file-systems: Use a second 'mount' call for read-only bind mounts.

* gnu/build/file-systems.scm (MS_REMOUNT): New constant.
  (mount-file-system): Add 'flags' local variable.   When FLAGS has
  MS_BIND & MS_RDONLY, call 'mount' with MS_REMOUNT.
* gnu/services/base.scm (file-system-service) <start>: Likewise.

Merge branch 'core-updates'

Merge branch 'master' into core-updates

Conflicts:
	gnu-system.am
	gnu/packages/gstreamer.scm

services: Explicitly refer to Shadow when requiring the 'nologin' shell.

* gnu/services/avahi.scm (avahi-service): Change 'shell' to a gexp
  referring to "nologin" in the SHADOW package.
* gnu/services/dbus.scm (dbus-service): Likewise.
* gnu/services/networking.scm (ntp-service, tor-service): Likewise.

Merge branch 'master' into core-updates

services: Add upower.

* gnu-system.am (GNU_SYSTEM_MODULES): Add gnu/services/upower.scm.
* gnu/services/upower.scm: New file, defining a upower service.
* doc/guix.texi (Various Services): Mention it.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

doc: Add example showing how to customize 'nscd-service'.

* doc/guix.texi (Name Service Switch): Add link to nss-mdns.  Add
  example show how to pass #:name-services to 'nscd-service'.
  (Base Services): Add link from 'nscd-service' to the above.
* gnu/services/base.scm (nscd-service): Update docstring accordingly.

gnu: Add colord service.

* gnu-system.am (GNU_SYSTEM_MODULES): Add gnu/services/colord.scm.
* gnu/services/colord.scm: New file.
* doc/guix.texi (Various Services): Document it.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

Merge branch 'master' into core-updates

services: lsh: Change #:initialize? to default to #t.

* gnu/services/ssh.scm (lsh-service): Change #:initialize? to default
  to #t.
* doc/guix.texi (Using the Configuration System): Remove #:initialize? #t
  from example.
  (Networking Services): Adjust accordingly.

services: syslog-service: Add 'config-file' argument.

* gnu/services/base.scm (syslog-service): Add 'config-file' keyword
argument.
* doc/guix.texi (Base Services): Document it.

Merge branch 'master' into core-updates

services: guix-service: Add service documentation.

* gnu/services/base.scm (guix-service): Add 'documentation' field to the
  service.

services: Add 'lirc-service'.

* gnu/services/lirc.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Various Services): New node.  Document 'lirc-service'.

Merge branch 'master' into core-updates

services: guix-service: Add 'lsof' and 'lsh' to guix-daemon's $PATH.

* gnu/services/base.scm (guix-service): Add #:lsof and #:lsh parameters.
  [start]: Pass #:environment-variables to 'make-forkexec-constructor'.

Merge branch 'master' into core-updates

services: guix-service: Remove extraneous monadism.

* gnu/services/base.scm (guix-build-accounts): Remove unneeded
  'with-monad'.
  (guix-service): Adjust accordingly.

services: slim: Pass SESSION to ~/.xsession as "$1".

* gnu/services/xorg.scm (xinitrc)[builder]: Pass SESSION to ~/.xsession.

services: slim: Allow non-absolute path to be used as session command.

* gnu/services/xorg.scm (xinitrc)[builder]: Don't check the existence
  of COMMAND.  Only run ~/.xsession when it exists.