[bug#70542] [PATCH 1/4] file-systems: Add requirements field to file-systems

[Richard Sent]

* gnu/system/file-systems.scm (file-system): Add requirements field to the
file-system record. This field will be used for adding additional Shepherd
requirements to a file system Shepherd service.
* doc/guix.texi: Add documentation for file-system requirements.

Change-Id: If0392db03d48e8820aa53df1df482c12ec72e1a5
---
 doc/guix.texi               | 13 +++++++++++++
 gnu/system/file-systems.scm |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/doc/guix.texi b/doc/guix.texi
index 65af136e61..80b24e2de9 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -17751,6 +17751,19 @@ File Systems
 
 Another example is a file system that depends on a mapped device, for
 example for an encrypted partition (@pxref{Mapped Devices}).
+
+@item @code{requirements} (default: @code{'()})
+This is a list of symbols denoting Shepherd requirements that must be
+met before mounting the file system.
+
+As an example, an NFS file system would typically have a requirement for
+@code{networking}.
+
+Typically, file systems are mounted before most other Shepherd services
+are started. However, file systems with a non-empty requirements field
+are mounted after Shepherd services have begun. Any Shepherd service
+that depends on a file system with a non-empty requirements field must
+depend on it directly and not on the generic symbol @code{file-systems}.
 @end table
 @end deftp
 
diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index af0567bd3e..76a51a2b69 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -57,6 +57,7 @@ (define-module (gnu system file-systems)
             file-system-repair
             file-system-create-mount-point?
             file-system-dependencies
+            file-system-requirements
             file-system-location
 
             file-system-type-predicate
@@ -185,6 +186,8 @@ (define-record-type* <file-system> file-system
                        (default #f))
   (dependencies     file-system-dependencies      ; list of <file-system>
                     (default '()))                ; or <mapped-device>
+  (requirements     file-system-requirements      ; list of symbols
+                    (default '()))
   (location         file-system-location
                     (default (current-source-location))
                     (innate)))
-- 
2.41.0