Grub Installer error for multipath disk

[Christopher Nalley]

Installing daily focal from Feb 21 2020.

IBM 8284-22A PowerVM 3.1.1.10
Multipath Virtual SCSI drives provided by Shared Storage Pool from VIO 1 & 2

Upon getting to the installing grub boot loader, grub-probe failes with canonical error about unable to find /dev/mapper/mpatha2

Exiting to shell I find:
/dev/mapper/mpatha-part2 , not /dev/mapper/mpatha2

kpartx -a /dev/mapper/mpatha rebuilds the devices

Exit shell,
grub installer completes, system reboots.

After reboot, error:
Gave up waiting for root file system device. Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/mapper/mpatha2 does not exist. Dropping to a shell!

Dropped to shell, ran kpartx -a /dev/mapper/mpatha, exit shell and OS boots up as normal.

There's a confusion between what the OS is looking for and what is getting created from kpartx during udev?

(initramfs) cd /dev/mapper
(initramfs) ls -l
crw------- 1 10, 236 control
lrwxrwxrwx 1 7 mpatha -> ../dm-0
lrwxrwxrwx 1 7 mpatha-part1 -> ../dm-1
lrwxrwxrwx 1 7 mpatha-part2 -> ../dm-2
(initramfs) kpartx -a /dev/mapper/mpatha
(initramfs) ls -l
crw------- 1 10, 236 control
lrwxrwxrwx 1 7 mpatha -> ../dm-0
lrwxrwxrwx 1 7 mpatha1 -> ../dm-1
lrwxrwxrwx 1 7 mpatha2 -> ../dm-2

aixadmin@ubuntu:~$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu Focal Fossa (development branch)"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
aixadmin@ubuntu:~$ uname -a
Linux ubuntu 5.4.0-14-generic #17-Ubuntu SMP Thu Feb 6 22:47:13 UTC 2020 ppc64le ppc64le ppc64le GNU/Linux
aixadmin@ubuntu:~$ date
Tue 25 Feb 2020 11:47:28 AM EST

[Mike Ranweiler (mranweil)]

I tried this on the netboot DI image on a boston (9006-12C) and I got similar results:

     ┌───────┤ [!!] Install the GRUB boot loader on a hard disk ├────────┐
     │ │
     │ Installation step failed │
     │ An installation step failed. You can try to run the failing item │
     │ again from the menu, or skip it and choose something else. The │
     │ failing step is: Install the GRUB boot loader on a hard disk │
     │ │
     │ <Continue> │
     │

~ # ls -lh /dev/mapper/mpatha*
lrwxrwxrwx 1 root root 7 Mar 14 00:01 /dev/mapper/mpatha -> ../dm-0
lrwxrwxrwx 1 root root 8 Mar 14 00:01 /dev/mapper/mpatha-part1 -> ../dm-85
lrwxrwxrwx 1 root root 8 Mar 14 00:01 /dev/mapper/mpatha-part2 -> ../dm-86
<snip>

I wasn't able to recover it the same way, though, which may be another issue (it has quite a lot of I/O attached). I will try the ubiquity installer on it, too.

[Andrew Cloke (andrew-cloke)]

Marking as "incomplete" while waiting for test results from a multipath system when using the subiquity installer.

[Frank Heimes (fheimes)]

Tests showed that this problem (grub install) does not happen with the live-server image, which is the default image for 20.04 and includes a new installer (subiquity instead of d-i - we now started to flag d-i as legacy).
The image is available here: http://cdimage.ubuntu.com/ubuntu/releases/20.04/release/
If you are prompted to update the installer, when you started the installation at the 2nd screen (after you selected the language), it's recommended to do so to benefit from the latest version with latest fixes.
I'm closing this ticket now - in case you will run into other problems, please open a separate LP bug. Thx