vm: Disable QEMU networking in the disk image initrd.

* gnu/system/linux-initrd.scm (qemu-initrd): Add #:qemu-networking?
  parameter and honor it.
* gnu/system/vm.scm (system-disk-image): Pass #:qemu-networking #f.

vm: Add 'system-disk-image'.

* gnu/system/vm.scm (system-disk-image): New procedure.

vm: Use a para-virtualized disk when creating an image.

* guix/build/vm.scm (load-in-linux-vm): When MAKE-DISK-IMAGE?, use
  '-drive ...,if=virtio' for better performance.
* gnu/system/vm.scm (qemu-image): Use /dev/vda instead of /dev/sda.

vm: Make the image format a parameter.

* guix/build/vm.scm (load-in-linux-vm): Add #:disk-image-format
  parameter; add 'image-file' variable.  Honor DISK-IMAGE-FORMAT.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Add
  #:disk-image-format parameter, and honor it.
  (qemu-image): Likewise.

Add (gnu system file-systems).

This fixes a circular dependency between (gnu system) and (gnu system
linux-initrd), where the latter could end up being compiled before
'file-system-type' was defined as a macro.

* gnu/system.scm (<file-system>, %fuse-control-file-system,
  %binary-format-file-system): Move to...
* gnu/system/file-systems.scm: ... here.  New file.
* build-aux/hydra/demo-os.scm, gnu/system/linux-initrd.scm,
  gnu/system/vm.scm: Use it.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

vm: Make the device name a parameter.

* guix/build/vm.scm (initialize-partition-table): Honor 'device'
  parameter.
  (initialize-hard-disk): Add 'device' parameter and honor it.
* gnu/system/vm.scm (qemu-image): Adjust accordingly.

system: Add 'grub-configuration' record.

* gnu/system/grub.scm (<grub-configuration>): New record type.
  (grub-configuration-file): Add 'config' parameter; remove
  #:default-entry and #:timeout.  Honor CONFIG.
* gnu/system.scm (<operating-system>): Remove 'bootloader-entries'
  field; remove default value for 'bootloader' field.
  (operating-system-grub.cfg): Pass the 'bootloader' field to
  'grub-configuration-file'.
* build-aux/hydra/demo-os.scm (bootloader): New field.

system: Make /run/current-system at activation time.

* gnu/system.scm (etc-directory): Change default value of #:profile.
  Change contents of SHELLS.  Use /run/current-system/profile/{s,}bin in
  BASHRC.
  (operating-system-boot-script)[%modules]: Add (guix build
  linux-initrd).  Add call to 'activate-current-system' in gexp.
  (operating-system-initrd-file, operating-system-grub.cfg): New
  procedures.
  (operating-system-derivation): Don't build grub.cfg here and remove it
  from the file union.
* gnu/system/vm.scm (qemu-image): Remove #:populate.
  (operating-system-build-gid, operating-system-default-contents):
  Remove.
  (system-qemu-image): Remove call to
  'operating-system-default-contents'.  Use 'operating-system-grub.cfg'
  to get grub.cfg.  Add GRUB.CFG to #:inputs.
  (system-qemu-image/shared-store): Likewise, but don't add GRUB.CFG to
  #:inputs.
  (system-qemu-image/shared-store-script): Pass --system kernel option.
* guix/build/activation.scm (%booted-system, %current-system): New
  variables.
  (boot-time-system, activate-current-system): New procedures.
* guix/build/install.scm (evaluate-populate-directive): Add case
  for ('directory name uid gid mode).
  (directives, populate-root-file-system): New procedures.
* guix/build/vm.scm (initialize-hard-disk): Replace calls to
  'evaluate-populate-directive' by a call to
  'populate-root-file-system'.
* gnu/services/dmd.scm (dmd-configuration-file): Use
  /run/current-system/profile/bin.
* gnu/services/xorg.scm (slim-service): Likewise.

system: Add (guix build install) module.

* guix/build/vm.scm (install-grub, evaluate-populate-directive,
  reset-timestamps, register-closure): Move to...
* guix/build/install.scm: ... here.  New file.
* Makefile.am (MODULES): Add it.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Add (guix
  build install) to #:modules.

vm: Support initialization of the store DB when the store is shared.

* gnu/system/vm.scm (qemu-image): Rename #:inputs-to-copy to #:inputs,
  and #:initialize-store? to #:register-closures?.  Add #:copy-inputs?.
  Adjust build gexp accordingly.
  (system-qemu-image): Remove #:initialize-store? argument and add
  #:copy-inputs?.
  (system-qemu-image/shared-store): Add #:inputs, #:register-closures?,
  and #:copy-inputs? arguments.
* guix/build/vm.scm (register-closure): New procedure.
  (MS_BIND): New variable.
  (initialize-hard-disk): Rename #:initialize-store? to
  #:register-closures?, #:closures-to-copy to #:closures, and add
  #:copy-closures?.
  Add 'target-directory' and 'target-store' variables.
  Call 'populate-store' only when COPY-CLOSURES?.
  Bind-mount the store to TARGET-STORE when REGISTER-CLOSURES? and not
  COPY-CLOSURES?.  Add call to 'register-closure'.

vm: Keep acceptable file systems from the original OS.

* gnu/system/vm.scm (virtualized-operating-system): Instead of
  completely overriding 'file-systems', use 'remove' to filter out some
  of those declared in OS.
  (system-qemu-image): Likewise.

vm: Pass '-serial stdio' in the run-vm.sh.

* gnu/system/vm.scm (system-qemu-image/shared-store-script): Add
  '-serial stdio'.

system: Move skeleton code to (gnu system shadow).

* gnu/system.scm (default-skeletons, skeleton-directory): Move to...
* gnu/system/shadow.scm: ... here.

system: Make accounts and groups at activation time.

* gnu/services/base.scm (guix-build-accounts): Remove #:gid parameter;
  add #:group.  Remove 'password' and 'gid' fields in 'user-account'
  form, and add 'group'.
  (guix-service): Remove #:build-user-gid parameter.  Remove 'id' field
  in 'user-group' form.
* gnu/system.scm (etc-directory): Remove #:groups and #:accounts.  No
  longer produce files "passwd", "shadow", and "group".  Adjust caller
  accordingly.
  (%root-account): New variable.
  (operating-system-accounts): Add 'users' variable.  Add %ROOT-ACCOUNT
  only of 'operating-system-users' doesn't already contain a root
  account.
  (user-group->gexp, user-account->gexp): New procedures.
  (operating-system-boot-script): Add calls to 'setenv' and
  'activate-users+groups' in gexp.
* gnu/system/linux.scm (base-pam-services): Add PAM services for
  "user{add,del,mode}" and "group{add,del,mod}".
* gnu/system/shadow.scm (<user-account>)[gid]: Rename to...
  [group]: ... this.
  [supplementary-groups]: New field.
  [uid, password]: Default to #f.
  (<user-group>)[id]: Default to #f.
  (group-file, passwd-file): Remove.
* gnu/system/vm.scm (operating-system-default-contents)[user-directories]:
  Remove.  Add "/home" to the directives.
* guix/build/activation.scm (add-group, add-user,
  activate-users+groups): New procedures.

vm: Fix recently-introduced regression in 'operating-system-services' use.

* gnu/system/vm.scm (operating-system-build-gid): Adjust to new return
  type of 'operating-system-services' introduced in 217a5b8.

linux-initrd: Check the root and other early file systems.

* gnu/system.scm (operating-system-derivation)[boot-file-systems]: Keep "/".
* gnu/system/linux-initrd.scm (file-system->spec): Keep the 'check?'
  flag.
  (qemu-initrd)[helper-packages]: New variable.  Pass it as #:to-copy.
  <gexp>: Add 'set-path-environment-variable' call.  Remove #:unionfs
  argument for 'boot-system'.
* gnu/system/vm.scm (%linux-vm-file-systems): Add 'check?' field/
  (virtualized-operating-system): Likewise for the "9p" file system.
* guix/build/linux-initrd.scm (mount-root-file-system): Change #:unionfs
  default.  Call 'check-file-system' before mounting ROOT, when
  VOLATILE-ROOT? is false.
  (check-file-system): New procedure.
  (mount-file-system): Honor 'check?' element in list; add
  'check-file-system' call.
  (boot-system): Remove #:root-fs-type and #:unionfs parameters.
  [root-mount-point?, root-fs-type]: New variables.
  Call 'mount-file-system' on all MOUNTS but "/".

vm: Provide a root partition for the freestanding VM image.

Fixes a regression introduced in 83bcd0b.

* gnu/system/vm.scm (system-qemu-image): Override the 'file-systems'
  field of OS.  Add #:file-system-type parameter and honor it.

vm: Make root file system type a parameter, and default to ext4.

* gnu/system/vm.scm (qemu-image): Add #:file-system-type parameter.
  Pass it to 'initialize-hard-disk'.
* guix/build/linux-initrd.scm (mount-root-file-system): Always honor
  TYPE.
  (boot-system): Change #:root-fs-type to default to "ext4".  Update
  docstring.
* guix/build/vm.scm (initialize-hard-disk): Remove #:mkfs parameter; add
  #:file-system-type.  Adjust 'mkfs' invocation and 'mount' call to
  honor #:file-system-type.

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.

system: Add 'sudo' to the setuid programs, and handle /etc/sudoers.

* gnu/system.scm (<operating-system>)[groups]: Change default to just
  the 'root' group.
  [sudoers]: New field.
  (etc-directory): Add #:sudoers parameter.  Add 'sudoers' to the
  file union.
  (operating-system-etc-directory): Pass #:sudoers to 'etc-directory'.
  (%setuid-programs): Add 'sudo'.
  (%sudoers-specification): New variable.
* gnu/system/linux.scm (base-pam-services): Add 'sudo'.
* build-aux/hydra/demo-os.scm: Add 'groups' field; add 'guest' to the
  'wheel' group.