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

[Aaron Lauterer <a.lauterer@proxmox.com>]

On 9/14/20 11:29 AM, Gianni Milo wrote:
> 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.

Have you read the documentation [0]? Especially chapter 3.11.4?

We added and the pve-efiboot-tool and hooked it into the update-initramfs to keep the EFI partition up to date on each disk used for the root pool so that if one disk fails, you can still boot from one of the remaining ones. The documentation on how to replace a failed boot drive takes into account on how to get the bootloader set up as well.

[0] https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysboot

> 
> On Mon, 14 Sep 2020 at 09:14, Arjen via pve-user <pve-user@lists.proxmox.com>
> wrote:
> 
>>
>>
>>
>> ---------- Forwarded message ----------
>> From: Arjen <leesteken@protonmail.ch>
>> To: Proxmox VE user list <pve-user@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@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@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@lists.proxmox.com
>>>>> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
>>>>
>>>> pve-user mailing list
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>>>
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>>
>>
>>
>>
>>
>>
>> ---------- Forwarded message ----------
>> From: Arjen via pve-user <pve-user@lists.proxmox.com>
>> To: Proxmox VE user list <pve-user@lists.proxmox.com>
>> Cc: Arjen <leesteken@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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