On Wed, Mar 03, 2021 at 10:28:34AM -0500, Marc Auslander wrote:
> One potential gotcha. When you boot from an mdadm file system containing
> /boot/grub, grub will not write to the file system. In particular, it will
> not update grub/grubenv even if you have a save_env line in grub.cfg. So if
> you use grub-reboot to specify an alternate line in grub.cfg, you need to
> reset grubenv afterwards. I do this in a root @reboot cron job.
>
> If you don't know what I'm talking about, you probably don't need to worry
> about this.
I don't *know* know what you're talking about, but I think I get the
gist of it. I'm not doing anything fancy enough to have to deal with
the details of grubenv and grub-reboot, but your initial comment about
grub refusing to write to a mdadm filesystem is consistent with what I
was seeing, and it's nice to have confirmation that it actually does
work that way.
Dave the issues you describe dealing with mdadm setup, well that's why I eventually
just switched to LVM-based mirroring and striping. Early on, LVM wasn't supported as a boot
volume, but the original code base had supported that on HP-UX and AIX. So years ago now,
that restriction was lifted. Another mdadm issue is just the use of it in a kind of
"oral tradition": it's not that setup is hard, it just still seems like magic spells after all this time.
--
Dave Sherohman