LXC fails to start container on some arm64 devices

[Alexander Martinz]

Package version: 1:4.0.6-0ubuntu1~20.04.1

$> lsb_release -rd
Description: Ubuntu 20.04.3 LTS
Release: 20.04

$> uname -a
Linux ubuntu 4.9.295 #5 SMP PREEMPT Thu Jan 20 18:40:42 CET 2022 aarch64 aarch64 aarch64 GNU/Linux

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LXC fails to start containers in Focal 20.04 on some arm64 devices running a kernel version older than 5.4.

The LXC version packaged in Focal is 4.0.6 and makes use of "pidfd".
However, this requires kernel version 5.4+.

There is a check in place, if "pidfd" is usable or not.
Though this check fails for arm64, which results in failing to start containers.

This issue was fixed in 4.0.7 with the following commit:
https://github.com/lxc/lxc/commit/c07b6837e30b8d969060ce7d3f95a30abec637de

Recompiling the focal lxc package with above commit applied fixes this issue and containers start properly again on the affected device.

Upgrading the kernel to fix the affected devices is unfortunately not feasable, because they are running a vendor specific kernel.

Would it be possible to include the fix in a SRU for Focal?

[Alexander Martinz (amartinz)]

This can be closed now because of https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1959993

Thank you very much!