linux-boot: Don't fail if /root/etc/mtab is a dangling symlink.

Reported Joshua Grant.
Patch suggested by Mark H Weaver.

* gnu/build/linux-boot.scm (mount-root-file-system): Use
  'false-if-exception' instead of 'when (file-exists? ...)' to account
  for dangling symlinks.

Merge branch 'master' into core-updates

linux-boot: Make /etc/mtab a symlink to /proc/self/mounts.

Fixes <http://bugs.gnu.org/19491>.

* gnu/build/linux-boot.scm (mount-root-file-system): Make /root/etc/mtab
  a symlink to /proc/self/mounts.
* gnu/build/file-systems.scm (mount-file-system): Don't update /etc/mtab.
* guix/build/syscalls.scm (mount, umount): Have #:update-mtab? default to
  #f.

Merge branch 'master' into 'core-updates'.

linux-boot: Load modules and their dependencies, à la 'modprobe'.

* gnu/build/linux-boot.scm: Use (gnu build linux-modules).
  (load-linux-module*): Remove.
  (boot-system): Add #:linux-module-directory parameter.
  [lookup-module]: New procedure.
  Call 'current-module-debugging-port'.  Pass #:lookup-module to
  'load-linux-module*'.  Map LOOKUP-MODULE on LINUX-MODULES.
* gnu/system/linux-initrd.scm (base-initrd): Adjust 'boot-system' call
  accordingly.  Adjust #:modules argument as well.
* gnu/system.scm (operating-system-activation-script)[%modules]: Likewise.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Likewise.

linux-boot: Call 'pre-mount' before 'mount-root-file-system'.

Partly fixes <http://bugs.gnu.org/19190>.
Reported by Nikita Karetnikov <nikita@karetnikov.org>.

* gnu/build/linux-boot.scm (boot-system): Move PRE-MOUNT call before
  'mount-root-file-system' is called.

linux-boot: Error out when 'pre-mount' returns #f.

* gnu/build/linux-boot.scm (boot-system): Call 'error' when PRE-MOUNT
  returns #f.

linux-boot: Don't catch exceptions thrown by 'mount-root-file-system'.

* gnu/build/linux-boot.scm (mount-root-file-system): Remove 'catch #t'
  around body.  This was unneeded and even inconvenient because this
  procedure is called from within 'call-with-error-handling' already.

linux-boot: Make more disk partition block devices.

Reported by nebuli on #guix.

* gnu/build/linux-boot.scm (make-disk-device-nodes): Make 16 block
  devices for disk partitions.

system: Add support for boot-time mapped devices.

* gnu/build/linux-boot.scm (boot-system): Add #:pre-mount parameter and
  honor it.
* gnu/system/linux-initrd.scm (base-initrd): Add #:mapped-devices
  parameter.  Add 'device-mapping-commands' variable, and use it to
  build the #:pre-mount argument of 'boot-system'.
* gnu/system.scm (mapped-device-user,
  operating-system-user-mapped-devices,
  operating-system-boot-mapped-devices): New procedures.
  (device-mapping-services): Use 'operating-system-user-mapped-devices'
  instead of 'operating-system-mapped-devices'.
  (operating-system-initrd-file): Call the initrd with #:mapped-devices.

linux-initrd: Remove now obsolete #:guile-modules-in-chroot? parameter.

* gnu/build/linux-boot.scm (boot-system): Remove
  #:guile-modules-in-chroot? and related code.
* gnu/system/linux-initrd.scm (base-initrd): Likewise.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Remove
  #:guile-modules-in-chroot? argument in 'base-initrd' call.

Merge branch 'master' into core-updates

Conflicts:
	gnu/packages/image.scm

linux-initrd: Store Linux modules in a normal store directory.

* gnu/system/linux-initrd.scm (expression->initrd): Remove #:linux and
  #:linux-modules parameters.  Remove call to
  'float-linux-module-directory'.
  (base-initrd): Add call to 'float-linux-module-directory'.  Use it in
  #:linux-modules argument in the gexp.  Remove #:linux and
  #:linux-modules arguments to 'expression->initrd'.
* gnu/build/linux-initrd.scm (build-initrd): Remove
  #:linux-module-directory parameter.  Don't create 'modules'
  sub-directory.
* gnu/build/linux-boot.scm (boot-system): Mentin that LINUX-MODULES is a
  list of absolute file names.  Don't prepend "/modules/" to
  LINUX-MODULES.
* doc/guix.texi (Initial RAM Disk): Adjust accordingly.

linux-initrd: Copy all the script's closure to the initrd.

* gnu/system/linux-initrd.scm (expression->initrd): Remove calls to
  'imported-modules' and 'compiled-modules'.  Use 'gexp->script' with
  EXP.  Add the result to TO-COPY.  Make /init a symlink to that script,
  and copy its closure into the "contents" directory.  Add fake
  /proc/self/exe symlink.
* gnu/build/linux-boot.scm (load-linux-module*): Add comment about mmap.
* gnu/system/vm.scm (system-qemu-image/shared-store-script): Add "-m
  256".  This turns out to be needed for initrds containing things like
  e2fsck and several modules; with the default of 128 MiB, loading
  libahci.ko may fail with -1.

Merge branch 'master' into core-updates

Merge branch 'master' into core-updates

Conflicts:
	gnu/packages/base.scm

linux-initrd: Wait a bit longer for partitions to appear.

Reported by Sveltana on #guix.

* guix/build/linux-initrd.scm (canonicalize-device-spec): Increase
  MAX-TRIALS.  Add "waiting for partition" 'format' call.

Merge branch 'master' into core-updates

linux-initrd: Do not create /etc/resolv.conf.

* guix/build/linux-initrd.scm (configure-qemu-networking): Don't create
  /etc/resolv.conf.

Merge branch 'master' into core-updates