "@var{ssh-public-key-content}")))))) (modify-services %base-services (sysctl-service-type config => (sysctl-configuration (settings (append '(("net.ipv6.conf.all.autoconf" . "0") ("net.ipv6.conf.all.accept_ra" . "0")) %default-sysctl-settings)))))))) @end lisp Don't forget to substitute the @var{server-ip-address}, @var{server-gateway}, @var{ssh-key-name} and @var{ssh-public-key-content} variables with your own values. The gateway is the last usable IP in your block so if you have a server with an IP of @samp{37.187.79.10} then its gateway will be @samp{37.187.79.254}. Transfer your operating system declaration @file{os.scm} file on the server via the @command{scp} or @command{sftp} commands. Now all that is left is to install Guix with a @code{guix system init} and restart. However we first need to set up a chroot, because the root partition of the rescue system is mounted on an aufs partition and if you try to install Guix it will fail at the GRUB install step complaining about the canonical path of "aufs". Install packages that will be used in the chroot: @example guix install bash-static parted util-linux-with-udev coreutils guix @end example Then run the following to create directories needed for the chroot: @example cd /mnt && \ mkdir -p bin etc gnu/store root/.guix-profile/ root/.config/guix/current \ var/guix proc sys dev @end example Copy the host resolv.conf in the chroot: @example cp /etc/resolv.conf etc/ @end example Mount block devices, the store and its database and the current guix config: @example mount --rbind /proc /mnt/proc mount --rbind /sys /mnt/sys mount --rbind /dev /mnt/dev mount --rbind /var/guix/ var/guix/ mount --rbind /gnu/store gnu/store/ mount --rbind /root/.config/ root/.config/ mount --rbind /root/.guix-profile/bin/ bin mount --rbind /root/.guix-profile root/.guix-profile/ @end example Chroot in /mnt and install the system: @example chroot /mnt/ /bin/bash guix system init /root/os.scm /guix @end example Finally, from the web user interface (UI), change @samp{netboot} to @samp{boot to disk} and restart (also from the web UI). Wait a few minutes and try to ssh with @code{ssh guix@@@var{server-ip-address>} -i @var{path-to-your-ssh-key}} You should have a Guix system up and running on Kimsufi; congratulations! @node Setting up a bind mount @section Setting up a bind mount To bind mount a file system, one must first set up some definitions before the @code{operating-system} section of the system definition. In this example we will bind mount a folder from a spinning disk drive to @file{/tmp}, to save wear and tear on the primary SSD, without dedicating an entire partition to be mounted as @file{/tmp}. First, the source drive that hosts the folder we wish to bind mount should be defined, so that the bind mount can depend on it. @lisp (define source-drive ;; "source-drive" can be named anything you want. (file-system (device (uuid "UUID goes here")) (mount-point "/path-to-spinning-disk-goes-here") (type "ext4"))) ;; Make sure to set this to the appropriate type for your drive. @end lisp The source folder must also be defined, so that guix will know it's not a regular block device, but a folder. @lisp (define (%source-directory) "/path-to-spinning-disk-goes-here/tmp") ;; "source-directory" can be named any valid variable name. @end lisp Finally, inside the @code{file-systems} definition, we must add the mount itself. @lisp (file-systems (cons* ...... source-drive ;; Must match the name you gave the source drive in the earlier definition. (file-system (device (%source-directory)) ;; Make sure "source-directory" matches your earlier definition. (mount-point "/tmp") (type "none") ;; We are mounting a folder, not a partition, so this type needs to be "none" (flags '(bind-mount)) (dependencies (list source-drive)) ;; Ensure "source-drive" matches what you've named the variable for the drive. ) ...... )) @end lisp @node Getting substitutes from Tor @section Getting substitutes from Tor Guix daemon can use a HTTP proxy to get substitutes, here we are configuring it to get them via Tor. @quotation Warning @emph{Not all} Guix daemon's traffic will go through Tor! Only HTTP/HTTPS will get proxied; FTP, Git protocol, SSH, etc connections will still go through the clearnet. Again, this configuration isn't foolproof some of your traffic won't get routed by Tor at all. Use it at your own risk. Also note that the procedure described here applies only to package substitution. When you update your guix distribution with @command{guix pull}, you still need to use @command{torsocks} if you want to route the connection to guix's git repository servers through Tor. @end quotation Guix's substitute server is available as a Onion service, if you want to use it to get your substitutes through Tor configure your system as follow: @lisp (use-modules (gnu)) (use-service-module base networking) (operating-system … (services (cons (service tor-service-type (tor-configuration (config-file (plain-file "tor-config" "HTTPTunnelPort 127.0.0.1:9250")))) (modify-services %base-services (guix-service-type config => (guix-configuration (inherit config) ;; ci.guix.gnu.org's Onion service (substitute-urls "@value{SUBSTITUTE-TOR-URL}") (http-proxy "http://localhost:9250"))))))) @end lisp This will keep a tor process running that provides a HTTP CONNECT tunnel which will be used by @command{guix-daemon}. The daemon can use other protocols than HTTP(S) to get remote resources, request using those protocols won't go through Tor since we are only setting a HTTP tunnel here. Note that @code{substitutes-urls} is using HTTPS and not HTTP or it won't work, that's a limitation of Tor's tunnel; you may want to use @command{privoxy} instead to avoid such limitations. If you don't want to always get substitutes through Tor but using it just some of the times, then skip the @code{guix-configuration}. When you want to get a substitute from the Tor tunnel run: @example sudo herd set-http-proxy guix-daemon http://localhost:9250 guix build \ --substitute-urls=@value{SUBSTITUTE-TOR-URL} @dots{} @end example @node Setting up NGINX with Lua @section Setting up NGINX with Lua @cindex nginx, lua, openresty, resty NGINX could be extended with Lua scripts. Guix provides NGINX service with ability to load Lua module and specific Lua packages, and reply to requests by evaluating Lua scripts. The following example demonstrates system definition with configuration to evaluate @file{index.lua} Lua script on HTTP request to @uref{http://localhost/hello} endpoint: @example local shell = require "resty.shell" local stdin = "" local timeout = 1000 -- ms local max_size = 4096 -- byte local ok, stdout, stderr, reason, status = shell.run([[/run/current-system/profile/bin/ls /tmp]], stdin, timeout, max_size) ngx.say(stdout) @end example @lisp (use-modules (gnu)) (use-service-modules #;… web) (use-package-modules #;… lua) (operating-system ;; … (services ;; … (service nginx-service-type (nginx-configuration (modules (list (file-append nginx-lua-module "/etc/nginx/modules/ngx_http_lua_module.so"))) (lua-package-path (list lua-resty-core lua-resty-lrucache lua-resty-signal lua-tablepool lua-resty-shell)) (lua-package-cpath (list lua-resty-signal)) (server-blocks (list (nginx-server-configuration (server-name '("localhost")) (listen '("80")) (root "/etc") (locations (list (nginx-location-configuration (uri "/hello") (body (list #~(format #f "content_by_lua_file ~s;" #$(local-file "index.lua")))))))))))))) @end lisp @node Music Server with Bluetooth Audio @section Music Server with Bluetooth Audio @cindex mpd @cindex music server, headless @cindex bluetooth, ALSA configuration MPD, the Music Player Daemon, is a flexible server-side application for playing music. Client programs on different machines on the network --- a mobile phone, a laptop, a desktop workstation --- can connect to it to control the playback of audio files from your local music collection. MPD decodes the audio files and plays them back on one or many outputs. By default MPD will play to the default audio device. In the example below we make things a little more interesting by setting up a headless music server. There will be no graphical user interface, no Pulseaudio daemon, and no local audio output. Instead we will configure MPD with two outputs: a bluetooth speaker and a web server to serve audio streams to any streaming media player. Bluetooth is often rather frustrating to set up. You will have to pair your Bluetooth device and make sure that the device is automatically connected as soon as it powers on. The Bluetooth system service returned by the @code{bluetooth-service} procedure provides the infrastructure needed to set this up. Reconfigure your system with at least the following services and packages: @lisp (operating-system ;; … (packages (cons* bluez bluez-alsa %base-packages)) (services ;; … (dbus-service #:services (list bluez-alsa)) (bluetooth-service #:auto-enable? #t))) @end lisp Start the @code{bluetooth} service and then use @command{bluetoothctl} to scan for Bluetooth devices. Try to identify your Bluetooth speaker and pick out its device ID from the resulting list of devices that is indubitably dominated by a baffling smorgasbord of your neighbors' home automation gizmos. This only needs to be done once: @example $ bluetoothctl [NEW] Controller 00:11:22:33:95:7F BlueZ 5.40 [default] [bluetooth]# power on [bluetooth]# Changing power on succeeded [bluetooth]# agent on [bluetooth]# Agent registered [bluetooth]# default-agent [bluetooth]# Default agent request successful [bluetooth]# scan on [bluetooth]# Discovery started [CHG] Controller 00:11:22:33:95:7F Discovering: yes [NEW] Device AA:BB:CC:A4:AA:CD My Bluetooth Speaker [NEW] Device 44:44:FF:2A:20:DC My Neighbor's TV @dots{} [bluetooth]# pair AA:BB:CC:A4:AA:CD Attempting to pair with AA:BB:CC:A4:AA:CD [CHG] Device AA:BB:CC:A4:AA:CD Connected: yes [My Bluetooth Speaker]# [CHG] Device AA:BB:CC:A4:AA:CD UUIDs: 0000110b-0000-1000-8000-00xxxxxxxxxx [CHG] Device AA:BB:CC:A4:AA:CD UUIDs: 0000110c-0000-1000-8000-00xxxxxxxxxx [CHG] Device AA:BB:CC:A4:AA:CD UUIDs: 0000110e-0000-1000-8000-00xxxxxxxxxx [CHG] Device AA:BB:CC:A4:AA:CD Paired: yes Pairing successful [CHG] Device AA:BB:CC:A4:AA:CD Connected: no [bluetooth]# [bluetooth]# trust AA:BB:CC:A4:AA:CD [bluetooth]# [CHG] Device AA:BB:CC:A4:AA:CD Trusted: yes Changing AA:BB:CC:A4:AA:CD trust succeeded [bluetooth]# [bluetooth]# connect AA:BB:CC:A4:AA:CD Attempting to connect to AA:BB:CC:A4:AA:CD [bluetooth]# [CHG] Device AA:BB:CC:A4:AA:CD RSSI: -63 [CHG] Device AA:BB:CC:A4:AA:CD Connected: yes Connection successful [My Bluetooth Speaker]# scan off [CHG] Device AA:BB:CC:A4:AA:CD RSSI is nil Discovery stopped [CHG] Controller 00:11:22:33:95:7F Discovering: no @end example Congratulations, you can now automatically connect to your Bluetooth speaker! It is now time to configure ALSA to use the @emph{bluealsa} Bluetooth module, so that you can define an ALSA pcm device corresponding to your Bluetooth speaker. For a headless server using @emph{bluealsa} with a fixed Bluetooth device is likely simpler than configuring Pulseaudio and its stream switching behavior. We configure ALSA by crafting a custom @code{alsa-configuration} for the @code{alsa-service-type}. The configuration will declare a @code{pcm} type @code{bluealsa} from the @code{bluealsa} module provided by the @code{bluez-alsa} package, and then define a @code{pcm} device of that type for your Bluetooth speaker. All that is left then is to make MPD send audio data to this ALSA device. We also add a secondary MPD output that makes the currently played audio files available as a stream through a web server on port 8080. When enabled a device on the network could listen to the audio stream by connecting any capable media player to the HTTP server on port 8080, independent of the status of the Bluetooth speaker. What follows is the outline of an @code{operating-system} declaration that should accomplish the above-mentioned tasks: @lisp (use-modules (gnu)) (use-service-modules audio dbus sound #;… etc) (use-package-modules audio linux #;… etc) (operating-system ;; … (packages (cons* bluez bluez-alsa %base-packages)) (services ;; … (service mpd-service-type (mpd-configuration (user "your-username") (music-dir "/path/to/your/music") (address "192.168.178.20") (outputs (list (mpd-output (type "alsa") (name "MPD") (extra-options ;; Use the same name as in the ALSA ;; configuration below. '((device . "pcm.btspeaker")))) (mpd-output (type "httpd") (name "streaming") (enabled? #false) (always-on? #true) (tags? #true) (mixer-type 'null) (extra-options '((encoder . "vorbis") (port . "8080") (bind-to-address . "192.168.178.20") (max-clients . "0") ;no limit (quality . "5.0") (format . "44100:16:1")))))))) (dbus-service #:services (list bluez-alsa)) (bluetooth-service #:auto-enable? #t) (service alsa-service-type (alsa-configuration (pulseaudio? #false) ;we don't need it (extra-options #~(string-append "\ # Declare Bluetooth audio device type \"bluealsa\" from bluealsa module pcm_type.bluealsa @{ lib \"" #$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_pcm_bluealsa.so") "\" @} # Declare control device type \"bluealsa\" from the same module ctl_type.bluealsa @{ lib \"" #$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_ctl_bluealsa.so") "\" @} # Define the actual Bluetooth audio device. pcm.btspeaker @{ type bluealsa device \"AA:BB:CC:A4:AA:CD\" # unique device identifier profile \"a2dp\" @} # Define an associated controller. ctl.btspeaker @{ type bluealsa @} ")))))) @end lisp Enjoy the music with the MPD client of your choice or a media player capable of streaming via HTTP! @c ********************************************************************* @node Containers @chapter Containers The kernel Linux provides a number of shared facilities that are available to processes in the system. These facilities include a shared view on the file system, other processes, network devices, user and group identities, and a few others. Since Linux 3.19 a user can choose to @emph{unshare} some of these shared facilities for selected processes, providing them (and their child processes) with a different view on the system. A process with an unshared @code{mount} namespace, for example, has its own view on the file system --- it will only be able to see directories that have been explicitly bound in its mount namespace. A process with its own @code{proc} namespace will consider itself to be the only process running on the system, running as PID 1. Guix uses these kernel features to provide fully isolated environments and even complete Guix System containers, lightweight virtual machines that share the host system's kernel. This feature comes in especially handy when using Guix on a foreign distribution to prevent interference from foreign libraries or configuration files that are available system-wide. @menu * Guix Containers:: Perfectly isolated environments * Guix System Containers:: A system inside your system @end menu @node Guix Containers @section Guix Containers The easiest way to get started is to use @command{guix shell} with the @option{--container} option. @xref{Invoking guix shell,,, guix, GNU Guix Reference Manual} for a reference of valid options. The following snippet spawns a minimal shell process with most namespaces unshared from the system. The current working directory is visible to the process, but anything else on the file system is unavailable. This extreme isolation can be very useful when you want to rule out any sort of interference from environment variables, globally installed libraries, or configuration files. @example guix shell --container @end example It is a bleak environment, barren, desolate. You will find that not even the GNU coreutils are available here, so to explore this deserted wasteland you need to use built-in shell commands. Even the usually gigantic @file{/gnu/store} directory is reduced to a faint shadow of itself. @example sh $ echo /gnu/store/* /gnu/store/@dots{}-gcc-10.3.0-lib /gnu/store/@dots{}-glibc-2.33 /gnu/store/@dots{}-bash-static-5.1.8 /gnu/store/@dots{}-ncurses-6.2.20210619 /gnu/store/@dots{}-bash-5.1.8 /gnu/store/@dots{}-profile /gnu/store/@dots{}-readline-8.1.1 @end example @cindex exiting a container There isn't much you can do in an environment like this other than exiting it. You can use @key{^D} or @command{exit} to terminate this limited shell environment. @cindex exposing directories, container @cindex sharing directories, container @cindex mapping locations, container You can make other directories available inside of the container environment; use @option{--expose=DIRECTORY} to bind-mount the given directory as a read-only location inside the container, or use @option{--share=DIRECTORY} to make the location writable. With an additional mapping argument after the directory name you can control the name of the directory inside the container. In the following example we map @file{/etc} on the host system to @file{/the/host/etc} inside a container in which the GNU coreutils are installed. @example sh $ guix shell --container --share=/etc=/the/host/etc coreutils $ ls /the/host/etc @end example Similarly, you can prevent the current working directory from being mapped into the container with the @option{--no-cwd} option. Another good idea is to create a dedicated directory that will serve as the container's home directory, and spawn the container shell from that directory. @cindex hide system libraries, container @cindex avoid ABI mismatch, container On a foreign system a container environment can be used to compile software that cannot possibly be linked with system libraries or with the system's compiler toolchain. A common use-case in a research context is to install packages from within an R session. Outside of a container environment there is a good chance that the foreign compiler toolchain and incompatible system libraries are found first, resulting in incompatible binaries that cannot be used by R. In a container shell this problem disappears, as system libraries and executables simply aren't available due to the unshared @code{mount} namespace. Let's take a comprehensive manifest providing a comfortable development environment for use with R: @lisp (specifications->manifest (list "r-minimal" ;; base packages "bash-minimal" "glibc-locales" "nss-certs" ;; Common command line tools lest the container is too empty. "coreutils" "grep" "which" "wget" "sed" ;; R markdown tools "pandoc" ;; Toolchain and common libraries for "install.packages" "gcc-toolchain@@10" "gfortran-toolchain" "gawk" "tar" "gzip" "unzip" "make" "cmake" "pkg-config" "cairo" "libxt" "openssl" "curl" "zlib")) @end lisp Let's use this to run R inside a container environment. For convenience we share the @code{net} namespace to use the host system's network interfaces. Now we can build R packages from source the traditional way without having to worry about ABI mismatch or incompatibilities. @example sh $ guix shell --container --network --manifest=manifest.scm -- R R version 4.2.1 (2022-06-23) -- "Funny-Looking Kid" Copyright (C) 2022 The R Foundation for Statistical Computing @dots{} > e <- Sys.getenv("GUIX_ENVIRONMENT") > Sys.setenv(GIT_SSL_CAINFO=paste0(e, "/etc/ssl/certs/ca-certificates.crt")) > Sys.setenv(SSL_CERT_FILE=paste0(e, "/etc/ssl/certs/ca-certificates.crt")) > Sys.setenv(SSL_CERT_DIR=paste0(e, "/etc/ssl/certs")) > install.packages("Cairo", lib=paste0(getwd())) @dots{} * installing *source* package 'Cairo' ... @dots{} * DONE (Cairo) The downloaded source packages are in '/tmp/RtmpCuwdwM/downloaded_packages' > library("Cairo", lib=getwd()) > # success! @end example Using container shells is fun, but they can become a little cumbersome when you want to go beyond just a single interactive process. Some tasks become a lot easier when they sit on the rock solid foundation of a proper Guix System and its rich set of system services. The next section shows you how to launch a complete Guix System inside of a container. @node Guix System Containers @section Guix System Containers The Guix System provides a wide array of interconnected system services that are configured declaratively to form a dependable stateless GNU System foundation for whatever tasks you throw at it. Even when using Guix on a foreign distribution you can benefit from the design of Guix System by running a system instance as a container. Using the same kernel features of unshared namespaces mentioned in the previous section, the resulting Guix System instance is isolated from the host system and only shares file system locations that you explicitly declare. A Guix System container differs from the shell process created by @command{guix shell --container} in a number of important ways. While in a container shell the containerized process is a Bash shell process, a Guix System container runs the Shepherd as PID 1. In a system container all system services (@pxref{Services,,, guix, GNU Guix Reference Manual}) are set up just as they would be on a Guix System in a virtual machine or on bare metal---this includes daemons managed by the GNU@tie{}Shepherd (@pxref{Shepherd Services,,, guix, GNU Guix Reference Manual}) as well as other kinds of extensions to the operating system (@pxref{Service Composition,,, guix, GNU Guix Reference Manual}). The perceived increase in complexity of running a Guix System container is easily justified when dealing with more complex applications that have higher or just more rigid requirements on their execution contexts---configuration files, dedicated user accounts, directories for caches or log files, etc. In Guix System the demands of this kind of software are satisfied through the deployment of system services. @menu * A Database Container:: * Container Networking:: @end menu @node A Database Container @subsection A Database Container A good example might be a PostgreSQL database server. Much of the complexity of setting up such a database server is encapsulated in this deceptively short service declaration: @lisp (service postgresql-service-type (postgresql-configuration (postgresql postgresql-14))) @end lisp A complete operating system declaration for use with a Guix System container would look something like this: @lisp (use-modules (gnu)) (use-package-modules databases) (use-service-modules databases) (operating-system (host-name "container") (timezone "Europe/Berlin") (file-systems (cons (file-system (device (file-system-label "does-not-matter")) (mount-point "/") (type "ext4")) %base-file-systems)) (bootloader (bootloader-configuration (bootloader grub-bootloader) (targets '("/dev/sdX")))) (services (cons* (service postgresql-service-type (postgresql-configuration (postgresql postgresql-14) (config-file (postgresql-config-file (log-destination "stderr") (hba-file (plain-file "pg_hba.conf" "\ local all all trust host all all 10.0.0.1/32 trust")) (extra-config '(("listen_addresses" "*") ("log_directory" "/var/log/postgresql"))))))) (service postgresql-role-service-type (postgresql-role-configuration (roles (list (postgresql-role (name "test") (create-database? #t)))))) %base-services))) @end lisp With @code{postgresql-role-service-type} we define a role ``test'' and create a matching database, so that we can test right away without any further manual setup. The @code{postgresql-config-file} settings allow a client from IP address 10.0.0.1 to connect without requiring authentication---a bad idea in production systems, but convenient for this example. Let's build a script that will launch an instance of this Guix System as a container. Write the @code{operating-system} declaration above to a file @file{os.scm} and then use @command{guix system container} to build the launcher. (@pxref{Invoking guix system,,, guix, GNU Guix Reference Manual}). @example $ guix system container os.scm The following derivations will be built: /gnu/store/@dots{}-run-container.drv @dots{} building /gnu/store/@dots{}-run-container.drv... /gnu/store/@dots{}-run-container @end example Now that we have a launcher script we can run it to spawn the new system with a running PostgreSQL service. Note that due to some as yet unresolved limitations we need to run the launcher as the root user, for example with @command{sudo}. @example $ sudo /gnu/store/@dots{}-run-container system container is running as PID 5983 @dots{} @end example Background the process with @key{Ctrl-z} followed by @command{bg}. Note the process ID in the output; we will need it to connect to the container later. You know what? Let's try attaching to the container right now. We will use @command{nsenter}, a tool provided by the @code{util-linux} package: @example $ guix shell util-linux $ sudo nsenter -a -t 5983 root@@container /# pgrep -a postgres 49 /gnu/store/@dots{}-postgresql-14.4/bin/postgres -D /var/lib/postgresql/data --config-file=/gnu/store/@dots{}-postgresql.conf -p 5432 51 postgres: checkpointer 52 postgres: background writer 53 postgres: walwriter 54 postgres: autovacuum launcher 55 postgres: stats collector 56 postgres: logical replication launcher root@@container /# exit @end example The PostgreSQL service is running in the container! @node Container Networking @subsection Container Networking @cindex container networking What good is a Guix System running a PostgreSQL database service as a container when we can only talk to it with processes originating in the container? It would be much better if we could talk to the database over the network. The easiest way to do this is to create a pair of connected virtual Ethernet devices (known as @code{veth}). We move one of the devices (@code{ceth-test}) into the @code{net} namespace of the container and leave the other end (@code{veth-test}) of the connection on the host system. @example pid=5983 ns="guix-test" host="veth-test" client="ceth-test" # Attach the new net namespace "guix-test" to the container PID. sudo ip netns attach $ns $pid # Create the pair of devices sudo ip link add $host type veth peer name $client # Move the client device into the container's net namespace sudo ip link set $client netns $ns @end example Then we configure the host side: @example sudo ip link set $host up sudo ip addr add 10.0.0.1/24 dev $host @end example @dots{}and then we configure the client side: @example sudo ip netns exec $ns ip link set lo up sudo ip netns exec $ns ip link set $client up sudo ip netns exec $ns ip addr add 10.0.0.2/24 dev $client @end example At this point the host can reach the container at IP address 10.0.0.2, and the container can reach the host at IP 10.0.0.1. This is all we need to talk to the database server inside the container from the host system on the outside. @example $ psql -h 10.0.0.2 -U test psql (14.4) Type "help" for help. test=> CREATE TABLE hello (who TEXT NOT NULL); CREATE TABLE test=> INSERT INTO hello (who) VALUES ('world'); INSERT 0 1 test=> SELECT * FROM hello; who ------- world (1 row) @end example Now that we're done with this little demonstration let's clean up: @example sudo kill $pid sudo ip netns del $ns sudo ip link del $host @end example @c ********************************************************************* @node Virtual Machines @chapter Virtual Machines Guix can produce disk images (@pxref{Invoking guix system,,, guix, GNU Guix Reference Manual}) that can be used with virtual machines solutions such as virt-manager, GNOME Boxes or the more bare QEMU, among others. This chapter aims to provide hands-on, practical examples that relates to the usage and configuration of virtual machines on a Guix System. @menu * Network bridge for QEMU:: * Routed network for libvirt:: @end menu @node Network bridge for QEMU @section Network bridge for QEMU @cindex Network bridge interface @cindex networking, bridge @cindex qemu, network bridge By default, QEMU uses a so-called ``user mode'' host network back-end, which is convenient as it does not require any configuration. Unfortunately, it is also quite limited. In this mode, the guest @abbr{VM, virtual machine} can access the network the same way the host would, but it cannot be reached from the host. Additionally, since the QEMU user networking mode relies on ICMP, ICMP-based networking tools such as @command{ping} do @emph{not} work in this mode. Thus, it is often desirable to configure a network bridge, which enables the guest to fully participate in the network. This is necessary, for example, when the guest is to be used as a server. @subsection Creating a network bridge interface There are many ways to create a network bridge. The following command shows how to use NetworkManager and its @command{nmcli} command line interface (CLI) tool, which should already be available if your operating system declaration is based on one of the desktop templates: @example sh # nmcli con add type bridge con-name br0 ifname br0 @end example To have this bridge be part of your network, you must associate your network bridge with the Ethernet interface used to connect with the network. Assuming your interface is named @samp{enp2s0}, the following command can be used to do so: @example sh # nmcli con add type bridge-slave ifname enp2s0 master br0 @end example @quotation Important Only Ethernet interfaces can be added to a bridge. For wireless interfaces, consider the routed network approach detailed in @xref{Routed network for libvirt}. @end quotation By default, the network bridge will allow your guests to obtain their IP address via DHCP, if available on your local network. For simplicity, this is what we will use here. To easily find the guests, they can be configured to advertise their host names via mDNS. @subsection Configuring the QEMU bridge helper script QEMU comes with a helper program to conveniently make use of a network bridge interface as an unprivileged user @pxref{Network options,,, QEMU, QEMU Documentation}. The binary must be made setuid root for proper operation; this can be achieved by adding it to the @code{setuid-programs} field of your (host) @code{operating-system} definition, as shown below: @example lisp (setuid-programs (cons (file-append qemu "/libexec/qemu-bridge-helper") %setuid-programs)) @end example The file @file{/etc/qemu/bridge.conf} must also be made to allow the bridge interface, as the default is to deny all. Add the following to your list of services to do so: @example lisp (extra-special-file "/etc/qemu/host.conf" "allow br0\n") @end example @subsection Invoking QEMU with the right command line options When invoking QEMU, the following options should be provided so that the network bridge is used, after having selected a unique MAC address for the guest. @quotation Important By default, a single MAC address is used for all guests, unless provided. Failing to provided different MAC addresses to each virtual machine making use of the bridge would cause networking issues. @end quotation @example sh $ qemu-system-x86_64 [...] \ -device virtio-net-pci,netdev=user0,mac=XX:XX:XX:XX:XX:XX \ -netdev bridge,id=user0,br=br0 \ [...] @end example To generate MAC addresses that have the QEMU registered prefix, the following snippet can be employed: @example sh mac_address="52:54:00:$(dd if=/dev/urandom bs=512 count=1 2>/dev/null \ | md5sum \ | sed -E 's/^(..)(..)(..).*$/\1:\2:\3/')" echo $mac_address @end example @subsection Networking issues caused by Docker If you use Docker on your machine, you may experience connectivity issues when attempting to use a network bridge, which are caused by Docker also relying on network bridges and configuring its own routing rules. The solution is add the following @code{iptables} snippet to your @code{operating-system} declaration: @example lisp (service iptables-service-type (iptables-configuration (ipv4-rules (plain-file "iptables.rules" "\ *filter :INPUT ACCEPT [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] -A FORWARD -i br0 -o br0 -j ACCEPT COMMIT ")) @end example @node Routed network for libvirt @section Routed network for libvirt @cindex Virtual network bridge interface @cindex networking, virtual bridge @cindex libvirt, virtual network bridge If the machine hosting your virtual machines is connected wirelessly to the network, you won't be able to use a true network bridge as explained in the preceding section (@pxref{Network bridge for QEMU}). In this case, the next best option is to use a @emph{virtual} bridge with static routing and to configure a libvirt-powered virtual machine to use it (via the @command{virt-manager} GUI for example). This is similar to the default mode of operation of QEMU/libvirt, except that instead of using @abbr{NAT, Network Address Translation}, it relies on static routes to join the @abbr{VM, virtual machine} IP address to the @abbr{LAN, local area network}. This provides two-way connectivity to and from the virtual machine, which is needed for exposing services hosted on the virtual machine. @subsection Creating a virtual network bridge A virtual network bridge consists of a few components/configurations, such as a @abbr{TUN, network tunnel} interface, DHCP server (dnsmasq) and firewall rules (iptables). The @command{virsh} command, provided by the @code{libvirt} package, makes it very easy to create a virtual bridge. You first need to choose a network subnet for your virtual bridge; if your home LAN is in the @samp{192.168.1.0/24} network, you could opt to use e.g.@: @samp{192.168.2.0/24}. Define an XML file, e.g.@: @file{/tmp/virbr0.xml}, containing the following: @example virbr0 @end example Then create and configure the interface using the @command{virsh} command, as root: @example virsh net-define /tmp/virbr0.xml virsh net-autostart virbr0 virsh net-start virbr0 @end example The @samp{virbr0} interface should now be visible e.g.@: via the @samp{ip address} command. It will be automatically started every time your libvirt virtual machine is started. @subsection Configuring the static routes for your virtual bridge If you configured your virtual machine to use your newly created @samp{virbr0} virtual bridge interface, it should already receive an IP via DHCP such as @samp{192.168.2.15} and be reachable from the server hosting it, e.g.@: via @samp{ping 192.168.2.15}. There's one last configuration needed so that the VM can reach the external network: adding static routes to the network's router. In this example, the LAN network is @samp{192.168.1.0/24} and the router configuration web page may be accessible via e.g.@: the @url{http://192.168.1.1} page. On a router running the @url{https://librecmc.org/, libreCMC} firmware, you would navigate to the @clicksequence{Network @click{} Static Routes} page (@url{https://192.168.1.1/cgi-bin/luci/admin/network/routes}), and you would add a new entry to the @samp{Static IPv4 Routes} with the following information: @table @samp @item Interface lan @item Target 192.168.2.0 @item IPv4-Netmask 255.255.255.0 @item IPv4-Gateway @var{server-ip} @item Route type unicast @end table where @var{server-ip} is the IP address of the machine hosting the VMs, which should be static. After saving/applying this new static route, external connectivity should work from within your VM; you can e.g.@: run @samp{ping gnu.org} to verify that it functions correctly. @c ********************************************************************* @node Advanced package management @chapter Advanced package management Guix is a functional package manager that offers many features beyond what more traditional package managers can do. To the uninitiated, those features might not have obvious use cases at first. The purpose of this chapter is to demonstrate some advanced package management concepts. @pxref{Package Management,,, guix, GNU Guix Reference Manual} for a complete reference. @menu * Guix Profiles in Practice:: Strategies for multiple profiles and manifests. @end menu @node Guix Profiles in Practice @section Guix Profiles in Practice Guix provides a very useful feature that may be quite foreign to newcomers: @dfn{profiles}. They are a way to group package installations together and all users on the same system are free to use as many profiles as they want. Whether you're a developer or not, you may find that multiple profiles bring you great power and flexibility. While they shift the paradigm somewhat compared to @emph{traditional package managers}, they are very convenient to use once you've understood how to set them up. @quotation Note This section is an opinionated guide on the use of multiple profiles. It predates @command{guix shell} and its fast profile cache (@pxref{Invoking guix shell,,, guix, GNU Guix Reference Manual}). In many cases, you may find that using @command{guix shell} to set up the environment you need, when you need it, is less work that maintaining a dedicated profile. Your call! @end quotation If you are familiar with Python's @samp{virtualenv}, you can think of a profile as a kind of universal @samp{virtualenv} that can hold any kind of software whatsoever, not just Python software. Furthermore, profiles are self-sufficient: they capture all the runtime dependencies which guarantees that all programs within a profile will always work at any point in time. Multiple profiles have many benefits: @itemize @item Clean semantic separation of the various packages a user needs for different contexts. @item Multiple profiles can be made available into the environment either on login or within a dedicated shell. @item Profiles can be loaded on demand. For instance, the user can use multiple shells, each of them running different profiles. @item Isolation: Programs from one profile will not use programs from the other, and the user can even install different versions of the same programs to the two profiles without conflict. @item Deduplication: Profiles share dependencies that happens to be the exact same. This makes multiple profiles storage-efficient. @item Reproducible: when used with declarative manifests, a profile can be fully specified by the Guix commit that was active when it was set up. This means that the exact same profile can be @uref{https://guix.gnu.org/blog/2018/multi-dimensional-transactions-and-rollbacks-oh-my/, set up anywhere and anytime}, with just the commit information. See the section on @ref{Reproducible profiles}. @item Easier upgrades and maintenance: Multiple profiles make it easy to keep package listings at hand and make upgrades completely frictionless. @end itemize Concretely, here follows some typical profiles: @itemize @item The dependencies of a project you are working on. @item Your favourite programming language libraries. @item Laptop-specific programs (like @samp{powertop}) that you don't need on a desktop. @item @TeX{}live (this one can be really useful when you need to install just one package for this one document you've just received over email). @item Games. @end itemize Let's dive in the set up! @menu * Basic setup with manifests:: * Required packages:: * Default profile:: * The benefits of manifests:: * Reproducible profiles:: @end menu @node Basic setup with manifests @subsection Basic setup with manifests A Guix profile can be set up @i{via} a @dfn{manifest}. A manifest is a snippet of Scheme code that specifies the set of packages you want to have in your profile; it looks like this: @lisp (specifications->manifest '("package-1" ;; Version 1.3 of package-2. "package-2@@1.3" ;; The "lib" output of package-3. "package-3:lib" ; ... "package-N")) @end lisp @xref{Writing Manifests,,, guix, GNU Guix Reference Manual}, for more information about the syntax. We can create a manifest specification per profile and install them this way: @example GUIX_EXTRA_PROFILES=$HOME/.guix-extra-profiles mkdir -p "$GUIX_EXTRA_PROFILES"/my-project # if it does not exist yet guix package --manifest=/path/to/guix-my-project-manifest.scm --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project @end example Here we set an arbitrary variable @samp{GUIX_EXTRA_PROFILES} to point to the directory where we will store our profiles in the rest of this article. Placing all your profiles in a single directory, with each profile getting its own sub-directory, is somewhat cleaner. This way, each sub-directory will contain all the symlinks for precisely one profile. Besides, ``looping over profiles'' becomes obvious from any programming language (e.g.@: a shell script) by simply looping over the sub-directories of @samp{$GUIX_EXTRA_PROFILES}. Note that it's also possible to loop over the output of @example guix package --list-profiles @end example although you'll probably have to filter out @file{~/.config/guix/current}. To enable all profiles on login, add this to your @file{~/.bash_profile} (or similar): @example for i in $GUIX_EXTRA_PROFILES/*; do profile=$i/$(basename "$i") if [ -f "$profile"/etc/profile ]; then GUIX_PROFILE="$profile" . "$GUIX_PROFILE"/etc/profile fi unset profile done @end example Note to Guix System users: the above reflects how your default profile @file{~/.guix-profile} is activated from @file{/etc/profile}, that latter being loaded by @file{~/.bashrc} by default. You can obviously choose to only enable a subset of them: @example for i in "$GUIX_EXTRA_PROFILES"/my-project-1 "$GUIX_EXTRA_PROFILES"/my-project-2; do profile=$i/$(basename "$i") if [ -f "$profile"/etc/profile ]; then GUIX_PROFILE="$profile" . "$GUIX_PROFILE"/etc/profile fi unset profile done @end example When a profile is off, it's straightforward to enable it for an individual shell without "polluting" the rest of the user session: @example GUIX_PROFILE="path/to/my-project" ; . "$GUIX_PROFILE"/etc/profile @end example The key to enabling a profile is to @emph{source} its @samp{etc/profile} file. This file contains shell code that exports the right environment variables necessary to activate the software contained in the profile. It is built automatically by Guix and meant to be sourced. It contains the same variables you would get if you ran: @example guix package --search-paths=prefix --profile=$my_profile" @end example Once again, see (@pxref{Invoking guix package,,, guix, GNU Guix Reference Manual}) for the command line options. To upgrade a profile, simply install the manifest again: @example guix package -m /path/to/guix-my-project-manifest.scm -p "$GUIX_EXTRA_PROFILES"/my-project/my-project @end example To upgrade all profiles, it's easy enough to loop over them. For instance, assuming your manifest specifications are stored in @file{~/.guix-manifests/guix-$profile-manifest.scm}, with @samp{$profile} being the name of the profile (e.g.@: "project1"), you could do the following in Bourne shell: @example for profile in "$GUIX_EXTRA_PROFILES"/*; do guix package --profile="$profile" --manifest="$HOME/.guix-manifests/guix-$profile-manifest.scm" done @end example Each profile has its own generations: @example guix package -p "$GUIX_EXTRA_PROFILES"/my-project/my-project --list-generations @end example You can roll-back to any generation of a given profile: @example guix package -p "$GUIX_EXTRA_PROFILES"/my-project/my-project --switch-generations=17 @end example Finally, if you want to switch to a profile without inheriting from the current environment, you can activate it from an empty shell: @example env -i $(which bash) --login --noprofile --norc . my-project/etc/profile @end example @node Required packages @subsection Required packages Activating a profile essentially boils down to exporting a bunch of environmental variables. This is the role of the @samp{etc/profile} within the profile. @emph{Note: Only the environmental variables of the packages that consume them will be set.} For instance, @samp{MANPATH} won't be set if there is no consumer application for man pages within the profile. So if you need to transparently access man pages once the profile is loaded, you've got two options: @itemize @item Either export the variable manually, e.g. @example export MANPATH=/path/to/profile$@{MANPATH:+:@}$MANPATH @end example @item Or include @samp{man-db} to the profile manifest. @end itemize The same is true for @samp{INFOPATH} (you can install @samp{info-reader}), @samp{PKG_CONFIG_PATH} (install @samp{pkg-config}), etc. @node Default profile @subsection Default profile What about the default profile that Guix keeps in @file{~/.guix-profile}? You can assign it the role you want. Typically you would install the manifest of the packages you want to use all the time. Alternatively, you could keep it ``manifest-less'' for throw-away packages that you would just use for a couple of days. This way makes it convenient to run @example guix install package-foo guix upgrade package-bar @end example without having to specify the path to a profile. @node The benefits of manifests @subsection The benefits of manifests Manifests let you @dfn{declare} the set of packages you'd like to have in a profile (@pxref{Writing Manifests,,, guix, GNU Guix Reference Manual}). They are a convenient way to keep your package lists around and, say, to synchronize them across multiple machines using a version control system. A common complaint about manifests is that they can be slow to install when they contain large number of packages. This is especially cumbersome when you just want get an upgrade for one package within a big manifest. This is one more reason to use multiple profiles, which happen to be just perfect to break down manifests into multiple sets of semantically connected packages. Using multiple, small profiles provides more flexibility and usability. Manifests come with multiple benefits. In particular, they ease maintenance: @itemize @item When a profile is set up from a manifest, the manifest itself is self-sufficient to keep a ``package listing'' around and reinstall the profile later or on a different system. For ad-hoc profiles, we would need to generate a manifest specification manually and maintain the package versions for the packages that don't use the default version. @item @code{guix package --upgrade} always tries to update the packages that have propagated inputs, even if there is nothing to do. Guix manifests remove this problem. @item When partially upgrading a profile, conflicts may arise (due to diverging dependencies between the updated and the non-updated packages) and they can be annoying to resolve manually. Manifests remove this problem altogether since all packages are always upgraded at once. @item As mentioned above, manifests allow for reproducible profiles, while the imperative @code{guix install}, @code{guix upgrade}, etc. do not, since they produce different profiles every time even when they hold the same packages. See @uref{https://issues.guix.gnu.org/issue/33285, the related discussion on the matter}. @item Manifest specifications are usable by other @samp{guix} commands. For example, you can run @code{guix weather -m manifest.scm} to see how many substitutes are available, which can help you decide whether you want to try upgrading today or wait a while. Another example: you can run @code{guix pack -m manifest.scm} to create a pack containing all the packages in the manifest (and their transitive references). @item Finally, manifests have a Scheme representation, the @samp{} record type. They can be manipulated in Scheme and passed to the various Guix @uref{https://en.wikipedia.org/wiki/Api, APIs}. @end itemize It's important to understand that while manifests can be used to declare profiles, they are not strictly equivalent: profiles have the side effect that they ``pin'' packages in the store, which prevents them from being garbage-collected (@pxref{Invoking guix gc,,, guix, GNU Guix Reference Manual}) and ensures that they will still be available at any point in the future. The @command{guix shell} command also protects recently-used profiles from garbage collection; profiles that have not been used for a while may be garbage-collected though, along with the packages they refer to. To be 100% sure that a given profile will never be collected, install the manifest to a profile and use @code{GUIX_PROFILE=/the/profile; . "$GUIX_PROFILE"/etc/profile} as explained above: this guarantees that our hacking environment will be available at all times. @emph{Security warning:} While keeping old profiles around can be convenient, keep in mind that outdated packages may not have received the latest security fixes. @node Reproducible profiles @subsection Reproducible profiles To reproduce a profile bit-for-bit, we need two pieces of information: @itemize @item a manifest (@pxref{Writing Manifests,,, guix, GNU Guix Reference Manual}); @item a Guix channel specification (@pxref{Replicating Guix,,, guix, GNU Guix Reference Manual}). @end itemize Indeed, manifests alone might not be enough: different Guix versions (or different channels) can produce different outputs for a given manifest. You can output the Guix channel specification with @samp{guix describe --format=channels} (@pxref{Invoking guix describe,,, guix, GNU Guix Reference Manual}). Save this to a file, say @samp{channel-specs.scm}. On another computer, you can use the channel specification file and the manifest to reproduce the exact same profile: @example GUIX_EXTRA_PROFILES=$HOME/.guix-extra-profiles GUIX_EXTRA=$HOME/.guix-extra mkdir -p "$GUIX_EXTRA"/my-project guix pull --channels=channel-specs.scm --profile="$GUIX_EXTRA/my-project/guix" mkdir -p "$GUIX_EXTRA_PROFILES/my-project" "$GUIX_EXTRA"/my-project/guix/bin/guix package --manifest=/path/to/guix-my-project-manifest.scm --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project @end example It's safe to delete the Guix channel profile you've just installed with the channel specification, the project profile does not depend on it. @node Software Development @chapter Software Development @cindex development, with Guix @cindex software development, with Guix Guix is a handy tool for developers; @command{guix shell}, in particular, gives a standalone development environment for your package, no matter what language(s) it's written in (@pxref{Invoking guix shell,,, guix, GNU Guix Reference Manual}). To benefit from it, you have to initially write a package definition and have it either in Guix proper, or in a channel, or directly in your project's source tree as a @file{guix.scm} file. This last option is appealing: all developers have to do to get set up is clone the project's repository and run @command{guix shell}, with no arguments. Development needs go beyond development environments though. How can developers perform continuous integration of their code in Guix build environments? How can they deliver their code straight to adventurous users? This chapter describes a set of files developers can add to their repository to set up Guix-based development environments, continuous integration, and continuous delivery---all at once@footnote{This chapter is adapted from a @uref{https://guix.gnu.org/en/blog/2023/from-development-environments-to-continuous-integrationthe-ultimate-guide-to-software-development-with-guix/, blog post} published in June 2023 on the Guix web site.}. @menu * Getting Started:: Step 0: using `guix shell'. * Building with Guix:: Step 1: building your code. * The Repository as a Channel:: Step 2: turning the repo in a channel. * Package Variants:: Bonus: Defining variants. * Setting Up Continuous Integration:: Step 3: continuous integration. * Build Manifest:: Bonus: Manifest. * Wrapping Up:: Recap. @end menu @node Getting Started @section Getting Started How do we go about ``Guixifying'' a repository? The first step, as we've seen, will be to add a @file{guix.scm} at the root of the repository in question. We'll take @uref{https://www.gnu.org/software/guile,Guile} as an example in this chapter: it's written in Scheme (mostly) and C, and has a number of dependencies---a C compilation tool chain, C libraries, Autoconf and its friends, LaTeX, and so on. The resulting @file{guix.scm} looks like the usual package definition (@pxref{Defining Packages,,, guix, GNU Guix Reference Manual}), just without the @code{define-public} bit: @lisp ;; The ‘guix.scm’ file for Guile, for use by ‘guix shell’. (use-modules (guix) (guix build-system gnu) ((guix licenses) #:prefix license:) (gnu packages autotools) (gnu packages base) (gnu packages bash) (gnu packages bdw-gc) (gnu packages compression) (gnu packages flex) (gnu packages gdb) (gnu packages gettext) (gnu packages gperf) (gnu packages libffi) (gnu packages libunistring) (gnu packages linux) (gnu packages pkg-config) (gnu packages readline) (gnu packages tex) (gnu packages texinfo) (gnu packages version-control)) (package (name "guile") (version "3.0.99-git") ;funky version number (source #f) ;no source (build-system gnu-build-system) (native-inputs (append (list autoconf automake libtool gnu-gettext flex texinfo texlive-base ;for "make pdf" texlive-epsf gperf git gdb strace readline lzip pkg-config) ;; When cross-compiling, a native version of Guile itself is ;; needed. (if (%current-target-system) (list this-package) '()))) (inputs (list libffi bash-minimal)) (propagated-inputs (list libunistring libgc)) (native-search-paths (list (search-path-specification (variable "GUILE_LOAD_PATH") (files '("share/guile/site/3.0"))) (search-path-specification (variable "GUILE_LOAD_COMPILED_PATH") (files '("lib/guile/3.0/site-ccache"))))) (synopsis "Scheme implementation intended especially for extensions") (description "Guile is the GNU Ubiquitous Intelligent Language for Extensions, and it's actually a full-blown Scheme implementation!") (home-page "https://www.gnu.org/software/guile/") (license license:lgpl3+)) @end lisp Quite a bit of boilerplate, but now someone who'd like to hack on Guile now only needs to run: @lisp guix shell @end lisp That gives them a shell containing all the dependencies of Guile: those listed above, but also @emph{implicit dependencies} such as the GCC tool chain, GNU@ Make, sed, grep, and so on. @xref{Invoking guix shell,,, guix, GNU Guix Reference Manual}, for more info on @command{guix shell}. @quotation The chef's recommendation Our suggestion is to create development environments like this: @example guix shell --container --link-profile @end example @noindent ... or, for short: @example guix shell -CP @end example That gives a shell in an isolated container, and all the dependencies show up in @code{$HOME/.guix-profile}, which plays well with caches such as @file{config.cache} (@pxref{Cache Files,,, autoconf, Autoconf}) and absolute file names recorded in generated @code{Makefile}s and the likes. The fact that the shell runs in a container brings peace of mind: nothing but the current directory and Guile's dependencies is visible inside the container; nothing from the system can possibly interfere with your development. @end quotation @node Building with Guix @section Level 1: Building with Guix Now that we have a package definition (@pxref{Getting Started}), why not also take advantage of it so we can build Guile with Guix? We had left the @code{source} field empty, because @command{guix shell} above only cares about the @emph{inputs} of our package---so it can set up the development environment---not about the package itself. To build the package with Guix, we'll need to fill out the @code{source} field, along these lines: @lisp (use-modules (guix) (guix git-download) ;for ‘git-predicate’ @dots{}) (define vcs-file? ;; Return true if the given file is under version control. (or (git-predicate (current-source-directory)) (const #t))) ;not in a Git checkout (package (name "guile") (version "3.0.99-git") ;funky version number (source (local-file "." "guile-checkout" #:recursive? #t #:select? vcs-file?)) @dots{}) @end lisp Here's what we changed compared to the previous section: @enumerate @item We added @code{(guix git-download)} to our set of imported modules, so we can use its @code{git-predicate} procedure. @item We defined @code{vcs-file?} as a procedure that returns true when passed a file that is under version control. For good measure, we add a fallback case for when we're not in a Git checkout: always return true. @item We set @code{source} to a @uref{https://guix.gnu.org/manual/devel/en/html_node/G_002dExpressions.html#index-local_002dfile,@code{local-file}}---a recursive copy of the current directory (@code{"."}), limited to files under version control (the @code{#:select?} bit). @end enumerate From there on, our @file{guix.scm} file serves a second purpose: it lets us build the software with Guix. The whole point of building with Guix is that it's a ``clean'' build---you can be sure nothing from your working tree or system interferes with the build result---and it lets you test a variety of things. First, you can do a plain native build: @example guix build -f guix.scm @end example But you can also build for another system (possibly after setting up @pxref{Daemon Offload Setup, offloading,, guix, GNU Guix Reference Manual} or @pxref{Virtualization Services, transparent emulation,, guix, GNU Guix Reference Manual}): @lisp guix build -f guix.scm -s aarch64-linux -s riscv64-linux @end lisp @noindent @dots{} or cross-compile: @lisp guix build -f guix.scm --target=x86_64-w64-mingw32 @end lisp You can also use @dfn{package transformations} to test package variants (@pxref{Package Transformation Options,,, guix, GNU Guix Reference Manual}): @example # What if we built with Clang instead of GCC? guix build -f guix.scm \ --with-c-toolchain=guile@@3.0.99-git=clang-toolchain # What about that under-tested configure flag? guix build -f guix.scm \ --with-configure-flag=guile@@3.0.99-git=--disable-networking @end example Handy! @node The Repository as a Channel @section Level 2: The Repository as a Channel We now have a Git repository containing (among other things) a package definition (@pxref{Building with Guix}). Can't we turn it into a @dfn{channel} (@pxref{Channels,,, guix, GNU Guix Reference Manual})? After all, channels are designed to ship package definitions to users, and that's exactly what we're doing with our @file{guix.scm}. Turns out we can indeed turn it into a channel, but with one caveat: we must create a separate directory for the @code{.scm} file(s) of our channel so that @command{guix pull} doesn't load unrelated @code{.scm} files when someone pulls the channel---and in Guile, there are lots of them! So we'll start like this, keeping a top-level @file{guix.scm} symlink for the sake of @command{guix shell}: @lisp mkdir -p .guix/modules mv guix.scm .guix/modules/guile-package.scm ln -s .guix/modules/guile-package.scm guix.scm @end lisp To make it usable as part of a channel, we need to turn our @file{guix.scm} file into a @dfn{package module} (@pxref{Package Modules,,, guix, GNU Guix Reference Manual}): we do that by changing the @code{use-modules} form at the top to a @code{define-module} form. We also need to actually @emph{export} a package variable, with @code{define-public}, while still returning the package value at the end of the file so we can still use @command{guix shell} and @command{guix build -f guix.scm}. The end result looks like this (not repeating things that haven't changed): @lisp (define-module (guile-package) #:use-module (guix) #:use-module (guix git-download) ;for ‘git-predicate’ @dots{}) (define vcs-file? ;; Return true if the given file is under version control. (or (git-predicate (dirname (dirname (current-source-directory)))) (const #t))) ;not in a Git checkout (define-public guile (package (name "guile") (version "3.0.99-git") ;funky version number (source (local-file "../.." "guile-checkout" #:recursive? #t #:select? vcs-file?)) @dots{})) ;; Return the package object define above at the end of the module. guile @end lisp We need one last thing: a @uref{https://guix.gnu.org/manual/devel/en/html_node/Package-Modules-in-a-Sub_002ddirectory.html,@code{.guix-channel} file} so Guix knows where to look for package modules in our repository: @lisp ;; This file lets us present this repo as a Guix channel. (channel (version 0) (directory ".guix/modules")) ;look for package modules under .guix/modules/ @end lisp To recap, we now have these files: @lisp . ├── .guix-channel ├── guix.scm → .guix/modules/guile-package.scm └── .guix     └── modules        └── guile-package.scm @end lisp And that's it: we have a channel! (We could do better and support @uref{https://guix.gnu.org/manual/devel/en/html_node/Specifying-Channel-Authorizations.html,@emph{channel authentication}} so users know they're pulling genuine code. We'll spare you the details here but it's worth considering!) Users can pull from this channel by @uref{https://guix.gnu.org/manual/devel/en/html_node/Specifying-Additional-Channels.html,adding it to @code{~/.config/guix/channels.scm}}, along these lines: @lisp (append (list (channel (name 'guile) (url "https://git.savannah.gnu.org/git/guile.git") (branch "main"))) %default-channels) @end lisp After running @command{guix pull}, we can see the new package: @example $ guix describe Generation 264 May 26 2023 16:00:35 (current) guile 36fd2b4 repository URL: https://git.savannah.gnu.org/git/guile.git branch: main commit: 36fd2b4920ae926c79b936c29e739e71a6dff2bc guix c5bc698 repository URL: https://git.savannah.gnu.org/git/guix.git commit: c5bc698e8922d78ed85989985cc2ceb034de2f23 $ guix package -A ^guile$ guile 3.0.99-git out,debug guile-package.scm:51:4 guile 3.0.9 out,debug gnu/packages/guile.scm:317:2 guile 2.2.7 out,debug gnu/packages/guile.scm:258:2 guile 2.2.4 out,debug gnu/packages/guile.scm:304:2 guile 2.0.14 out,debug gnu/packages/guile.scm:148:2 guile 1.8.8 out gnu/packages/guile.scm:77:2 $ guix build guile@@3.0.99-git [@dots{}] /gnu/store/axnzbl89yz7ld78bmx72vpqp802dwsar-guile-3.0.99-git-debug /gnu/store/r34gsij7f0glg2fbakcmmk0zn4v62s5w-guile-3.0.99-git @end example That's how, as a developer, you get your software delivered directly into the hands of users! No intermediaries, yet no loss of transparency and provenance tracking. With that in place, it also becomes trivial for anyone to create Docker images, Deb/RPM packages, or a plain tarball with @command{guix pack} (@pxref{Invoking guix pack,,, guix, GNU Guix Reference Manual}): @example # How about a Docker image of our Guile snapshot? guix pack -f docker -S /bin=bin guile@@3.0.99-git # And a relocatable RPM? guix pack -f rpm -R -S /bin=bin guile@@3.0.99-git @end example @node Package Variants @section Bonus: Package Variants We now have an actual channel, but it contains only one package (@pxref{The Repository as a Channel}). While we're at it, we can define @dfn{package variants} (@pxref{Defining Package Variants,,, guix, GNU Guix Reference Manual}) in our @file{guile-package.scm} file, variants that we want to be able to test as Guile developers---similar to what we did above with transformation options. We can add them like so: @lisp ;; This is the ‘.guix/modules/guile-package.scm’ file. (define-module (guile-package) @dots{}) (define-public guile @dots{}) (define (package-with-configure-flags p flags) "Return P with FLAGS as additional 'configure' flags." (package/inherit p (arguments (substitute-keyword-arguments (package-arguments p) ((#:configure-flags original-flags #~(list)) #~(append #$original-flags #$flags)))))) (define-public guile-without-threads (package (inherit (package-with-configure-flags guile #~(list "--without-threads"))) (name "guile-without-threads"))) (define-public guile-without-networking (package (inherit (package-with-configure-flags guile #~(list "--disable-networking"))) (name "guile-without-networking"))) ;; Return the package object defined above at the end of the module. guile @end lisp We can build these variants as regular packages once we've pulled the channel. Alternatively, from a checkout of Guile, we can run a command like this one from the top level: @lisp guix build -L $PWD/.guix/modules guile-without-threads @end lisp @node Setting Up Continuous Integration @section Level 3: Setting Up Continuous Integration @cindex continuous integration (CI) The channel we defined above (@pxref{The Repository as a Channel}) becomes even more interesting once we set up @uref{https://en.wikipedia.org/wiki/Continuous_integration, @dfn{continuous integration}} (CI). There are several ways to do that. You can use one of the mainstream continuous integration tools, such as GitLab-CI. To do that, you need to make sure you run jobs in a Docker image or virtual machine that has Guix installed. If we were to do that in the case of Guile, we'd have a job that runs a shell command like this one: @lisp guix build -L $PWD/.guix/modules guile@@3.0.99-git @end lisp Doing this works great and has the advantage of being easy to achieve on your favorite CI platform. That said, you'll really get the most of it by using @uref{https://guix.gnu.org/en/cuirass,Cuirass}, a CI tool designed for and tightly integrated with Guix. Using it is more work than using a hosted CI tool because you first need to set it up, but that setup phase is greatly simplified if you use its Guix System service (@pxref{Continuous Integration,,, guix, GNU Guix Reference Manual}). Going back to our example, we give Cuirass a spec file that goes like this: @lisp ;; Cuirass spec file to build all the packages of the ‘guile’ channel. (list (specification (name "guile") (build '(channels guile)) (channels (append (list (channel (name 'guile) (url "https://git.savannah.gnu.org/git/guile.git") (branch "main"))) %default-channels)))) @end lisp It differs from what you'd do with other CI tools in two important ways: @itemize @item Cuirass knows it's tracking @emph{two} channels, @code{guile} and @code{guix}. Indeed, our own @code{guile} package depends on many packages provided by the @code{guix} channel---GCC, the GNU libc, libffi, and so on. Changes to packages from the @code{guix} channel can potentially influence our @code{guile} build and this is something we'd like to see as soon as possible as Guile developers. @item Build results are not thrown away: they can be distributed as @dfn{substitutes} so that users of our @code{guile} channel transparently get pre-built binaries! (@pxref{Substitutes,,, guix, GNU Guix Reference Manual}, for background info on substitutes.) @end itemize From a developer's viewpoint, the end result is this @uref{https://ci.guix.gnu.org/jobset/guile,status page} listing @emph{evaluations}: each evaluation is a combination of commits of the @code{guix} and @code{guile} channels providing a number of @emph{jobs}---one job per package defined in @file{guile-package.scm} times the number of target architectures. As for substitutes, they come for free! As an example, since our @code{guile} jobset is built on ci.guix.gnu.org, which runs @command{guix publish} (@pxref{Invoking guix publish,,, guix, GNU Guix Reference Manual}) in addition to Cuirass, one automatically gets substitutes for @code{guile} builds from ci.guix.gnu.org; no additional work is needed for that. @node Build Manifest @section Bonus: Build manifest The Cuirass spec above is convenient: it builds every package in our channel, which includes a few variants (@pxref{Setting Up Continuous Integration}). However, this might be insufficiently expressive in some cases: one might want specific cross-compilation jobs, transformations, Docker images, RPM/Deb packages, or even system tests. To achieve that, you can write a @dfn{manifest} (@pxref{Writing Manifests,,, guix, GNU Guix Reference Manual}). The one we have for Guile has entries for the package variants we defined above, as well as additional variants and cross builds: @lisp ;; This is ‘.guix/manifest.scm’. (use-modules (guix) (guix profiles) (guile-package)) ;import our own package module (define* (package->manifest-entry* package system #:key target) "Return a manifest entry for PACKAGE on SYSTEM, optionally cross-compiled to TARGET." (manifest-entry (inherit (package->manifest-entry package)) (name (string-append (package-name package) "." system (if target (string-append "." target) ""))) (item (with-parameters ((%current-system system) (%current-target-system target)) package)))) (define native-builds (manifest (append (map (lambda (system) (package->manifest-entry* guile system)) '("x86_64-linux" "i686-linux" "aarch64-linux" "armhf-linux" "powerpc64le-linux")) (map (lambda (guile) (package->manifest-entry* guile "x86_64-linux")) (cons (package (inherit (package-with-c-toolchain guile `(("clang-toolchain" ,(specification->package "clang-toolchain"))))) (name "guile-clang")) (list guile-without-threads guile-without-networking guile-debug guile-strict-typing)))))) (define cross-builds (manifest (map (lambda (target) (package->manifest-entry* guile "x86_64-linux" #:target target)) '("i586-pc-gnu" "aarch64-linux-gnu" "riscv64-linux-gnu" "i686-w64-mingw32" "x86_64-linux-gnu")))) (concatenate-manifests (list native-builds cross-builds)) @end lisp We won't go into the details of this manifest; suffice to say that it provides additional flexibility. We now need to tell Cuirass to build this manifest, which is done with a spec slightly different from the previous one: @lisp ;; Cuirass spec file to build all the packages of the ‘guile’ channel. (list (specification (name "guile") (build '(manifest ".guix/manifest.scm")) (channels (append (list (channel (name 'guile) (url "https://git.savannah.gnu.org/git/guile.git") (branch "main"))) %default-channels)))) @end lisp We changed the @code{(build @dots{})} part of the spec to @code{'(manifest ".guix/manifest.scm")} so that it would pick our manifest, and that's it! @node Wrapping Up @section Wrapping Up We picked Guile as the running example in this chapter and you can see the result here: @itemize @item @uref{https://git.savannah.gnu.org/cgit/guile.git/tree/.guix-channel?id=cd57379b3df636198d8cd8e76c1bfbc523762e79,@code{.guix-channel}}; @item @uref{https://git.savannah.gnu.org/cgit/guile.git/tree/.guix/modules/guile-package.scm?id=cd57379b3df636198d8cd8e76c1bfbc523762e79,@code{.guix/modules/guile-package.scm}} with the top-level @file{guix.scm} symlink; @item @uref{https://git.savannah.gnu.org/cgit/guile.git/tree/.guix/manifest.scm?id=cd57379b3df636198d8cd8e76c1bfbc523762e79,@code{.guix/manifest.scm}}. @end itemize These days, repositories are commonly peppered with dot files for various tools: @code{.envrc}, @code{.gitlab-ci.yml}, @code{.github/workflows}, @code{Dockerfile}, @code{.buildpacks}, @code{Aptfile}, @code{requirements.txt}, and whatnot. It may sound like we're proposing a bunch of @emph{additional} files, but in fact those files are expressive enough to @emph{supersede} most or all of those listed above. With a couple of files, we get support for: @itemize @item development environments (@command{guix shell}); @item pristine test builds, including for package variants and for cross-compilation (@command{guix build}); @item continuous integration (with Cuirass or with some other tool); @item continuous delivery to users (@emph{via} the channel and with pre-built binaries); @item generation of derivative build artifacts such as Docker images or Deb/RPM packages (@command{guix pack}). @end itemize This a nice (in our view!) unified tool set for reproducible software deployment, and an illustration of how you as a developer can benefit from it! @c ********************************************************************* @node Environment management @chapter Environment management Guix provides multiple tools to manage environment. This chapter demonstrate such utilities. @menu * Guix environment via direnv:: Setup Guix environment with direnv @end menu @node Guix environment via direnv @section Guix environment via direnv Guix provides a @samp{direnv} package, which could extend shell after directory change. This tool could be used to prepare a pure Guix environment. The following example provides a shell function for @file{~/.direnvrc} file, which could be used from Guix Git repository in @file{~/src/guix/.envrc} file to setup a build environment similar to described in @pxref{Building from Git,,, guix, GNU Guix Reference Manual}. Create a @file{~/.direnvrc} with a Bash code: @example # Thanks export_function() @{ local name=$1 local alias_dir=$PWD/.direnv/aliases mkdir -p "$alias_dir" PATH_add "$alias_dir" local target="$alias_dir/$name" if declare -f "$name" >/dev/null; then echo "#!$SHELL" > "$target" declare -f "$name" >> "$target" 2>/dev/null # Notice that we add shell variables to the function trigger. echo "$name \$*" >> "$target" chmod +x "$target" fi @} use_guix() @{ # Set GitHub token. export GUIX_GITHUB_TOKEN="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" # Unset 'GUIX_PACKAGE_PATH'. export GUIX_PACKAGE_PATH="" # Recreate a garbage collector root. gcroots="$HOME/.config/guix/gcroots" mkdir -p "$gcroots" gcroot="$gcroots/guix" if [ -L "$gcroot" ] then rm -v "$gcroot" fi # Miscellaneous packages. PACKAGES_MAINTENANCE=( direnv git git:send-email git-cal gnupg guile-colorized guile-readline less ncurses openssh xdot ) # Environment packages. PACKAGES=(help2man guile-sqlite3 guile-gcrypt) # Thanks eval "$(guix environment --search-paths --root="$gcroot" --pure guix --ad-hoc $@{PACKAGES[@@]@} $@{PACKAGES_MAINTENANCE[@@]@} "$@@")" # Predefine configure flags. configure() @{ ./configure --localstatedir=/var --prefix= @} export_function configure # Run make and optionally build something. build() @{ make -j 2 if [ $# -gt 0 ] then ./pre-inst-env guix build "$@@" fi @} export_function build # Predefine push Git command. push() @{ git push --set-upstream origin @} export_function push clear # Clean up the screen. git-cal --author='Your Name' # Show contributions calendar. # Show commands help. echo " build build a package or just a project if no argument provided configure run ./configure with predefined parameters push push to upstream Git repository " @} @end example Every project containing @file{.envrc} with a string @code{use guix} will have predefined environment variables and procedures. Run @command{direnv allow} to setup the environment for the first time. @c ********************************************************************* @node Installing Guix on a Cluster @chapter Installing Guix on a Cluster @cindex cluster installation @cindex high-performance computing, HPC @cindex HPC, high-performance computing Guix is appealing to scientists and @acronym{HPC, high-performance computing} practitioners: it makes it easy to deploy potentially complex software stacks, and it lets you do so in a reproducible fashion---you can redeploy the exact same software on different machines and at different points in time. In this chapter we look at how a cluster sysadmin can install Guix for system-wide use, such that it can be used on all the cluster nodes, and discuss the various tradeoffs@footnote{This chapter is adapted from a @uref{https://hpc.guix.info/blog/2017/11/installing-guix-on-a-cluster/, blog post published on the Guix-HPC web site in 2017}.}. @quotation Note Here we assume that the cluster is running a GNU/Linux distro other than Guix System and that we are going to install Guix on top of it. @end quotation @menu * Setting Up a Head Node:: The node that runs the daemon. * Setting Up Compute Nodes:: Client nodes. * Cluster Network Access:: Dealing with network access restrictions. * Cluster Disk Usage:: Disk usage considerations. * Cluster Security Considerations:: Keeping the cluster secure. @end menu @node Setting Up a Head Node @section Setting Up a Head Node The recommended approach is to set up one @emph{head node} running @command{guix-daemon} and exporting @file{/gnu/store} over NFS to compute nodes. Remember that @command{guix-daemon} is responsible for spawning build processes and downloads on behalf of clients (@pxref{Invoking guix-daemon,,, guix, GNU Guix Reference Manual}), and more generally accessing @file{/gnu/store}, which contains all the package binaries built by all the users (@pxref{The Store,,, guix, GNU Guix Reference Manual}). ``Client'' here refers to all the Guix commands that users see, such as @code{guix install}. On a cluster, these commands may be running on the compute nodes and we'll want them to talk to the head node's @code{guix-daemon} instance. To begin with, the head node can be installed following the usual binary installation instructions (@pxref{Binary Installation,,, guix, GNU Guix Reference Manual}). Thanks to the installation script, this should be quick. Once installation is complete, we need to make some adjustments. Since we want @code{guix-daemon} to be reachable not just from the head node but also from the compute nodes, we need to arrange so that it listens for connections over TCP/IP. To do that, we'll edit the systemd startup file for @command{guix-daemon}, @file{/etc/systemd/system/guix-daemon.service}, and add a @code{--listen} argument to the @code{ExecStart} line so that it looks something like this: @example ExecStart=/var/guix/profiles/per-user/root/current-guix/bin/guix-daemon --build-users-group=guixbuild --listen=/var/guix/daemon-socket/socket --listen=0.0.0.0 @end example For these changes to take effect, the service needs to be restarted: @example systemctl daemon-reload systemctl restart guix-daemon @end example @quotation Note The @code{--listen=0.0.0.0} bit means that @code{guix-daemon} will process @emph{all} incoming TCP connections on port 44146 (@pxref{Invoking guix-daemon,,, guix, GNU Guix Reference Manual}). This is usually fine in a cluster setup where the head node is reachable exclusively from the cluster's local area network---you don't want that to be exposed to the Internet! @end quotation The next step is to define our NFS exports in @uref{https://linux.die.net/man/5/exports,@file{/etc/exports}} by adding something along these lines: @example /gnu/store *(ro) /var/guix *(rw, async) /var/log/guix *(ro) @end example The @file{/gnu/store} directory can be exported read-only since only @command{guix-daemon} on the master node will ever modify it. @file{/var/guix} contains @emph{user profiles} as managed by @code{guix package}; thus, to allow users to install packages with @code{guix package}, this must be read-write. Users can create as many profiles as they like in addition to the default profile, @file{~/.guix-profile}. For instance, @code{guix package -p ~/dev/python-dev -i python} installs Python in a profile reachable from the @code{~/dev/python-dev} symlink. To make sure that this profile is protected from garbage collection---i.e., that Python will not be removed from @file{/gnu/store} while this profile exists---, @emph{home directories should be mounted on the head node} as well so that @code{guix-daemon} knows about these non-standard profiles and avoids collecting software they refer to. It may be a good idea to periodically remove unused bits from @file{/gnu/store} by running @command{guix gc} (@pxref{Invoking guix gc,,, guix, GNU Guix Reference Manual}). This can be done by adding a crontab entry on the head node: @example root@@master# crontab -e @end example @noindent ... with something like this: @example # Every day at 5AM, run the garbage collector to make sure # at least 10 GB are free on /gnu/store. 0 5 * * 1 /usr/local/bin/guix gc -F10G @end example We're done with the head node! Let's look at compute nodes now. @node Setting Up Compute Nodes @section Setting Up Compute Nodes First of all, we need compute nodes to mount those NFS directories that the head node exports. This can be done by adding the following lines to @uref{https://linux.die.net/man/5/fstab,@file{/etc/fstab}}: @example @var{head-node}:/gnu/store /gnu/store nfs defaults,_netdev,vers=3 0 0 @var{head-node}:/var/guix /var/guix nfs defaults,_netdev,vers=3 0 0 @var{head-node}:/var/log/guix /var/log/guix nfs defaults,_netdev,vers=3 0 0 @end example @noindent ... where @var{head-node} is the name or IP address of your head node. From there on, assuming the mount points exist, you should be able to mount each of these on the compute nodes. Next, we need to provide a default @command{guix} command that users can run when they first connect to the cluster (eventually they will invoke @command{guix pull}, which will provide them with their ``own'' @command{guix} command). Similar to what the binary installation script did on the head node, we'll store that in @file{/usr/local/bin}: @example mkdir -p /usr/local/bin ln -s /var/guix/profiles/per-user/root/current-guix/bin/guix \ /usr/local/bin/guix @end example We then need to tell @code{guix} to talk to the daemon running on our master node, by adding these lines to @code{/etc/profile}: @example GUIX_DAEMON_SOCKET="guix://@var{head-node}" export GUIX_DAEMON_SOCKET @end example To avoid warnings and make sure @code{guix} uses the right locale, we need to tell it to use locale data provided by Guix (@pxref{Application Setup,,, guix, GNU Guix Reference Manual}): @example GUIX_LOCPATH=/var/guix/profiles/per-user/root/guix-profile/lib/locale export GUIX_LOCPATH # Here we must use a valid locale name. Try "ls $GUIX_LOCPATH/*" # to see what names can be used. LC_ALL=fr_FR.utf8 export LC_ALL @end example For convenience, @code{guix package} automatically generates @file{~/.guix-profile/etc/profile}, which defines all the environment variables necessary to use the packages---@code{PATH}, @code{C_INCLUDE_PATH}, @code{PYTHONPATH}, etc. Thus it's a good idea to source it from @code{/etc/profile}: @example GUIX_PROFILE="$HOME/.guix-profile" if [ -f "$GUIX_PROFILE/etc/profile" ]; then . "$GUIX_PROFILE/etc/profile" fi @end example Last but not least, Guix provides command-line completion notably for Bash and zsh. In @code{/etc/bashrc}, consider adding this line: @verbatim . /var/guix/profiles/per-user/root/current-guix/etc/bash_completion.d/guix @end verbatim Voilà! You can check that everything's in place by logging in on a compute node and running: @example guix install hello @end example The daemon on the head node should download pre-built binaries on your behalf and unpack them in @file{/gnu/store}, and @command{guix install} should create @file{~/.guix-profile} containing the @file{~/.guix-profile/bin/hello} command. @node Cluster Network Access @section Network Access Guix requires network access to download source code and pre-built binaries. The good news is that only the head node needs that since compute nodes simply delegate to it. It is customary for cluster nodes to have access at best to a @emph{white list} of hosts. Our head node needs at least @code{ci.guix.gnu.org} in this white list since this is where it gets pre-built binaries from by default, for all the packages that are in Guix proper. Incidentally, @code{ci.guix.gnu.org} also serves as a @emph{content-addressed mirror} of the source code of those packages. Consequently, it is sufficient to have @emph{only} @code{ci.guix.gnu.org} in that white list. Software packages maintained in a separate repository such as one of the various @uref{https://hpc.guix.info/channels, HPC channels} are of course unavailable from @code{ci.guix.gnu.org}. For these packages, you may want to extend the white list such that source and pre-built binaries (assuming this-party servers provide binaries for these packages) can be downloaded. As a last resort, users can always download source on their workstation and add it to the cluster's @file{/gnu/store}, like this: @verbatim GUIX_DAEMON_SOCKET=ssh://compute-node.example.org \ guix download http://starpu.gforge.inria.fr/files/starpu-1.2.3/starpu-1.2.3.tar.gz @end verbatim The above command downloads @code{starpu-1.2.3.tar.gz} @emph{and} sends it to the cluster's @code{guix-daemon} instance over SSH. Air-gapped clusters require more work. At the moment, our suggestion would be to download all the necessary source code on a workstation running Guix. For instance, using the @option{--sources} option of @command{guix build} (@pxref{Invoking guix build,,, guix, GNU Guix Reference Manual}), the example below downloads all the source code the @code{openmpi} package depends on: @example $ guix build --sources=transitive openmpi @dots{} /gnu/store/xc17sm60fb8nxadc4qy0c7rqph499z8s-openmpi-1.10.7.tar.bz2 /gnu/store/s67jx92lpipy2nfj5cz818xv430n4b7w-gcc-5.4.0.tar.xz /gnu/store/npw9qh8a46lrxiwh9xwk0wpi3jlzmjnh-gmp-6.0.0a.tar.xz /gnu/store/hcz0f4wkdbsvsdky3c0vdvcawhdkyldb-mpfr-3.1.5.tar.xz /gnu/store/y9akh452n3p4w2v631nj0injx7y0d68x-mpc-1.0.3.tar.gz /gnu/store/6g5c35q8avfnzs3v14dzl54cmrvddjm2-glibc-2.25.tar.xz /gnu/store/p9k48dk3dvvk7gads7fk30xc2pxsd66z-hwloc-1.11.8.tar.bz2 /gnu/store/cry9lqidwfrfmgl0x389cs3syr15p13q-gcc-5.4.0.tar.xz /gnu/store/7ak0v3rzpqm2c5q1mp3v7cj0rxz0qakf-libfabric-1.4.1.tar.bz2 /gnu/store/vh8syjrsilnbfcf582qhmvpg1v3rampf-rdma-core-14.tar.gz … @end example (In case you're wondering, that's more than 320@ MiB of @emph{compressed} source code.) We can then make a big archive containing all of this (@pxref{Invoking guix archive,,, guix, GNU Guix Reference Manual}): @verbatim $ guix archive --export \ `guix build --sources=transitive openmpi` \ > openmpi-source-code.nar @end verbatim @dots{} and we can eventually transfer that archive to the cluster on removable storage and unpack it there: @verbatim $ guix archive --import < openmpi-source-code.nar @end verbatim This process has to be repeated every time new source code needs to be brought to the cluster. As we write this, the research institutes involved in Guix-HPC do not have air-gapped clusters though. If you have experience with such setups, we would like to hear feedback and suggestions. @node Cluster Disk Usage @section Disk Usage @cindex disk usage, on a cluster A common concern of sysadmins' is whether this is all going to eat a lot of disk space. If anything, if something is going to exhaust disk space, it's going to be scientific data sets rather than compiled software---that's our experience with almost ten years of Guix usage on HPC clusters. Nevertheless, it's worth taking a look at how Guix contributes to disk usage. First, having several versions or variants of a given package in @file{/gnu/store} does not necessarily cost much, because @command{guix-daemon} implements deduplication of identical files, and package variants are likely to have a number of common files. As mentioned above, we recommend having a cron job to run @code{guix gc} periodically, which removes @emph{unused} software from @file{/gnu/store}. However, there's always a possibility that users will keep lots of software in their profiles, or lots of old generations of their profiles, which is ``live'' and cannot be deleted from the viewpoint of @command{guix gc}. The solution to this is for users to regularly remove old generations of their profile. For instance, the following command removes generations that are more than two-month old: @example guix package --delete-generations=2m @end example Likewise, it's a good idea to invite users to regularly upgrade their profile, which can reduce the number of variants of a given piece of software stored in @file{/gnu/store}: @example guix pull guix upgrade @end example As a last resort, it is always possible for sysadmins to do some of this on behalf of their users. Nevertheless, one of the strengths of Guix is the freedom and control users get on their software environment, so we strongly recommend leaving users in control. @node Cluster Security Considerations @section Security Considerations @cindex security, on a cluster On an HPC cluster, Guix is typically used to manage scientific software. Security-critical software such as the operating system kernel and system services such as @code{sshd} and the batch scheduler remain under control of sysadmins. The Guix project has a good track record delivering security updates in a timely fashion (@pxref{Security Updates,,, guix, GNU Guix Reference Manual}). To get security updates, users have to run @code{guix pull && guix upgrade}. Because Guix uniquely identifies software variants, it is easy to see if a vulnerable piece of software is in use. For instance, to check whether the glibc@ 2.25 variant without the mitigation patch against ``@uref{https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt,Stack Clash}'', one can check whether user profiles refer to it at all: @example guix gc --referrers /gnu/store/…-glibc-2.25 @end example This will report whether profiles exist that refer to this specific glibc variant. @c ********************************************************************* @node Acknowledgments @chapter Acknowledgments Guix is based on the @uref{https://nixos.org/nix/, Nix package manager}, which was designed and implemented by Eelco Dolstra, with contributions from other people (see the @file{nix/AUTHORS} file in Guix.) Nix pioneered functional package management, and promoted unprecedented features, such as transactional package upgrades and rollbacks, per-user profiles, and referentially transparent build processes. Without this work, Guix would not exist. The Nix-based software distributions, Nixpkgs and NixOS, have also been an inspiration for Guix. GNU@tie{}Guix itself is a collective work with contributions from a number of people. See the @file{AUTHORS} file in Guix for more information on these fine people. The @file{THANKS} file lists people who have helped by reporting bugs, taking care of the infrastructure, providing artwork and themes, making suggestions, and more---thank you! This document includes adapted sections from articles that have previously been published on the Guix blog at @uref{https://guix.gnu.org/blog} and on the Guix-HPC blog at @uref{https://hpc.guix.info/blog}. @c ********************************************************************* @node GNU Free Documentation License @appendix GNU Free Documentation License @cindex license, GNU Free Documentation License @include fdl-1.3.texi @c ********************************************************************* @node Concept Index @unnumbered Concept Index @printindex cp @bye @c Local Variables: @c ispell-local-dictionary: "american"; @c End: