[bug#41820] [PATCH] file-systems: Add record type <nfs-share> for a file system device.

[Stefan]

* doc/guix.texi: Add description for 'nfs-share'.
* gnu/bootloader/grub.scm (grub-root-search): Support 'nfs-share'.
* gnu/build/file-systems.scm (canonicalize-device-spec): Support 'nfs-share'.
* gnu/build/linux-boot.scm (device-string->file-system-device): Support
'nfs-share'.
* gnu/machine/ssh.scm (machine-check-file-system-availability): Support
'nfs-share'.
* gnu/services/base.scm (file-system->fstab-entry): Support 'nfs-share'.
* gnu/system.scm (read-boot-parameters, device-sexp->device, device->sexp):
Support 'nfs-share'.
* gnu/system/file-systems.scm (<nfs-share>): New record type with printer.
(nfs-share): New function to conditionally construct an 'nfs-share' record.
(nfs-share->string): New function.
(nfs-share?): New predicate.
(file-system-device->string, file-system->spec, spec->file-system): Support
'nfs-share'.
* guix/scripts/system.scm (display-system-generation, check-initrd-modules):
Support 'nfs-share'.
---
 doc/guix.texi               | 38 ++++++++++++++++++++++++++++++-------
 gnu/bootloader.scm          |  4 ++--
 gnu/bootloader/grub.scm     |  2 ++
 gnu/build/file-systems.scm  | 12 ++++++------
 gnu/build/linux-boot.scm    |  7 ++++---
 gnu/machine/ssh.scm         | 23 ++++++++++++++++++++++
 gnu/services/base.scm       |  2 ++
 gnu/system.scm              |  4 ++++
 gnu/system/file-systems.scm | 36 +++++++++++++++++++++++++++++++++--
 guix/scripts/system.scm     |  9 +++++++--
 10 files changed, 115 insertions(+), 22 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 15e077a41c..4fd3793a4f 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -11723,10 +11723,10 @@ This is a string specifying the type of the file 
system---e.g.,
 This designates the place where the file system is to be mounted.
 
 @item @code{device}
-This names the ``source'' of the file system.  It can be one of three
-things: a file system label, a file system UUID, or the name of a
-@file{/dev} node.  Labels and UUIDs offer a way to refer to file
-systems without having to hard-code their actual device
+This names the ``source'' of the file system.  It can be one of four
+things: a file system label, a file system UUID, the name of a
+@file{/dev} node, or an NFS share.  Labels and UUIDs offer a way to
+refer to file systems without having to hard-code their actual device
 name@footnote{Note that, while it is tempting to use
 @file{/dev/disk/by-uuid} and similar device names to achieve the same
 result, this is not recommended: These special device nodes are created
@@ -11735,9 +11735,10 @@ mounted.}.
 
 @findex file-system-label
 File system labels are created using the @code{file-system-label}
-procedure, UUIDs are created using @code{uuid}, and @file{/dev} node are
-plain strings.  Here's an example of a file system referred to by its
-label, as shown by the @command{e2label} command:
+procedure, UUIDs are created using @code{uuid}, NFS shares are created
+using @code{nfs-share}, and @file{/dev} nodes are plain strings.  Here's
+an example of a file system referred to by its label, as shown by the
+@command{e2label} command:
 
 @lisp
 (file-system
@@ -11762,6 +11763,29 @@ like this:
   (device (uuid "4dab5feb-d176-45de-b287-9b0a6e4c01cb")))
 @end lisp
 
+@findex nfs-share
+An NFS share is defined in one of the following ways. Please note that
+the NFS server for a root file system needs to be passed as IP address
+via the @code{options} field as @code{"addr="} option.
+
+@lisp
+(file-system
+  (mount-point "/")
+  (type "nfs")
+  (device (nfs-share ":/srv/nfs/guix-root"))
+  (options "addr=10.10.10.10,vers=4.1")
+  (needed-for-boot? #t))
+@end lisp
+
+@lisp
+(file-system
+  (mount-point "/music")
+  (type "nfs")
+  (device (nfs-share "music-server.local:/srv/nfs/music"))
+  (options "vers=4.1")
+  (needed-for-boot? #f))
+@end lisp
+
 When the source of a file system is a mapped device (@pxref{Mapped
 Devices}), its @code{device} field @emph{must} refer to the mapped
 device name---e.g., @file{"/dev/mapper/root-partition"}.
diff --git a/gnu/bootloader.scm b/gnu/bootloader.scm
index 2eebb8e9d9..62c585670b 100644
--- a/gnu/bootloader.scm
+++ b/gnu/bootloader.scm
@@ -77,8 +77,8 @@
   menu-entry make-menu-entry
   menu-entry?
   (label           menu-entry-label)
-  (device          menu-entry-device       ; file system uuid, label, or #f
-                   (default #f))
+  (device          menu-entry-device       ; uuid, file-system-label,
+                   (default #f))           ; nfs-share, or #f
   (device-mount-point menu-entry-device-mount-point
                    (default #f))
   (linux           menu-entry-linux
diff --git a/gnu/bootloader/grub.scm b/gnu/bootloader/grub.scm
index b905ae360c..d82c09a79d 100644
--- a/gnu/bootloader/grub.scm
+++ b/gnu/bootloader/grub.scm
@@ -295,6 +295,8 @@ code."
         ((? file-system-label? label)
          (format #f "search --label --set ~a"
                  (file-system-label->string label)))
+        ((? nfs-share?)
+         "set root=(tftp)")
         ((or #f (? string?))
          #~(format #f "search --file --set ~a" #$file)))))
 
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index ad92d8a496..306cff75fb 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -636,8 +636,8 @@ were found."
 
 ^L
 (define (canonicalize-device-spec spec)
-  "Return the device name corresponding to SPEC, which can be a <uuid>, a
-<file-system-label>, or a string (typically a /dev file name)."
+  "Return the device name corresponding to SPEC, which can be a <uuid>, an
+<nfs-share>, a <file-system-label>, or a string (typically a /dev file name)."
   (define max-trials
     ;; Number of times we retry partition label resolution, 1 second per
     ;; trial.  Note: somebody reported a delay of 16 seconds (!) before their
@@ -661,10 +661,10 @@ were found."
 
   (match spec
     ((? string?)
-     (if (string-contains spec ":/")
-         spec                  ; do not resolve NFS devices
-         ;; Nothing to do, but wait until SPEC shows up.
-         (resolve identity spec identity)))
+     ;; Nothing to do, but wait until SPEC shows up.
+     (resolve identity spec identity))
+    ((? nfs-share?)
+     (nfs-share->string spec))
     ((? file-system-label?)
      ;; Resolve the label.
      (resolve find-partition-by-label
diff --git a/gnu/build/linux-boot.scm b/gnu/build/linux-boot.scm
index 80fe0cfb9d..8a609f6eff 100644
--- a/gnu/build/linux-boot.scm
+++ b/gnu/build/linux-boot.scm
@@ -469,10 +469,11 @@ upon error."
 
   (define (device-string->file-system-device device-string)
     ;; The "--root=SPEC" kernel command-line option always provides a
-    ;; string, but the string can represent a device, a UUID, or a
-    ;; label.  So check for all three.
-    (cond ((string-prefix? "/" device-string) device-string)
+    ;; string, but the string can represent a device, a UUID, an nfs-share,
+    ;; or a label.  So check for all of theme.
+    (cond ((nfs-share device-string #:on-error (const #f)) => identity)
           ((uuid device-string) => identity)
+          ((string-prefix? "/" device-string) device-string)
           (else (file-system-label device-string))))
 
   (display "Welcome, this is GNU's early boot Guile.\n")
diff --git a/gnu/machine/ssh.scm b/gnu/machine/ssh.scm
index 116da86327..aa42a082c2 100644
--- a/gnu/machine/ssh.scm
+++ b/gnu/machine/ssh.scm
@@ -222,6 +222,24 @@ exist on the machine."
                  (message (format #f (G_ "no file system with UUID '~a'")
                                   (uuid->string (file-system-device 
fs))))))))))
 
+  (define (check-nfs-share fs)
+    (define remote-exp
+      (with-imported-modules (source-module-closure
+                              '((gnu build file-systems)))
+        #~(begin
+            (use-modules (gnu build file-systems))
+
+            ;; TODO: Try to mount the share or to ping the server.
+            (nfs-share->string (nfs-share
+                                 #$(nfs-share->string (file-system-device 
fs)))))))
+
+    (remote-let ((result remote-exp))
+      (unless result
+        (raise (condition
+                (&message
+                 (message (format #f (G_ "no nfs-share '~a'")
+                                  (nfs-share->string (file-system-device 
fs))))))))))
+
   (append (map check-literal-file-system
                (filter (lambda (fs)
                          (string? (file-system-device fs)))
@@ -233,6 +251,10 @@ exist on the machine."
           (map check-uuid-file-system
                (filter (lambda (fs)
                          (uuid? (file-system-device fs)))
+                       file-systems))
+          (map check-nfs-share
+               (filter (lambda (fs)
+                         (nfs-share? (file-system-device fs)))
                        file-systems))))
 
 (define (machine-check-initrd-modules machine)
@@ -257,6 +279,7 @@ not available in the initrd."
 
               (define dev
                 #$(cond ((string? device) device)
+                        ((nfs-share? device) (nfs-share->string device))
                         ((uuid? device) #~(find-partition-by-uuid
                                            (string->uuid
                                             #$(uuid->string device))))
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 6ea7ef8e7e..beef30fdf4 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -200,6 +200,8 @@
                                    (file-system-label->string label)))
                    ((? uuid? uuid)
                     (string-append "UUID=" (uuid->string uuid)))
+                   ((? nfs-share? share)
+                    (nfs-share->string share))
                    ((? string? device)
                     device))
                  "\t"
diff --git a/gnu/system.scm b/gnu/system.scm
index d51691fe76..660255b9e9 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -306,6 +306,8 @@ file system labels."
        (bytevector->uuid bv type))
       (('file-system-label (? string? label))
        (file-system-label label))
+      (('nfs-share (? string? share))
+       (nfs-share share))
       ((? bytevector? bv)                         ;old format
        (bytevector->uuid bv 'dce))
       ((? string? device)
@@ -1240,6 +1242,8 @@ such as '--root' and '--load' to <boot-parameters>."
      `(uuid ,(uuid-type uuid) ,(uuid-bytevector uuid)))
     ((? file-system-label? label)
      `(file-system-label ,(file-system-label->string label)))
+    ((? nfs-share? share)
+     `(nfs-share ,(nfs-share->string share)))
     (_
      device)))
 
diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index 0f94577760..13ef38e490 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -59,6 +59,10 @@
             file-system-label?
             file-system-label->string
 
+            nfs-share
+            nfs-share?
+            nfs-share->string
+
             file-system->spec
             spec->file-system
             specification->file-system-mapping
@@ -102,7 +106,8 @@
 (define-record-type* <file-system> %file-system
   make-file-system
   file-system?
-  (device           file-system-device) ; string | <uuid> | <file-system-label>
+  (device           file-system-device) ; <uuid> | <file-system-label>
+                                        ; <nfs-share> | string
   (mount-point      file-system-mount-point)      ; string
   (type             file-system-type)             ; string
   (flags            file-system-flags             ; list of symbols
@@ -134,6 +139,27 @@
                             (format port "#<file-system-label ~s>"
                                     (file-system-label->string obj))))
 
+;; An nfs-share for use in the 'device' field.
+(define-record-type <nfs-share>
+  (make-nfs-share share)
+  nfs-share?
+  (share nfs-share->string))
+
+(define* (nfs-share share #:key (on-error
+                                  (lambda (share)
+                                    (error "The nfs-share is missing \":/\" in"
+                                           share))))
+  "Try to construct an nfs-share, return (on-errer share) if share is invalid.
+Use #:on-error (const #f)' to check validity and avoid an error to be thrown."
+  (if (string-contains share ":/")
+      (make-nfs-share share)
+      (on-error share)))
+
+(set-record-type-printer! <nfs-share>
+                          (lambda (obj port)
+                            (format port "#<nfs-share ~s>"
+                                    (nfs-share->string obj))))
+
 (define-syntax report-deprecation
   (lambda (s)
     "Report the use of the now-deprecated 'title' field."
@@ -149,7 +175,7 @@
                  file line column)
          #t)))))
 
-;; Helper for 'process-file-system-declaration'.
+;; Helper for the deprecated 'process-file-system-declaration'.
 (define-syntax device-expression
   (syntax-rules (quote label uuid device)
     ((_ (quote label) dev)
@@ -257,6 +283,8 @@ UUID-TYPE, a symbol such as 'dce or 'iso9660."
      (if uuid-type
          (uuid->string (uuid-bytevector device) uuid-type)
          (uuid->string device)))
+    ((? nfs-share?)
+     (nfs-share->string device))
     ((? string?)
      device)))
 
@@ -303,6 +331,8 @@ initrd code."
                   `(uuid ,(uuid-type device) ,(uuid-bytevector device)))
                  ((file-system-label? device)
                   `(file-system-label ,(file-system-label->string device)))
+                 ((nfs-share? device)
+                  `(nfs-share ,(nfs-share->string device)))
                  (else device))
            mount-point type flags options check?))))
 
@@ -316,6 +346,8 @@ initrd code."
                   (bytevector->uuid bv type))
                  (('file-system-label (? string? label))
                   (file-system-label label))
+                 (('nfs-share (? string? share))
+                  (nfs-share share))
                  (_
                   device)))
        (mount-point mount-point) (type type)
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 3d7aa77cb7..27b324deac 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -497,12 +497,15 @@ list of services."
       ;;   root device: UUID: 12345-678
       ;; or:
       ;;   root device: label: "my-root"
+      ;; or:
+      ;;  root device: nfs-share: 0.0.0.0:/my-root
       ;; or just:
       ;;   root device: /dev/sda3
-      (format #t (G_ "  root device: ~[UUID: ~a~;label: ~s~;~a~]~%")
+      (format #t (G_ "  root device: ~[UUID: ~a~;label: ~s~;nfs-share: 
~a~;~a~]~%")
               (cond ((uuid? root-device) 0)
                     ((file-system-label? root-device) 1)
-                    (else 2))
+                    ((nfs-share? root-device) 2)
+                    (else 3))
               (file-system-device->string root-device))
 
       (format #t (G_ "  kernel: ~a~%") kernel)
@@ -649,6 +652,8 @@ checking this by themselves in their 'check' procedure."
       (match device
         ((? string?)
          device)
+        ((? nfs-share?)
+         (nfs-share->string device))
         ((? uuid?)
          (find-partition-by-uuid device))
         ((? file-system-label?)
-- 
2.26.0