Re: Seeking guidance regarding system roll-back and switch-generation

[Ludovic Courtès]

Hi Chris,

Chris Marusich <address@hidden> skribis:

>> The output of ‘guix system build’ contains the ‘parameters’ file, which
>> is enough to generate grub.cfg (see ‘previous-grub-entries’ in (guix
>> scripts system)).
>
> What if someone specifies extra "menu-entries" in their operating system
> configuration file?  (as described in "(guix) GRUB Configuration")?
> Those extra entries don't appear to be stored in the parameters file.

They’re not stored there, but that’s fine: since there’s only one
grub.cfg, we just store the menu entries that are defined in
‘operating-system’ at the moment ‘guix system reconfigure’ is run.  This
part is “imperative” in nature.

> It would be very convenient if we could just store the entire
> <grub-configuration> in the built system output (e.g., the parameters
> file).  Is that possible?

I don’t think it’s useful because what matters is the
<grub-configuration> that we see in the new operating system.

What do you think?

>> However, the activation script is indeed missing.  We can add it to the
>> output of ‘guix system build’ by extending ‘system-service-type’:

[...]

>> This way we have direct access to each generation’s activation script
>> and we should be fine with (3).
>>
>> WDYT?
>
> I'm afraid I don't yet know enough about gexps and the activation
> process to give an informed opinion on that suggestion.  After I finish
> the first milestone (switch symlinks and rebuild grub.cfg), I'll study
> those topics in more detail and revisit your proposal.

Sure.

Thank you!

Ludo’.