system: Use (guix profiles) to build the system profile.

* gnu/system.scm (union): Remove.
  (operating-system-profile): Use 'profile-derivation' and related
  procedures instead of 'union'.

system: Add the 'system?' field for user groups.

Suggested by Mark H. Weaver.

* gnu/system/shadow.scm (<user-group>)[system?]: New field.
  (%base-groups): Introduce 'system-group' macro, and use it.
* gnu/system.scm (user-group->gexp): Pass the 'system?' field.
* guix/build/activation.scm (add-group): Add #:system? and honor it.
  (activate-users+groups): Handle the 'system?' field.
* gnu/system/file-systems.scm (%tty-gid): Choose an ID below 1000.
* doc/guix.texi (User Accounts): Document the 'system?' field.

system: Recognize more file system flags.

* guix/build/linux-initrd.scm (MS_NOSUID, MS_NODEV, MS_NOEXEC): New
  variables.
  (mount-flags->bit-mask): New procedure.
  (mount-file-system)[flags->bit-mask]: Remove.
  Use 'mount-flags->bit-mask' instead.
  In /etc/mtab, use the empty string when OPTIONS is false.
* gnu/services/base.scm (file-system-service): Add #:flags parameter and
  honor it.
* gnu/system.scm (other-file-system-services): Pass FLAGS to
  'file-system-service'.

system: Add 'create-mount-point?' file system option.

* gnu/system/file-systems.scm (<file-system>)[create-mount-point?]: New
  field.
* gnu/services/base.scm (file-system-service): Add #:create-mount-point?
  parameter and honor it.
* gnu/system.scm (other-file-system-services): Update
  'file-system-service' call accordingly.
* doc/guix.texi (File Systems): Document it.

system: Add e2fsprogs to the base packages.

* gnu/system.scm (%base-packages): Add E2FSPROGS.

system: Use kmod instead of module-init-tools.

* gnu/system.scm (%base-packages): Use kmod instead of
  module-init-tools.

system: Add 'nano' and 'lsof' to the base packages.

* gnu/system.scm (%base-packages): Add NANO and LSOF.

system: Add 'which' to the base packages.

* gnu/system.scm (%base-packages): Add WHICH.

system: Remove erroneous system binding in profile maker.

Partly fixes <http://bugs.gnu.org/18002>.
Reported by David Thompson <dthompson2@worcester.edu>.

* gnu/system.scm (union): Remove #:system parameter, which was unused.

linux-initrd: Rename 'qemu-initrd' to 'base-initrd'.

* gnu/system/linux-initrd.scm (qemu-initrd): Rename to...
  (base-initrd): ... this.
* gnu/system.scm (<operating-system>)[initrd]: Update accordingly.
* gnu/system/vm.scm (expression->derivation-in-linux-vm,
  system-disk-image, virtualized-operating-system): Likewise.

system: Set $LINUX_MODULE_DIRECTORY as a function or /run/booted-system.

* gnu/system.scm (etc-directory): Remove #:kernel parameter.  Set
  LINUX_MODULE_DIRECTORY as a function or /run/booted-system.
  (operating-system-etc-directory): Update accordingly.

system: Add a 'system?' field to user accounts.

* gnu/system/shadow.scm (<user-account>)[system?]: New field.
* gnu/system.scm (user-account->gexp): Add it.
* guix/build/activation.scm (add-user): Add #:system? parameter and
  honor it.
  (activate-users+groups): Handle the 'system?' part of user tuples.
  Pass it to 'add-user'.  Don't create PROFILE-DIR when SYSTEM? is
  true.
* gnu/services/dbus.scm (dbus-service): Add 'system?' field for
  "messagebus" account.
* gnu/services/base.scm (guix-build-accounts): Likewise.
* gnu/services/avahi.scm (avahi-service): Likewise.

system: Adjust the set of fields with default values.

* gnu/system.scm (<operating-system>)[file-systems]: Remove default.
  [locale]: Add default value.

guix system: Add 'reconfigure' action.

* guix/scripts/system.scm (%system-profile): New variable.
  (switch-to-system, previous-grub-entries): New procedures.
  (unless-file-not-found): New macro.
  (show-help): Add 'reconfigure'.
  (guix-system): Handle it.
* gnu/system.scm: Export 'operating-system-activation-script'.
* doc/guix.texi (Invoking guix system): Document it.

system: Support the addition of old entries in the GRUB menu.

* gnu/system.scm (operating-system-grub.cfg): Add 'old-entries'
  parameter.  Pass it to 'grub-configuration-file'.
* gnu/system/grub.scm (grub-configuration-file): Add #:old-entries
  parameter.  Honor it.

system: Store boot parameters in the system derivation.

* gnu/system.scm (operating-system-parameters-file): New procedure.
  (operating-system-derivation): Use it to produce a 'parameters' files.

system: Factorize GRUB menu entry label.

* gnu/system.scm (kernel->grub-label): New procedure.
  (operating-system-grub.cfg): Use it.

services: Add udev service, and add it to '%base-services'.

* gnu/services/base.scm (udev-service): New procedure.
  (%base-services): Use it.
* gnu/system.scm (%base-packages): Add UDEV.

system: Augment the default set of groups.

* gnu/system/shadow.scm (%base-groups): New variable.
* gnu/system.scm (<operating-system>)[groups]: Use it as the default.

Merge branch 'core-updates'