Fixes a regression introduced in bab6434f58
whereby following the example from the manual regarding non-volatile images
would no longer work.
* gnu/services/virtualization.scm (hurd-vm-shepherd-service): Pass ‘image’ to
‘system-image’ only if it’s an image.
* doc/guix.texi (Virtualization Services): Explicitly say that the ‘image’
field can contain a file name. Remove use of ‘const’ for the ‘image’ field in
persistent image example and adjust text.
Fixes: guix/guix#4130
Reported-by: Maxim Cournoyer <maxim@guixotic.coop>
Change-Id: I1a81ce27fb45978a681310b8a8788ab671b3edf8
d4e06997e4