Comment # 4 on bug 1156441 from Ignaz Forster

(In reply to Michael Chang from comment #3)
> (In reply to Fabian Vogt from comment #2)
> > (In reply to Michael Chang from comment #1)
> > > If I remember correctly Ignaz has a solution to the health_checker_flag
> > > issue by using a writable subvolume in combination of grub script snippet.
> > > Would this be related or we are having other issue ?
> > 
> > It's tangentially related, having grubenv moved below /boot/writable allows
> > initializing env_block even with a read-only /boot. grub2-install isn't
> > called from that context though, so that shouldn't really matter.
> 
> I am confused as this seems to conflict with "grub2-install should take care
> of setting up the env_block for systems ..." from description above. Here
> you are with "grub2-install isn't called from that context though, so that
> shouldn't really matter."

The problem is imho a slightly different one: As long as the 'env_block'
variable is not set it is not possible to write to the environment block from
within GRUB with Btrfs. This means that at least on first boot it isn't
possible to write any value there.

On read-only root file systems we have the additional problem that we obviously
can't force writing the file later (e.g. during first boot), so in the end we
need a mechanism which makes sure grubenv is initialized properly during
installation. At least that's how I understand Fabian's ticket.

(The /boot/writable subvolume doesn't help here, as the env_block is only
written to /boot/grub2/grubenv.)