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'

system: Prefer packages from %FINAL-INPUTS.

* gnu/packages/base.scm (canonical-package): New procedure.
* gnu/system.scm (%base-packages): Pass BASH, COREUTILS, FINDUTILS,
  GREP, and SED through 'canonical-package'.

Merge branch 'master' into core-updates

system: Tell module-init-tools where to look for modules.

* gnu/packages/linux.scm (module-init-tools)[source](patches): New
  field.
* gnu/packages/patches/module-init-tools-moduledir.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/system.scm (etc-directory): Add #:kernel parameter.  Set
  'LINUX_MODULE_DIRECTORY' in bashrc.
  (operating-system-etc-directory): Pass #:kernel to 'etc-directory'.

system: Rename activation script.

* gnu/system.scm (operating-system-activation-script): Change file name
  to "activate".

system: Define '%base-packages' and use it.

* gnu/system.scm (<operating-system>)[packages]: Change default value to
  %BASE-PACKAGES.
  (%base-packages): New variable.
* gnu/system/install.scm (installation-os): Use it when defining the
  'packages' field.
* doc/guix.texi (Using the Configuration System): Use %BASE-PACKAGES in
  example.  Remove now unneeded module imports.  Explain this.

system: Make sure /run/setuid-programs comes first in $PATH.

* gnu/system.scm (etc-directory) <bashrc>: Move /run/setuid-programs
  first in $PATH.

system: File system sources can be marked as labels or devices.

* gnu/system/file-systems.scm (<file-system>)[title]: New field.
* gnu/services/base.scm (file-system-service): Add #:title parameter.
  In 'start' gexp, use 'canonicalize-device-spec' and honor TITLE.
* gnu/system.scm (other-file-system-services,
  operating-system-root-file-system, operating-system-initrd-file):
  Adjust accordingly.
* gnu/system/linux-initrd.scm (file-system->spec): Likewise.
* gnu/system/vm.scm (system-disk-image): Add 'title' field for the root
  file system.
* guix/build/linux-initrd.scm (mount-file-system): Expect the second
  element of SPEC to be the title.
  (boot-system)[root-mount-point?, root-fs-type]: Likewise.
* gnu/services/dmd.scm (dmd-configuration-file): Select
  'canonicalize-device-spec'.

system: Add 'issue' field.

* gnu/system.scm (<operating-system>)[issue]: New field.
  (%default-issue): New variable.
  (etc-directory): Add #:issue parameter and honor it.
  (operating-system-etc-directory): Adjust call accordingly.
* build-aux/hydra/demo-os.scm: Add 'issue' field.

system: Add 'fusermount' to the default setuid programs.

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