bug#44353: [PATCH version-1.2.0 v2] guix: system: Add a new '--non-volatile' option for disk-image.

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hello,

Ludovic Courtès <ludo@gnu.org> writes:

> Hi Maxim,
>
> Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis:
>
>> * guix/scripts/system.scm (%options)[volatile-root?]: New boolean option.
>> (%default-options): Set its default value to #f.
>> (show-help): Add help doc.
>> * guix/scripts/system.scm (perform-action): Propagate option...
>> (system-derivation-for-action): ...here.  Use it to set the volatile-root?
>> field of the image object passed to SYSTEM-IMAGE.
>> * doc/guix.texi (Invoking guix system): Document it.
>
> Due notably to the “string freeze”, I think we shouldn’t apply it to
> ‘version-1.2.0’.
>
> Some comments:
>
>> +@code{disk-image}.  By default, the root file system of a disk image is
>> +mounted volatile; the @option{--non-volatile} option can be used to make
>
> That’s not generally the case, though in (gnu system image), only two
> image types have it set to false.

Note that the only two images with volatile-root? #f are ARM, and not by
intent but as a workaround:

   ;; FIXME: Deleting and creating "/var/run" and "/tmp" on the overlayfs
   ;; fails.

> Before the new image API though, ‘disk-image’ did not produce a volatile
> root, IIRC.  I’m tempted to think that we should set (volatile-root?
> #f) on image types where it makes sense, which is maybe all of them
> except ISO.  (Then we need to make sure ‘guix system vm’ still gets a
> volatile root.)
>
> WDYT, Mathieu?

Based on your comments and those of Mathieut, I've made volatile-root?
#f the default for 'guix system disk-image', with a '--volatile' option
to maintain the ability to have the rootfs mounted volatile, and
adjusted the doc accordingly.

> So apart from the sentence above, the patch LGTM for ‘master’!

Thanks for the review!

Maxim