[bug#72803] Add restic commands to the restic-guix package

[Fabio Natali]

Hi Giacomo,

Thanks for the patch and for the Restic service in the first place.

> diff --git a/doc/guix.texi b/doc/guix.texi

In the manual, consider the "extra-flags" section where we say:

> A list of values that are lowered to strings. These will be passed as
> command-line arguments to the current job restic backup invokation.

Perhaps this should now read "...the current job restic invokation..."
or "...the current restic invokation...", as the action is no longer
limited to "backup"?

>      (program-file
> -     "restic-backup-job.scm"
> +     (string-append "restic-" action "-" name "-program.scm")

Should 'name' be slug-ified in any way here? E.g. to avoid spaces,
capital letters, symbols that might be confusing when part of a file
name, etc.

> +  (define action-table
> +    (map
> +     (lambda (action)
> +       (list action
> +             (map (lambda (job)
> +                    (list (restic-backup-job-name job)
> +                          (restic-action-program job action)))
> +                  jobs)))
> +     ;; run is an alias for backup
> +     (filter (lambda (a) (not (string=? a "run"))) supported-actions)))

Could this be (marginally) simpler if we used two nested association
lists? That way, 'get-program' might simply use 'assoc-ref' (twice) and
'assoc-table' would be redundant?

Everything else looks fine to me. For what it's worth, here's how I've
been testing this.

Initialise a Restic repository as follows (warning: this overwrites
'/some-temporary-folder/password'):

--8<---------------cut here---------------start------------->8---
mkdir /some-temporary-folder
export RESTIC_PASSWORD=password
restic init --repo=/some-temporary-folder/repository
echo "${RESTIC_PASSWORD}" > /some-temporary-folder/password
--8<---------------cut here---------------end--------------->8---

Save the following system definition as
'/some-temporary-folder/config.scm'.

--8<---------------cut here---------------start------------->8---
(use-modules (gnu))
(use-package-modules backup)
(use-service-modules backup)

(operating-system
  (host-name "host")
  (bootloader (bootloader-configuration
               (bootloader grub-bootloader)
               (targets '("/dev/vda"))))
  (file-systems (cons (file-system
                        (device "/dev/vda1")
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems))
  (packages (cons* restic %base-packages))
  (services (cons*
             (service restic-backup-service-type
                      (restic-backup-configuration
                       (jobs
                        (list (restic-backup-job
                               (name "test")
                               (repository "/restic/repository")
                               (password-file "/restic/password")
                               (schedule "* * * * *")
                               (files '("/root")))))))
             %base-services)))
--8<---------------cut here---------------end--------------->8---

>From a Guix checkout where this patch has been applied, launch a test VM
as follows:

--8<---------------cut here---------------start------------->8---
$(./pre-inst-env guix system vm \
    --no-graphic \
    --share=/some-temporary-folder=/restic \
    /tmp/config.scm) \
    -m 2048 -smp 2
--8<---------------cut here---------------end--------------->8---

Log in as root, then check that the cron schedule is correctly defined
with 'herd schedule mcron', backup jobs should be scheduled every
minute.

Mount the Restic repository to see that snapshots have been actually
created every minute since boot. This can be done either on the guest or
on the host system. E.g. on the guest:

--8<---------------cut here---------------start------------->8---
restic mount \
    --password-file=/restic/password \
    --repo=/restic/repository \
    /mnt
--8<---------------cut here---------------end--------------->8---

Unfortunately I don't have commit access to push this, but hopefully
someone else will have a second look and push it soon.

It'd be nice to have a little test suite for this, but in case this can
be part of a future patch.

HTH, thanks, Fabio.