Re: Grub, sparc64, and compressed kernels

[John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>]

On 07/03/2018 09:24 PM, Chris Ross wrote:
> Okay.  So, in prepping a chroot'd md/zfs environemnt on this machine, while
> updating the kernel packages, I see:
> 
> /etc/kernel/postinst.d/zz-update-grub:
> Generating grub configuration file ...
> Found linux image: /boot/vmlinuz-4.16.0-2-sparc64-smp
> Found initrd image: /boot/initrd.img-4.16.0-2-sparc64-smp
> /usr/sbin/grub-probe: error: disk `md0' not found.
> /usr/sbin/grub-probe: error: disk `md0' not found.
> /usr/sbin/grub-probe: error: disk `md0' not found.
> Found linux image: /boot/vmlinuz-4.16.0-1-sparc64-smp
> Found initrd image: /boot/initrd.img-4.16.0-1-sparc64-smp
> /usr/sbin/grub-probe: error: disk `md0' not found.
> /usr/sbin/grub-probe: error: disk `md0' not found.
> Found Debian GNU/Linux buster/sid on /dev/sdd2
> done
> 
> This leads me to the same problem I had earlier, grub (grub-probe or
> grub-install) saying "error: disk `md0' not found."  I think this is why
> I started down a path of looking for an alternative grub2.

Well, you need to tell GRUB to install on the individual disks
and not on the RAID (md0), this won't work - with any boot loader.

> Googling for this error leads me to many people that had had this error,
> sometimes an old double-free problem that isn't hitting me,
> and problems with one-disk md RAID arrays, which isn't my issue.  But I
> don't see anyone with a solution to my problem without the others.  I
> fear I just don't know what I'm looking for.

What double-free problem? That would indicate a software bug, but
this isn't a bug. You just need to tell GRUB not to use md0 as the
target block device as GRUB won't be able to map this to actual
physical disks.

> If anyone else is more familiar with using grub, and has any idea
> how to work around this current situation, I'd appreciate a pointer.
> 
> (chroot) root@t5120# grub-install --force --skip-fs-probe /dev/md0 
> Installing for sparc64-ieee1275 platform.
> grub-install: error: disk `md0' not found.
> (chroot) root@t5120# ls -l /dev/md*
> brw-rw---- 1 root disk  9,  0 Jul  3 14:26 /dev/md0
> crw------- 1 root root 10, 62 Jul  3 12:19 /dev/mdesc
> (chroot) root@t5120# df /boot
> Filesystem     1K-blocks  Used Available Use% Mounted on
> /dev/md0          458396 63776    366432  15% /boot
> (chroot) root@t5120# 

Don't use /dev/md0, use /dev/sd* and install on any of the disks that
are part of the RAID. You cannot boot from /dev/md0 as the kernel needs
to be running to be able to access the software RAID device.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913