machine: Allow non-root users to deploy.

* doc/guix.texi (Invoking guix deploy): Add section describing
prerequisites for deploying as a non-root user.
* guix/remote.scm (remote-pipe-for-gexp): New optional 'become-command'
argument.
(%remote-eval): New optional 'become-command' argument.
(remote-eval): New 'become-command' keyword argument.
* guix/ssh.scm (remote-inferior): New optional 'become-command'
argument.
(inferior-remote-eval): New optional 'become-command' argument.
(remote-authorize-signing-key): New optional 'become-command' argument.
* gnu/machine/ssh.scm (machine-become-command): New variable.
(managed-host-remote-eval): Invoke 'remote-eval' with the
'#:become-command' keyword.
(deploy-managed-host): Invoke 'remote-authorize-signing-key' with the
'#:become-command' keyword.

1 files changed, 8 insertions, 0 deletions

diff --git a/gnu/machine/ssh.scm b/gnu/machine/ssh.scm
index 670990a633..fb15d39e61 100644
--- a/gnu/machine/ssh.scm
+++ b/gnu/machine/ssh.scm
@@ -101,6 +101,14 @@ one from the configuration's parameters if one was not provided."
 ;;; Remote evaluation.
 ;;;
 
+(define (machine-become-command machine)
+  "Return as a list of strings the program and arguments necessary to run a
+shell command with escalated privileges for MACHINE's configuration."
+  (if (string= "root" (machine-ssh-configuration-user
+                       (machine-configuration machine)))
+      '()
+      '("/run/setuid-programs/sudo" "-n" "--")))
+
 (define (managed-host-remote-eval machine exp)
   "Internal implementation of 'machine-remote-eval' for MACHINE instances with
 an environment type of 'managed-host."