[PVE-User] zfs root after last update grub unknown filesystem

[Gianni Milo]

UEFI boot mode is indeed a good option, as it does not rely on the ZFS pool
for booting the system (it uses a separate VFAT partition for the
bootloader).
However, this method does not solve another problem which is the redundancy
of the bootloader, as the UEFI partition can be installed only on a single
(boot) drive. If that drive fails, then one must rebuild the UEFI partition
on a different or on the replacement drive.

On Mon, 14 Sep 2020 at 09:14, Arjen via pve-user <pve-user at lists.proxmox.com>
wrote:

>
>
>
> ---------- Forwarded message ----------
> From: Arjen <leesteken at protonmail.ch>
> To: Proxmox VE user list <pve-user at lists.proxmox.com>
> Cc:
> Bcc:
> Date: Mon, 14 Sep 2020 08:04:03 +0000
> Subject: Re: [PVE-User] zfs root after last update grub unknown filesystem
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Monday, September 14, 2020 9:07 AM, Aaron Lauterer <
> a.lauterer at proxmox.com> wrote:
>
> > Alternatively you can try to install the machine in UEFI mode. In UEFI
> mode with root ZFS the installer will set up systemd-boot instead of grub.
> This alleviates the problem with grubs limited ZFS compatibility.
> >
> > See the docs for more infos:
> https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysboot
> >
> > HTH,
> > Aaron
>
> I had the same problem with a zpool feature that could not be turned off.
> I used this work-around for a while in the hope that the bug would be fixed
> (GRUB patch existed for 5 years but it was never tested/reviewed):
> Put a new Proxmox VE installation on USB and copy /boot from the hard
> drives to the USB installation.
> With that, it could boot from USB, after which it would pickup on the
> rpool on the hard drives (probably by lucky chance).
> Eventually, reinstalling with UEFI+GPT+ESP+systemd-boot (which did not
> exists when I encountered the issue) fixed it.
>
> I would suggest taking the pain now, and reinstall using UEFI, to prevent
> such issues in the future.
>
> > On 9/14/20 12:16 AM, Gianni Milo wrote:
> >
> > > GRUB does not support all zfs features, so it's quite common for it to
> fail
> > > to recognise the rpool during boot if it has a feature which is
> > > incompatible with it. In your case, I believe that is the "encyption"
> > > feature.
> > > Do you recall the issue starting after enabling encryption on
> rpool/data
> > > dataset? If so, you may have to rebuild the pool and leave rpool/data
> > > unencrypted.
> > > Note that even though you enabled encryption only on rpool/data, the
> > > feature will take effect at the pool level, hence the GRUB issue you
> > > are facing.
> > > Because of this issue, people have started using a separate boot pool
> > > (bpool), with limited zfs features enabled and a different data pool
> > > (rpool) for the OS and the data. I believe that the PVE installer
> should be
> > > modified to follow this approach (if it hasn't done it already) to
> overcome
> > > similar issues.
> > > Gianni
> > > On Sun, 13 Sep 2020 at 22:29, Stephan Leemburg
> sleemburg at it-functions.nl
> > > wrote:
> > >
> > > > Hi All,
> > > > I have a proxmox system at netcup that was clean installed about two
> > > > weeks ago.
> > > > It is full zfs, so root on zfs. I am migrating from one netcup system
> > > > with less storage to this system.
> > > > This system is using the pve-no-subscription repository, but after
> > > > migration I will move the subscription from the 'old' system to this
> > > > system.
> > > > The rpool/data dataset is zfs encrypted.
> > > > Today I did zfs send/recv from the 'old' system to this system to the
> > > > rpool/data dataset.
> > > > After that I did an apt update and noticed there where updates
> available.
> > > > After the upgrade and the mandatory reboot, the system does not come
> up
> > > > anymore. It is stuck in grub rescue.
> > > > Grub mentions that it has a 'unknown filesystem'.
> > > > Has anyone else experienced this same situation?
> > > > If so and you could recover, what was the reason and fix?
> > > > I am still researching what is causing this. If I boot a .iso then I
> can
> > > > import the pool and see all datasets and subvolumes.
> > > > So, it seems that the zpool itself and the datasets are ok, it is
> just
> > > > that grub is unable to recognize them for some reason.
> > > > I have read about other situations like this where large_dnode
> seemed to
> > > > be the cause. I noticed that on the zpool large_dnode is enabled.
> And it
> > > > is a creation only setting. It cannot be changed to disabled
> afterwards.
> > > > This must have been done by the Proxmox installer. As booting is
> about
> > > > the root filesystem, I guess the zfs send / recv to the rpool/data
> > > > dataset would have nothing to do with it, but I could be wrong.
> > > > I will continue my research tomorrow evening after some other
> > > > obligations, but if anyone has an idea, please share it. If it is
> just
> > > > how to get more debugging info out of the zfs module in grub.
> > > > Because 'unknown filesystem', with the zfs module loaded is kind of
> not
> > > > helping enough..
> > > > Best regards,
> > > > Stephan
> > > >
> > > > pve-user mailing list
> > > > pve-user at lists.proxmox.com
> > > > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
> > >
> > > pve-user mailing list
> > > pve-user at lists.proxmox.com
> > > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
> >
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> > pve-user at lists.proxmox.com
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>
>
>
>
>
>
> ---------- Forwarded message ----------
> From: Arjen via pve-user <pve-user at lists.proxmox.com>
> To: Proxmox VE user list <pve-user at lists.proxmox.com>
> Cc: Arjen <leesteken at protonmail.ch>
> Bcc:
> Date: Mon, 14 Sep 2020 08:04:03 +0000
> Subject: Re: [PVE-User] zfs root after last update grub unknown filesystem
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