linux-initrd: Allow use of volume labels in 'file-system' declarations.

* guix/build/linux-initrd.scm (%ext2-endianness, %ext2-sblock-magic,
  %ext2-sblock-creator-os, %ext2-sblock-uuid, %ext2-sblock-volume-name):
  New macros.
  (read-ext2-superblock, ext2-superblock-uuid,
  ext2-superblock-volume-name, disk-partitions,
  partition-label-predicate, find-partition-by-label,
  canonicalize-device-spec): New procedures.
  (mount-file-system): Use 'canonicalize-device-spec' on SOURCE.
  (boot-system): Likewise for ROOT.
* doc/guix.texi (Using the Configuration System): Adjust 'file-system'
  declaration accordingly.

doc: Augment "Package Naming".

* doc/guix.texi (Package Naming): Mention underscores, and give SDL_net
  as an example.

services: nscd: Provide an 'activate' script to make /var/run/nscd.

* gnu/services/base.scm (nscd-service): Add 'activate' field.
* guix/build/install.scm (directives): Remove /var/run/nscd; add
  /var/run.
* doc/guix.texi (Defining Services): Add 'activate' field in example.
  Document it.

guix system: Add 'disk-image' action.

* guix/scripts/system.scm (show-help): Add 'disk-image'.
  (guix-system)[parse-options]: Support 'disk-image' action.
  [option-arguments]: Likewise.
  Handle the 'disk-image' action.
* doc/guix.texi (Invoking guix system): Document 'disk-image'.

Add (gnu) module.

* gnu.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* build-aux/hydra/demo-os.scm: Use (gnu) and strip import list
  accordingly.
* doc/guix.texi (Using the Configuration System): Adjust example
  accordingly.

doc: Show the 'bootloader' field in system example.

* doc/guix.texi (Using the Configuration System): Add 'bootloader'
  field.

guix system: 'guix system init' installs GRUB by default.

* guix/scripts/system.scm (install): Add #:grub?, #:grub.cfg, and
  #:device parameters; honor them.
  (show-help): Document '--no-grub'.
  (%options): Add '--no-grub'.
  (%default-options): Add 'install-grub?'.
  (guix-system): Honor 'install-grub?' option from OPTS.  Adjust
  'install' call accordingly.
* doc/guix.texi (Invoking guix system): Document '--no-grub'.

guix system: Add 'init' sub-command.

* guix/scripts/system.scm (install): New procedure.
  (guix-system)[parse-option]: Remove check for extraneous arguments.
  [match-pair, option-arguments]: New procedures.
  Use 'option-arguments'.  Honor 'init'.
  (show-help): Document 'init'.
* doc/guix.texi (Invoking guix system): Document 'init'.

guix system: Add 'build' action.

* guix/scripts/system.scm (show-help): Document 'build' action.
  (guix-system): Honor 'build' action.
* doc/guix.texi (Invoking guix system): Add 'build' action.

doc: Improve debugging file documentation.

* doc/guix.texi (Installing Debugging Files): Add @cindex.  Remove
  unneeded '-i' in example.  Mention source code an 'directory'.  Link
  to "Build Systems" instead of "Defining Packages".

doc: Add example for --search.

* doc/guix.texi (Invoking guix package): Add LGPLv3 example.

doc: Add a section on perl modules in the packaging guidelines.

* doc/guix.texi (Perl modules): New section explaining the naming of perl
    modules.

doc: Mention Kiselyov's work on "staging".

* doc/guix.texi (G-Expressions): Mention Oleg's work on "staging" in
  footnote.

doc: Minor improvements in "G-Expressions".

* doc/guix.texi (G-Expressions): Show coreutils version number in store
  file name.  Add xref to "Derivations", in documentation of
  'gexp->derivation'.  Fix typo.

system: Add first-class file system declarations.

* gnu/system.scm (<operating-system>)[initrd]: Default to
  'qemu-initrd'.
  (<file-system>): New record type.
  (operating-system-root-file-system): New procedure.
  (operating-system-derivation): Take the device name for GRUB from
  'operating-system-root-file-system'.  Pass the
  'operating-system-initrd' procedure the list of boot file systems.
* gnu/system/linux-initrd.scm (file-system->spec): New procedure.
  (qemu-initrd): Add 'file-systems' parameter, and remove #:mounts
  parameter.
  [file-system-type-predicate]: New procedure.
  [linux-modules]: Use it.
  Adjust #:mounts argument in 'boot-system' call.
  (gnu-system-initrd): Remove.
* gnu/system/vm.scm (%linux-vm-file-systems): New variable.
  (expression->derivation-in-linux-vm): Adjust call to 'qemu-initrd'.
  (virtualized-operating-system): New procedure.
  (system-qemu-image/shared-store-script)[initrd]: Remove.  Use
  'virtualized-operating-system'.  Get the 'initrd' file from OS-DRV.
* guix/build/linux-initrd.scm (mount-qemu-smb-share, mount-qemu-9p):
  Remove.
  (MS_RDONLY, MS_BIND): New global variables.
  (bind-mount): Remove local 'MS_BIND' definition.
  (mount-root-file-system): New procedure, with code formerly in
  'boot-system'.
  (mount-file-system): New procedure.
  (boot-system): Add #:root-fs-type parameter.  Remove 'MS_RDONLY' local
  variable.  Use 'mount-root-file-system' and 'mount-file-system'.
* doc/guix.texi (Using the Configuration System): Add 'file-system'
  declaration.

monads: Hide 'derivation-expression' and 'lower-inputs'.

* guix/monads.scm: Unexport 'lower-inputs' and 'derivation-expression'.
  (text-file*): Add comment about the switch to 'gexp->derivation'.
  (lower-inputs): Add comment about its doom.
  (derivation-expression): Likewise.
* guix/gexp.scm (lower-inputs*): Rename to...
  (lower-inputs): ... this.  Update callers.
* tests/monads.scm (derivation-expression): New procedure.
* doc/guix.texi (The Store Monad): Use 'gexp->derivation' instead of
  'derivation-expression'.  Remove documentation of
  'derivation-expression'.
* guix/ui.scm (read/eval): Use THE-ROOT-MODULE so that macros are
  properly expanded.
* tests/guix-build.sh: Use 'gexp->derivation' instead of
  'derivation-expression'.monads: Hide 'derivation-expression' and 'lower-inputs'.

services: Rewrite using gexps.

* gnu/services.scm (<service>)[inputs]: Remove.
* gnu/system.scm (links): Remove.
  (etc-directory): Add PASSWD and SHADOW to #:inputs.
  (operating-system-boot-script): Pass ETC to 'dmd-configuration-file'.
  (operating-system-derivation): Remove EXTRAS from the union.
* gnu/system/linux.scm (pam-service->configuration): Rewrite in terms of
  'gexp->derivation'.  Compute the contents on the build side.  Expect
  'arguments' to contain a list of gexps.
  (pam-services->directory): Rewrite in terms of 'gexp->derivation'.
  (unix-pam-service): Change 'arguments' to a list of one gexp.
* gnu/system/shadow.scm (<user-account>)[inputs]: Remove.
  [shell]: Change default value to a gexp.
  (passwd-file): Rewrite in terms of 'gexp->derivation'.  Compute
  contents on the build side.
* gnu/services/base.scm (host-name-service, mingetty-service,
  nscd-service, syslog-service, guix-service): Change 'start' and 'stop'
  to gexps; remove 'inputs' field.
  (guix-build-accounts): Change 'shell' field to a gexp.
* gnu/services/networking.scm (static-networking-service): Change
  'start' and 'stop' to gexps; remove 'inputs' field.
* gnu/services/xorg.scm (slim-service): Likewise.
* gnu/services/dmd.scm (dmd-configuration-file): Expect ETC to be a
  derivation.  Change 'config' to a gexp.  Use 'gexp->file' instead of
  'text-file'.
* doc/guix.texi (Defining Services): Update nscd example with gexps, and
  without 'inputs'.  Add xref to "G-Expressions".

Add (guix gexp).

* guix/gexp.scm: New file.
* tests/gexp.scm: New file.
* Makefile.am (MODULES): Add guix/gexp.scm.
  (SCM_TESTS): Add tests/gexp.scm.
* doc/guix.texi (Derivations): Add #:inputs in 'derivation' example.
  Mark 'build-expression->derivation' as deprecated, refer to
  "G-Expressions".  Remove paragraph about code strata.
  (G-Expressions): New node.

doc: Expect to fix typo.

* doc/guix.texi (Build Systems): "except" it is.

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

guix system: Add 'vm-image' action and '--image-size' option.

* guix/scripts/system.scm (%options): Add --image-size.
  (%default-options): Add 'image-size'.
  (guix-system)[parse-options]: Handle the 'vm-image' action.
  Honor them.
  (show-help): Update accordingly.
* doc/guix.texi (Invoking guix system): Add 'vm-image'.