services: Add 'system-service-type'.

* gnu/services.scm (system-derivation): New procedure.
  (system-service-type): New variable.
  (boot-script-entry): New procedure.
  (boot-service-type): Extend SYSTEM-SERVICE-TYPE.
  (etc-entry): New procedure.
  (etc-service-type): Extend SYSTEM-SERVICE-TYPE.
  (fold-services): Change default #:target-type to SYSTEM-SERVICE-TYPE.
* gnu/system.scm (operating-system-directory-base-entries): New procedure.
  (essential-services): Use it.  Add an instance of
  SYSTEM-SERVICE-TYPE.
  (operating-system-boot-script): Pass #:target-type to 'fold-services'.
  (operating-system-derivation): Rewrite in terms of 'fold-services'.
* gnu/system/linux-container.scm (system-container): Remove.
  (container-script): Use 'operating-system-derivation'.
* guix/scripts/system.scm (export-extension-graph): Replace
  BOOT-SERVICE-TYPE by SYSTEM-SERVICE-TYPE.
* doc/images/service-graph.dot: Add 'system' node and edges.
* doc/guix.texi (Service Composition): Mention SYSTEM-SERVICE-TYPE.
  (Service Reference): Document it.  Update 'fold-services'
  documentation.

1 files changed, 3 insertions, 15 deletions

diff --git a/gnu/system/linux-container.scm b/gnu/system/linux-container.scm
index c2eb773931d..4f38c5cb0aa 100644
--- a/gnu/system/linux-container.scm
+++ b/gnu/system/linux-container.scm
@@ -47,20 +47,6 @@
        (check? #f)
        (create-mount-point? #t)))))
 
-(define (system-container os)
-  "Return a derivation that builds OS as a Linux container."
-  (mlet* %store-monad
-      ((profile (operating-system-profile os))
-       (etc  -> (operating-system-etc-directory os))
-       (boot    (operating-system-boot-script os #:container? #t))
-       (locale  (operating-system-locale-directory os)))
-    (lower-object
-     (file-union "system-container"
-                 `(("boot" ,#~#$boot)
-                   ("profile" ,#~#$profile)
-                   ("locale" ,#~#$locale)
-                   ("etc" ,#~#$etc))))))
-
 (define (containerized-operating-system os mappings)
   "Return an operating system based on OS for use in a Linux container
 environment.  MAPPINGS is a list of <file-system-mapping> to realize in the
@@ -95,7 +81,9 @@ that will be shared with the host system."
                                (operating-system-file-systems os)))
          (specs        (map file-system->spec file-systems)))
 
-    (mlet* %store-monad ((os-drv (system-container os)))
+    (mlet* %store-monad ((os-drv (operating-system-derivation
+                                  os
+                                  #:container? #t)))
 
       (define script
         #~(begin