IBM Z DPM Partitions require a /boot partition when using LVM/RAID
Affects | Status | Importance | Assigned to | Milestone | ||
---|---|---|---|---|---|---|
MAAS | Status tracked in 3.6 | |||||
3.4 |
Won't Fix
|
Low
|
Unassigned | |||
3.5 |
Won't Fix
|
Low
|
Unassigned | |||
3.6 |
Triaged
|
Low
|
Unassigned | |||
Ubuntu on IBM z Systems |
Triaged
|
Medium
|
Unassigned |
Bug Description
On IBM Z DPM Partitions the HMC firmware loads the kernel and initrd from the storage volume. This supports various filesystems but does not support RAID/LVM. To use RAID/LVM you need to keep the kernel and initrd on a separate /boot partition so the HMC can load the kernel and initrd. Then the Linux kernel can mount the RAID/LVM volume.
RAID and LVM fail in different ways. When RAID is used Curtin successfully finishes but the partition goes into a terminated state as it doesn't know how mount an mdraid block device. LVM actually causes Curtin to fail
Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmphkwow1
update-initramfs: Generating /boot/initrd.
Error: Unsupported setup: Directory '/boot' is located on a multi-target device-mapper device
Error: Script could not determine target parameters
Using config file '/etc/zipl.conf'
Run /lib/s390-
run-parts: /etc/initramfs/
Running command ['udevadm', 'settle'] with allowed return codes [0] (capture=False)
TIMED subp(['udevadm', 'settle']): 0.028
Running command ['umount', '/tmp/tmphkwow1
Running command ['umount', '/tmp/tmphkwow1
Running command ['umount', '/tmp/tmphkwow1
Running command ['umount', '/tmp/tmphkwow1
finish: cmd-install/
finish: cmd-install/
I suspect this is a bit of an edge case as IBM Z volumes are multipath. This provides the redundancy of RAID and the flexibility of LVM.
tags: | added: s390x |
Changed in maas: | |
status: | New → Triaged |
importance: | Undecided → Medium |
Changed in ubuntu-z-systems: | |
status: | New → Triaged |
importance: | Undecided → Medium |
Changed in maas: | |
milestone: | 3.4.0 → 3.4.x |
Changed in maas: | |
milestone: | 3.4.x → 3.5.x |
I think it's good (not to say 'best') practice to have a separate /boot partition in LVM environments (even if s390x should support booting from /boot as part of a LVM with linear mapping).
A separate /boot outside the LVM is also the partition scheme that is used by subiquity (and d-i) in case of LVM installations.
And especially on server systems it's more robust to have a separate /boot in case of boot problems occure, since troubleshooting and fixing is easier.
See also LP 1680101.