gnu: system: Add Linux container module.

* gnu/system/linux-container.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* gnu/system.scm: Export 'operating-system-etc-directory',
  'operating-system-boot-script', 'operating-system-locale-directory', and
  'file-union'.
  (operating-system-boot-script): Add #:container? keyword argument.
  (operating-system-activation-script): Add #:container?  keyword argument.
  Don't call 'activate-firmware' or 'activate-ptrace-attach' when activating a
  container.

Revert "PRELIMINARY: Add three programs to %setuid-programs."

This reverts commit fb1e06fc5f7648ab3078876f009fa7a983b17c41.

PRELIMINARY: Add three programs to %setuid-programs.

system: Default to newest linux-libre.

* gnu/system.scm (<operating-system>)[kernel]: Change default to
  LINUX-LIBRE.

system: Add 'ping6' to %SETUID-PROGRAMS.

* gnu/system.scm (%setuid-programs): Add 'ping6'.

system: Default to Linux-libre 4.0.

* gnu/system.scm (<operating-system>)[kernel]: Change default to
  LINUX-LIBRE-4.0.

Merge branch 'master' into core-updates

file-systems: Add a 'dependencies' field to <file-system>.

* gnu/system/file-systems.scm (<file-system>)[dependencies]: New field.
* gnu/system.scm (other-file-system-services)[requirements]: Honor
  'file-system-dependencies'.
* doc/guix.texi (File Systems): Document it.

system: Add 'kernel-arguments' field.

* gnu/system.scm (<operating-system>)[kernel-arguments]: New field.
  (operating-system-grub.cfg): Honor it.
  (operating-system-parameters-file): Add 'kernel-arguments' to the parameters
  file.
* guix/scripts/system.scm (previous-grub-entries)[system->grub-entry]: Read
  the 'kernel-arguments' field of the parameters file, when available.
* gnu/system/vm.scm (system-qemu-image/shared-store-script):
  Use (operating-system-kernel-arguments os) in '-append'.
* doc/guix.texi (operating-system Reference): Document it.

build: file-systems: Import (guix build syscalls) for non-static Guiles.

* gnu/build/file-systems.scm: Import (guix build syscalls) when 'mount' is not
  defined.
* gnu/system.scm (operating-system-activation-script): Include (guix build
  syscalls) module in derivation.

system: Fix typo.

* gnu/system.scm (etc-directory): Fix typo in a comment.

system: emacs-site-file: Use 'geiser-install to load geiser.

Suggested by Alex Kost <alezost@gmail.com>.

* gnu/system.scm (emacs-site-file): Use 'geiser-install to load geiser
  instead of setting 'geiser-guile-load-path' manually.

Merge branch 'master' into core-updates

system: Rename 'sudoers' into 'sudoers-file'.

* gnu/system.scm (<operating-system>): Rename record field.
  (etc-directory): Rename argument.
  (operating-system-etc-directory): Adjust accordingly.
* doc/guix.texi (operating-system Reference): Likewise.

Merge branch 'master' into core-updates

system: 'hosts-file' is now a file-like object.

Partly fixes <http://bugs.gnu.org/20720>.
Reported by Alex Kost <alezost@gmail.com>.

* gnu/system.scm (default-/etc/hosts): Change 'text-file' to 'plain-file'.
  (maybe-file->monadic): New procedure.
  (operating-system-etc-directory): Use it.
* doc/guix.texi (operating-system Reference, Networking Services): Adjust
  accordingly.

system: 'sudoers' is now a file-like object.

Partly fixes <http://bugs.gnu.org/20720>
Reported by Alex Kost <alezost@gmail.com>.

* gnu/system.scm (etc-directory): Change default #:sudoers value to a
  'plain-file'.  Don't bind it.  Remove #~#$.
  (maybe-string->file): New procedure.
  (operating-system-etc-directory): Use it.
  (%sudoers-specification): Use 'plain-file'.
* doc/guix.texi (operating-system Reference): Adjust accordingly.

system: Define '%base-user-accounts'.

* gnu/system/shadow.scm (%base-user-accounts): New variable.
* gnu/system.scm (<operating-system>)[users]: Use it as the default value.
* gnu/system/examples/bare-bones.tmpl (users): Use it.
* gnu/system/examples/desktop.tmpl (users): Likewise.
* doc/guix.texi (operating-system Reference, User Accounts): Adjust
  accordingly.

system: Make sure user accounts refer to existing groups.

Fixes <http://bugs.gnu.org/20646>.
Reported by David Thompson <davet@gnu.org>.

* gnu/system/shadow.scm (assert-valid-users/groups): New procedure
* gnu/system.scm (operating-system-activation-script): Use it.
* tests/guix-system.sh (make_user_config): New function.
  Add 3 tests using it.
* po/guix/POTFILES.in: Add gnu/system/shadow.scm.

Merge branch 'master' into gtk-rebuild

Conflicts:
	gnu/packages/gtk.scm