21.10 Impish ZFS revert snapshot via grub menu fails consistently

[Nicholas Harvey]

This issue seems similar to 1894329 but I can reproduce this consistently in 21.10.

Problem description:
Unable to reliably revert ZFS snapshots via the Grub menu in Ubuntu 21.10. When attempting a revert I am usually dropped to the emergency mode and have to force a reboot. After that it can take a number of attempts to get the system to reboot to the desktop.

Steps to reproduce:
Install Ubuntu 21.10 on Intel 64bit with ZFS selected as the filesystem. Do not encrypt.
Install all updates. ZFS snapshot is taken automatically.
Reboot.
Install a simple package i.e. sudo apt install neofetch. Another ZFS snapshot is taken automatically.
Reboot and enter the GRUB menu.
Enter History menu.
Select Revert to an earlier snapshot. In my case I select the snapshot taken before neofetch was installed.
Select install system files only. Do not select the recovery mode option.
System now boots and ends up dropping into emergency mode.

I can duplicate this on three different installs.

Expected outcome:
The snapshot is correctly reverted and the system boots without user interaction into the snapshot.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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[Nicholas Harvey (mobile-harvey)]

Rough guess this relates to the zfs-Linux package.

[Nicholas Harvey (mobile-harvey)]

Just spun-up a couple of Gnome Boxes to test this. 21.10 fails as per my description whereas 20.04.03 LTS works fine. Just to be clear I am selecting to revert the snapshot at the top of the list each time (this is the snapshot taken just before neofetch is installed).

Meanwhile my main laptop where I first experienced this problem no longer boots and so I am re-installing with the LTS, so for me this is a nasty issue. I do have another test machine and am happy to collect data if required but as I say this can easily be duplicated.

Thanks
Nick

[Timo Aaltonen (tjaalton)]

seeing the same here after upgrade to jammy broke mounting natively encrypted rpool

[Nicholas Harvey (mobile-harvey)]

As described in bug 1946808 I have enabled impish-proposed updates, applied all updates, and rebooted. I then sudo apt purge neofetch to create a testable ZFS snapshot and reboot.

I am now able to successfully roll-back this change vat the ZFS snapshot using the GRUB history menu, and so it appears for my tests at least that the proposed update solves this.

Nice one!

Thanks
Nick