[bug#28399] [PATCH 1/2] services: mysql: Fix missing modules on activation.

[ludo@gnu.org (Ludovic Courtès)]

Heya,

Christopher Baines <mail@cbaines.net> skribis:

> On Wed, 20 Sep 2017 11:21:51 +0200
> ludo@gnu.org (Ludovic Courtès) wrote:
>
>> As you can see,
>> /gnu/store/9whwwppmb2sjfsy0967s627bzgdfl8bc-guile-static-stripped-2.2.2/share/guile/2.2,
>> which is at the tail of %load-path, is missing from the root file
>> system, hence the failure.
>> 
>> To work around it, we’d have to either ensure that
>> ‘guile-static-stripped’ is on the root file system, or adjust the load
>> path when we switch roots, or (simplest solution) pre-load (ice-9
>> popen) before ‘switch-root’.
>> 
>> To be continued…
>
> Awesome investigation Ludo. This explanation could match what I was
> experiencing when using the mysql service on GuixSD. Sometimes after
> running guix gc, the system wouldn't boot. This could have been because
> the guile package needed by the initrd was removed from the store.
>
> Given that the initrd has a dependency on this guile, but it doesn't
> reference it because its compressed,

It’s not just that: the initrd embeds a self-contained store; it does
not contain references to the “outer” store.

> how about adding a explicit reference to the guile used? I've attached
> a patch, and this looks to fix the issue as far as the mysql service
> is concerned.

[…]

> From f313f80407039efb215c18de99ee36696528e98a Mon Sep 17 00:00:00 2001
> From: Christopher Baines <mail@cbaines.net>
> Date: Sun, 8 Oct 2017 09:52:24 +0100
> Subject: [PATCH] linux-initrd: Ensure that the guile used in the initrd
>  referenced.
>
> By referencing guile from the initrd, it will be present in the store when
> this initrd is used. If the exact guile used within the initrd isn't present
> in the store, then after root is switched during the boot process, loading
> modules (such as (ice-9 popen)) won't work.
>
> * gnu/system/linux-initrd.scm (expression->initrd)[builder]: Write out a file
>   called references in to the initrd derivation, which includes the store path
>   for guile.

[...]

> +          ;; Due to the compression, the references to the dependencies are
> +          ;; obscured, so write them out uncompressed to a file.
> +          (call-with-output-file (string-append #$ output "/references")
> +            (lambda (port)
> +              (map (lambda (reference)
> +                     (simple-format port "~A\n" reference))
> +                   (list
> +                    ;; The guile used in the initrd must be present in the
> +                    ;; store, so that module loading works once the root is
> +                    ;; switched.
> +                    #$guile))))

That’s very smart!

I think you can remove ‘map’ here since Guile will probably be the only
thing we want to refer to.

Make sure to refer to this bug in the commit message and in the comment.

OK to push with these changes, thank you!

Ludo’.