** Also affects: zfs-linux (Ubuntu)
Importance: Undecided
Status: New
** Tags added: foundations-todo
** Changed in: ubuntu-release-upgrader (Ubuntu)
Assignee: (unassigned) => Julian Andres Klode (juliank)
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https://bugs.launchpad.net/bugs/2110891
Title:
System freeze on release upgrade 24.10 oneiric to 25.04 plucky with
root fs on ZFS and snapshots
Status in ubuntu-release-upgrader package in Ubuntu:
Confirmed
Status in zfs-linux package in Ubuntu:
New
Bug description:
SUMMARY:
I'm running Ubuntu 24.10 on a ZFS root fs on LUKS which also has snapshots.
As part of the release upgrade process ubuntu-release-upgrader is triggering a
bug in ZFS triggered by the update-grub steps which executes ls
/.zfs/snapshot/… via 10_linux_zfs and eventually causes a kernel deadlock on
mount.zfs.
As the `ls` statement in question works flawlessly before the upgrade
process, I assume the hang is caused due to ZoL been replaced by apt
previously? That's why I feel this is a ubuntu-release-upgrader
package bug.
I've reported this bug also upstream at ZoL:
https://github.com/openzfs/zfs/issues/17337
DETAILED DESCRIPTION:
I've failed now 7 time to upgrade my Ubuntu 24.10 to 25.04 (Beta, RC, First
Release, Today). In all cases the upgrade runs into a complete system freeze
deadlock. `zfs rollback` for the rescue. Today, only using text console with
screen & running `dmesg -Hxw`, `htop -d 5` and `do-release-upgrade` in parallel
I finally was able to pinpoint the problem:
1. `do-release-upgrade` downloads & install all updated .deb
packages
2. Eventually, the upgrade tries to run `upgrade-grub`
3. The grub script executes the hook `10_linux_zfs` to identify the
available kernel versions for the grub boot menu
4. As part of this discovery an `ls /.zfs/snapshot/[snapshot]/etc`
is executed which causes a system freeze
5. Eventually, after a long pause the kernel reports `task ls:…
blocked for more than 122 seconds.`
6. Only option left for me is to shutdown server and revert to ZFS
snapshot I did before the upgrade
REMARKS:
* Executing "ls /.zfs/snapshot/[snapshot]/etc" and "update-grub" works
successfully BEFORE upgrade
* Rebooting into the partial upgraded system, running "strace update-grub"
reproduces the problem.
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