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, 4 insertions, 1 deletions

diff --git a/doc/images/service-graph.dot b/doc/images/service-graph.dot
index 3397b878e9..04f231bb09 100644
--- a/doc/images/service-graph.dot
+++ b/doc/images/service-graph.dot
@@ -4,7 +4,8 @@ digraph "Service Type Dependencies" {
   etc [shape = box, fontname = Helvetica];
   accounts [shape = box, fontname = Helvetica];
   activation [shape = box, fontname = Helvetica];
-  boot [shape = house, fontname = Helvetica];
+  boot [shape = box, fontname = Helvetica];
+  system [shape = house, fontname = Helvetica];
   lshd -> dmd;
   lshd -> pam;
   udev -> dmd;
@@ -32,4 +33,6 @@ digraph "Service Type Dependencies" {
   guix -> dmd;
   guix -> activation;
   guix -> accounts;
+  boot -> system;
+  etc -> system;
 }