services: Add docker.

* gnu/services/docker.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Miscellaneous Services): Document the service.

doc/guix.texi

@@ -22118,6 +22118,33 @@ The following is an example @code{dicod-service} configuration.
                     %dicod-database:gcide))))
 @end example
 
+@cindex Docker
+@subsubheading Docker Service
+
+The @code{(gnu services docker)} module provides the following service.
+
+@defvr {Scheme Variable} docker-service-type
+
+This is the type of the service that runs @url{http://www.docker.com,Docker},
+a daemon that can execute application bundles (sometimes referred to as
+``containers'') in isolated environments.
+
+@end defvr
+
+@deftp {Data Type} docker-configuration
+This is the data type representing the configuration of Docker and Containerd.
+
+@table @asis
+
+@item @code{package} (default: @code{docker})
+The Docker package to use.
+
+@item @code{containerd} (default: @var{containerd})
+The Containerd package to use.
+
+@end table
+@end deftp
+
 @node Setuid Programs
 @subsection Setuid Programs
 

gnu/local.mk

@@ -483,6 +483,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/services/desktop.scm			\
   %D%/services/dict.scm				\
   %D%/services/dns.scm				\
+  %D%/services/docker.scm			\
   %D%/services/authentication.scm		\
   %D%/services/games.scm			\
   %D%/services/kerberos.scm			\

gnu/services/docker.scm

@@ -0,0 +1,94 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 Danny Milosavljevic <dannym@scratchpost.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu services docker)
+  #:use-module (gnu services)
+  #:use-module (gnu services configuration)
+  #:use-module (gnu services base)
+  #:use-module (gnu services dbus)
+  #:use-module (gnu services shepherd)
+  #:use-module (gnu system shadow)
+  #:use-module (gnu packages docker)
+  #:use-module (guix records)
+  #:use-module (guix gexp)
+  #:use-module (guix packages)
+
+  #:export (docker-configuration
+            docker-service-type))
+
+(define-configuration docker-configuration
+  (docker
+   (package docker)
+   "Docker daemon package.")
+  (containerd
+   (package containerd)
+   "containerd package."))
+
+(define %docker-accounts
+  (list (user-group (name "docker") (system? #t))))
+
+(define (%containerd-activation config)
+  (let ((state-dir "/var/lib/containerd"))
+    #~(begin
+        (use-modules (guix build utils))
+        (mkdir-p #$state-dir))))
+
+(define (%docker-activation config)
+  (%containerd-activation config)
+  (let ((state-dir "/var/lib/docker"))
+    #~(begin
+        (use-modules (guix build utils))
+        (mkdir-p #$state-dir))))
+
+(define (containerd-shepherd-service config)
+  (let* ((package (docker-configuration-containerd config)))
+    (shepherd-service
+           (documentation "containerd daemon.")
+           (provision '(containerd))
+           (start #~(make-forkexec-constructor
+                     (list (string-append #$package "/bin/containerd"))))
+           (stop #~(make-kill-destructor)))))
+
+(define (docker-shepherd-service config)
+  (let* ((docker (docker-configuration-docker config)))
+    (shepherd-service
+           (documentation "Docker daemon.")
+           (provision '(dockerd))
+           (requirement '(containerd))
+           (start #~(make-forkexec-constructor
+                     (list (string-append #$docker "/bin/dockerd")
+                           "-p" "/var/run/docker.pid")
+                     #:pid-file "/var/run/docker.pid"
+                     #:log-file "/var/log/docker.log"))
+           (stop #~(make-kill-destructor)))))
+
+(define docker-service-type
+  (service-type (name 'docker)
+                (description "Provide capability to run Docker application
+bundles in Docker containers.")
+                (extensions
+                 (list
+                  (service-extension activation-service-type
+                                     %docker-activation)
+                  (service-extension shepherd-root-service-type
+                                     (lambda args
+                                       (list (apply containerd-shepherd-service args)
+                                             (apply docker-shepherd-service args))))
+                  (service-extension account-service-type
+                                     (const %docker-accounts))))
+                (default-value (docker-configuration))))