services: Add 'special-files-service-type'.

* gnu/build/activation.scm (activate-/bin/sh): Remove.
(activate-special-files): New procedure.
* gnu/services.scm (activation-script): Remove call to
'activate-/bin/sh'.
(special-files-service-type): New variable.
(extra-special-file): New procedure.
* gnu/services/base.scm (%base-services): Add SPECIAL-FILES-SERVICE-TYPE
instance.
* gnu/tests/base.scm (run-basic-test)[special-files]: New variables.
["special files"]: New test.

1 files changed, 21 insertions, 4 deletions

diff --git a/gnu/services.scm b/gnu/services.scm
index e645889d30..6ac4f1322d 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -72,6 +72,8 @@
             activation-service-type
             activation-service->script
             %linux-bare-metal-service
+            special-files-service-type
+            extra-special-file
             etc-service-type
             etc-directory
             setuid-program-service-type
@@ -336,10 +338,6 @@ ACTIVATION-SCRIPT-TYPE."
                   #~(begin
                       (use-modules (gnu build activation))
 
-                      ;; Make sure /bin/sh is valid and current.
-                      (activate-/bin/sh
-                       (string-append #$(canonical-package bash) "/bin/sh"))
-
                       ;; Make sure the user accounting database exists.  If it
                       ;; does not exist, 'setutxent' does not create it and
                       ;; thus there is no accounting at all.
@@ -413,6 +411,25 @@ ACTIVATION-SCRIPT-TYPE."
   ;; necessary or impossible in a container.
   (service linux-bare-metal-service-type #f))
 
+(define special-files-service-type
+  ;; Service to install "special files" such as /bin/sh and /usr/bin/env.
+  (service-type
+   (name 'special-files)
+   (extensions
+    (list (service-extension activation-service-type
+                             (lambda (files)
+                               #~(activate-special-files '#$files)))))
+   (compose concatenate)
+   (extend append)))
+
+(define (extra-special-file file target)
+  "Use TARGET as the \"special file\" FILE.  For example, TARGET might be
+  (file-append coreutils \"/bin/env\")
+and FILE could be \"/usr/bin/env\"."
+  (simple-service (string->symbol (string-append "special-file-" file))
+                  special-files-service-type
+                  `((,file ,target))))
+
 (define (etc-directory service)
   "Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE."
   (files->etc-directory (service-parameters service)))