system: Add support for Linux-style mapped devices.

* gnu/system/file-systems.scm (<mapped-device>): New record type.
* gnu/system.scm (<operating-system>)[mapped-devices]: New field.
  (luks-device-mapping): New procedure.
  (other-file-system-services)[device-mappings, requirements]: New
  procedures.  Pass #:requirements to 'file-system-service'.
  (device-mapping-services): New procedure.
  (essential-services): Use it.  Append its result to the return value.
  (operating-system-initrd-file): Add comment.
* gnu/services/base.scm (file-system-service): Add #:requirements
  parameter and honor it.
  (device-mapping-service): New procedure.
* gnu/system/linux-initrd.scm (base-initrd): Add comment.

1 files changed, 20 insertions, 1 deletions

diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index 48c4fc7e77..90e2b0c796 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -37,7 +37,13 @@
             %pseudo-terminal-file-system
             %devtmpfs-file-system
 
-            %base-file-systems))
+            %base-file-systems
+
+            mapped-device
+            mapped-device?
+            mapped-device-source
+            mapped-device-target
+            mapped-device-command))
 
 ;;; Commentary:
 ;;;
@@ -128,4 +134,17 @@
         %pseudo-terminal-file-system
         %shared-memory-file-system))
 
+
+
+;;;
+;;; Mapped devices, for Linux's device-mapper.
+;;;
+
+(define-record-type* <mapped-device> mapped-device
+  make-mapped-device
+  mapped-device?
+  (source    mapped-device-source)                ;string
+  (target    mapped-device-target)                ;string
+  (command   mapped-device-command))              ;source target -> gexp
+
 ;;; file-systems.scm ends here