gnu: elfutils: Add synopsis and description.

* gnu/packages/elf.scm (elfutils): Add synopsis and description.

list-packages: Add links to Hydra for mips64el-linux.

* build-aux/list-packages.scm (package->sxml): Add 'url' call for
  mips64el-linux.

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'.

linux-initrd: Wait for devices to appear when resolving a label.

* guix/build/linux-initrd.scm (canonicalize-device-spec): Add #:title
  parameter.  When resolving a label, wait a little and try several
  times before bailing out.

Revert "gnu: hurd: Add Hurd Minimal."

This reverts commit bc046a94dec2afadbc1ee3957f13098a8d8b393c,
which referred to uncommitted things ('glibc/hurd-headers'.)

gnu: hurd: Add Hurd Minimal.

* gnu/packages/hurd.scm (hurd-minimal): New variable.
* gnu/packages/patches/hurd-minimal.patch: New patch.
* gnu-system.am (dist_patch_DATA): Add it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

services: syslogd: Write fewer messages to /dev/console.

* gnu/services/base.scm (syslog-service)[contents]: Remove "kern.*" from
  /dev/console.

linux-initrd: Actually create /dev/console.

* guix/build/linux-initrd.scm (make-essential-device-nodes): Add
  "dev/console".

hydra: Make USB installation image smaller.

* build-aux/hydra/gnu-system.scm (qemu-jobs): Reduce size of 'usb-image'
  to 630 MiB.

derivations: Add #:allowed-references 'derivation' parameter.

* guix/derivations.scm (derivation): Add #:allowed-references
  parameter.
  [user+system-env-vars]: Honor it.
* tests/derivations.scm ("derivation #:allowed-references, ok",
  "derivation #:allowed-references, not allowed",
  "derivation #:allowed-references, self allowed",
  "derivation #:allowed-references, self not allowed"): New tests.
* doc/guix.texi (Derivations): Document #:allowed-references.

gnu: util-linux: Remove dependency on Perl.

* gnu/packages/linux.scm (util-linux)[source](patches): New field.
* gnu/packages/patches/util-linux-perl.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.

linux-initrd: Make more device nodes for SCSI disks and CD-ROM devices.

* guix/build/linux-initrd.scm (make-disk-device-nodes): New procedure.
  (make-essential-device-nodes): Use it.  Make more devices nodes for
  SCSI disks and CD-ROM devices.

linux-initrd: Gracefully handle missing /dev nodes.

* guix/build/linux-initrd.scm (partition-label-predicate): Catch
  'system-error' around 'read-ext2-superblock'; return #f upon ENOENT.

hydra: Build the installation image.

* build-aux/hydra/gnu-system.scm (demo-os): New procedure.
  (qemu-jobs): Build for both x86_64-linux and i686-linux.  Add
  'usb-image' job that builds INSTALLATION-OS.

Add (gnu system install).

* gnu/system/install.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

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 more options for 'mingetty-service'.

* gnu/services/base.scm (mingetty-service): Add #:auto-login,
  #:login-program, and #:login-pause? parameters and honor them.

linux-initrd: Gracefully deal with partitions with no label.

* guix/build/linux-initrd.scm (partition-label-predicate): Check whether
  'ext2-superblock-volume-name' returns #f, and return #f if it does.

gnu: Move libarchive to (gnu packages backup).

* gnu/packages/compression.scm (libarchive): Move to...
* gnu/packages/backup.scm (libarchive): ... here.
  Import (guix licenses) with #:renamer to avoid conflicting 'zlib'
  bindings.

vm: disk-image: Specify the root file system using a label.

* gnu/system/vm.scm (system-disk-image)[root-label]: New variable.
  Use it for the root file system, and pass it as #:file-system-label to
  'qemu-image'.