2 files changed, 13 insertions(+), 6 deletions(-)

M doc/guix.texi
M gnu/services/virtualization.scm

@@ 40911,6 40911,10 @@ The image type name.  Use @code{'hurd-qcow2} for a 32-bit image or
 The image object representing the disk image of this virtual machine
 (@pxref{System Images}).
 
+Alternatively, this can be the file name (a string) of an image, which
+is useful if you want the image to persist across service restarts---see
+example below.
+
 @item @code{disk-size} (default: @code{'guess})
 The size of the disk image.
 


@@ 41009,15 41013,16 @@ with the following non-volatile secrets, unless they already exist:
 @end table
 @end deftp
 
-Note that by default the VM image is volatile, i.e., once stopped the
-contents are lost.  If you want a stateful image instead, override the
-configuration's @code{image} and @code{options} without
-the @code{--snapshot} flag using something along these lines:
+Note that by default the VM image is volatile---i.e., once the service
+is stopped, the contents are lost.  If you want a persistent image
+instead, override the configuration's @code{image} and @code{options}
+without the @option{--snapshot} flag using something along these lines:
 
 @lisp
 (service hurd-vm-service-type
          (hurd-vm-configuration
-          (image   (const "/out/of/store/writable/hurd.img"))
+          ;; Specify an out-of-store, persistent image.
+          (image "/out/of/store/writable/hurd.img")
           (options '())))
 @end lisp
 

@@ 1904,7 1904,9 @@ is added to the OS specified in CONFIG."
                              '())
                       #$@net-options
                       #$@options
-                      "--hda" #+(system-image image)
+                      "--hda" #+(if (image? image)
+                                    (system-image image)
+                                    image)
 
                       ;; Cause the service to be respawned if the guest
                       ;; reboots (it can reboot for instance if it did not