activation: Set the permissions of /etc/sudoers to 440.

* gnu/build/activation.scm (activate-etc): Move 'rm-f' to a local
  'define'.  When TARGET is "sudoers", make it 440.

activation: Make the /bin/sh symlink at activation time.

* gnu/build/install.scm (directives): Remove "/bin/sh".
* gnu/build/activation.scm (activate-/bin/sh): New procedure.
* gnu/system.scm (operating-system-activation-script): Use it.

activation: Make sure /etc/sudoers & co. are regular files.

Before that, 'sudo' would exit with:

  sudo: /etc/sudoers is not a regular file
  sudo: no valid sudoers sources found, quitting

* gnu/build/activation.scm (activate-etc): Check if SOURCE matches
  'file-is-directory?'.  If not, use 'copy-file' instead of 'symlink'.

activation: Remove outdated comment.

* gnu/build/activation.scm (activate-etc): Remove outdated comment.

activation: Factorize the link-or-copy trick.

* gnu/build/activation.scm (link-or-copy): New procedure.
  (activate-setuid-programs): Use it.

Rename (gnu build linux-initrd) to (gnu build linux-boot).

* gnu/build/linux-initrd.scm: Rename to...
* gnu/build/linux-boot.scm: ... this.
* gnu-system.am (GNU_SYSTEM_MODULES): Adjust accordingly.
* gnu/build/activation.scm, gnu/build/vm.scm, gnu/services/base.scm,
  gnu/services/dmd.scm, gnu/system.scm, gnu/system/linux-initrd.scm,
  gnu/system/vm.scm: Adjust accordingly.

Move operating system helpers from (guix build …) to (gnu build …).

* guix/build/activation.scm, guix/build/install.scm,
  guix/build/linux-initrd.scm, guix/build/vm.scm: Move to...
* gnu/build: ... here.
* Makefile.am (MODULES): Remove the above guix/build/ files.
* gnu-system.am (GNU_SYSTEM_MODULES): Add the above gnu/build/ files
  here.
* gnu/services/base.scm, gnu/services/dmd.scm, gnu/system.scm,
  gnu/system/linux-initrd.scm, gnu/system/vm.scm,
  guix/scripts/system.scm: Adjust to the new module names.

system: Add the 'system?' field for user groups.

Suggested by Mark H. Weaver.

* gnu/system/shadow.scm (<user-group>)[system?]: New field.
  (%base-groups): Introduce 'system-group' macro, and use it.
* gnu/system.scm (user-group->gexp): Pass the 'system?' field.
* guix/build/activation.scm (add-group): Add #:system? and honor it.
  (activate-users+groups): Handle the 'system?' field.
* gnu/system/file-systems.scm (%tty-gid): Choose an ID below 1000.
* doc/guix.texi (User Accounts): Document the 'system?' field.

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.

activation: Preserve /etc/groups upon reboots.

This is a followup to e2fcc23.  The /etc/group file would be cleared
when booting.

* guix/build/activation.scm (activate-users+groups)[touch]: Rewrite so
  it does not wipe out FILE's contents.

Merge branch 'master' into core-updates

activation: Only create groups that do not exist yet.

Before that the effect would be to re-create groups at each boot, and
thus remove any members of the groups.

* guix/build/activation.scm (activate-users+groups): Call 'add-group'
  only when (getgrname name) fails.

Merge branch 'master' into core-updates

system: Separate the activation script from the boot script.

* gnu/system.scm (operating-system-activation-script): New procedure,
  containing most of the former 'operating-system-boot-script'.
  (operating-system-boot-script): Call it, and 'primitive-load' its
  result.
* guix/build/activation.scm (%booted-system): Remove.
  (activate-current-system): Remove #:boot? parameter and related code.

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.

activation: Silence warning from 'useradd'.

* guix/build/activation.scm (add-user): Don't pass '--create-home' when
  HOME already exists.

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.

activation: Fix deletion of setuid programs.

* guix/build/activation.scm (activate-setuid-programs): When
  %SETUID-DIRECTORY exists, pass the right file names to 'delete-file'.

system: Add support for setuid binaries.

* gnu/system.scm (<operating-system>)[pam-services, setuid-programs]:
  New fields.
  (etc-directory)[bashrc]: Prepend /run/setuid-programs to $PATH.
  (operating-system-etc-directory): Honor
  'operating-system-pam-services'.
  (%setuid-programs): New variable.
  (operating-system-boot-script): Add (guix build utils) to the set of
  imported modules.  Call 'activate-setuid-programs' in boot script.
* gnu/system/linux.scm (base-pam-services): New procedure.
* guix/build/activation.scm (%setuid-directory): New variable.
  (activate-setuid-programs): New procedure.
* build-aux/hydra/demo-os.scm: Add 'pam-services' field.

system: Add (guix build activation).

* gnu/services/dmd.scm (dmd-configuration-file): Remove 'etc'
  parameter.  Move /etc activation code to...
* guix/build/activation.scm: ... here; new file.
* gnu/system.scm (operating-system-boot-script): Augment script: add
  (guix build activation) to the load path; call 'activate-etc'.
* Makefile.am (MODULES): Add guix/build/activation.scm.