system: Add /etc/subuid and /etc/subgid support.

This commit adds a Guix System service to handle allocation of subuid
and subgid requests.  Users that don't care can just add themselves as a
subid-range and don't need to specify anything but their user name.
Users that care about specific ranges, such as possibly LXD, can specify
a start and a count.

* doc/guix.texi (Miscellaneous Services): Document it.
* gnu/build/activation.scm (activate-subuids+subgids): New variable.
* gnu/local.mk: Add gnu/tests/shadow.scm.
* gnu/system/accounts.scm (sexp->subid-range): New variable.
* gnu/system/shadow.scm (%root-subid): New variable;
(subids-configuration): new record;
(subid-range->gexp): new variable;
(assert-valid-subids): new variable;
(delete-duplicate-ranges): new variable;
(subids-activation): new variable;
(subids-extension): new record;
(append-subid-ranges): new variable;
(subids-extension-merge): new variable;
(subids-service-type): new variable.
* gnu/tests/shadow.scm (subids): New system test.

Change-Id: I3755e1c75771220c74fe8ae5de1a7d90f2376635
Signed-off-by: Giacomo Leidi <goodoldpaul@autistici.org>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

0 files changed, 0 insertions, 0 deletions