ZFS installation on Raspberry Pi is problematic

[andrum99]

Version: Ubuntu Server 20.04 - preinstalled 64-bit image for Raspberry Pi.

ZFS on the Pi under 20.04 is currently a bit problematic. Upon issuing the command 'zpool status', I'm helpfully directed to install zfsutils-linux. When I do this, it complains that it cannot find the ZFS module, then errors out. Worse than that, the zfsutils-linux package does not depend on the zfs-dkms package, so it doesn't attempt to build the ZFS kernel modules automatically.

The workaround is to install zfs-dkms, which builds the required kernel modules. (Once this has been done, the usual errors when installing the zfsutils-linux package, caused by there being no ZFS pools on the system, can be worked around by creating a zpool, then rerunning 'sudo apt install zfsutils-linux', as with previous versions of Ubuntu and Debian).

I have not tested on other hardware platforms - this problem may also exist on other platforms where the user has not selected to install to ZFS.

I have selected 'zfsutils' as the affected package, which is not the name of an actual current package, since launchpad won't let me submit the bug without selecting a package, however it's not clear to me that the problem is caused by that package.

[Hans Joachim Desserud (hjd)]

Looks like `zfsutils-linux` is part of the source package `zfs-linux`

[Andreas Hasenack (ahasenack)]

Adding zfs to the pi kernel was discussed and rejected in the past: https://bugs.launchpad.net/ubuntu/+source/linux-raspi2/+bug/1852119

[andrum99 (andrum99)]

Just to clarify: I'm not suggesting ZFS be included by default on the Raspberry Pi. I'm saying that it should be possible to install ZFS on the Raspberry Pi without jumping through so many hoops. I appreciate this is a tricky one though, since presumably there are other arm64 platforms that have more RAM. Perhaps a note in the release notes about the required workaround, i.e. manually install zfs-dkms using apt? (In 19.10 it was a dependency of zfsutils-linux).

[satmandu (satadru-umich)]

Maybe it makes sense to create a virtual package dependency which can pull in zfs-dkms for the non-arm64 architectures which get zfsutils-linux installed?

For instance aufs-dkms is a virtual package which is satisfied by the official kernel packages.

[Richard Laager (rlaager)]

I think it used to be the case that zfsutils-linux depended on zfs-dkms which was then provided by the kernel packages. That seems like a way to solve this. Given that dkms is for dynamic kernel modules, it was always a bit weird to see the kernel providing that. It should probably be that zfsutils-linux depends on zfs-dkms | zfs-module, and then the kernel provides zfs-module.

[andrum99 (andrum99)]

If this can be fixed by tweaking package dependencies, without negatively affecting other platforms, then that would be ideal 👍

[Colin Ian King (colin-king)]

Just for the heads-up, I've evaluated ZFS on a range of raspberry Pis now and recommended we enable ZFS as part of the kernel package build. I can't promise when this will land but it will remove this problem in the long term.

[andrum99 (andrum99)]

Thanks for the heads up. The package dependencies should probably be fixed as well. Glad to hear you've now qualified zfs on Pi - it's worked fine for my limited use, so it gives me more confidence that I'm not going to run into trouble if I start stressing the box a bit more.

[satmandu (satadru-umich)]

This suggested policy change is welcome. As per https://bugs.launchpad.net/ubuntu/+source/linux-raspi2/+bug/1852119/comments/2 the argument was that the RPI4 only has 4Gb of ram.

"we do not support ZFS unless you have at least 4GB of memory free.

Today the 8Gb RPI4 was announced.

https://www.raspberrypi.org/blog/8gb-raspberry-pi-4-on-sale-now-at-75/

I'm no expert, but I suspect that this device will be able to handle 4GB of memory free with ease...

[Colin Ian King (colin-king)]

Indeed, I've already testing this on 8GB and 4GB devices, so it's on the TODO list for the raspi kernels.

[Stéphane Graber (stgraber)]

Good to hear. I just ran into this today when working on a LXD appliance based on Ubuntu Core.
btrfs isn't exactly great as an alternative and the 8GB Pi is definitely ZFS capable so would be great to have :)

[Juerg Haefliger (juergh)]

https://lists.ubuntu.com/archives/kernel-team/2020-June/111366.html

[Colin Ian King (colin-king)]

Thanks Juerg. Can you close this bug once it lands?

[Juerg Haefliger (juergh)]

ZFS now comes pre-built for arm64 with kernel linux-raspi 5.4.0-1015.15 which is in -updates.

[andrum99 (andrum99)]

Thanks for adding the ZFS module for Pi 😁