Mount cgroupv2 for cilium at a custom location

[olemarkus]

This should fix cilium for AL2 5.10 kernel.

[olemarkus]

/cc @rifelpet

[rifelpet]

The cilium's DaemonSet is OnDelete but there's still a chance that between update cluster --yes and all nodes being replaced that a cilium-agent pod being deleted results in it using the new mount path, even though the systemd unit was never ran on that node. Is that a problem we need to address here?

[olemarkus]

In this case, cilium will mount cgroupv2 inside the pod, which works fine. The reason for mounting cgroup2 on the host is to preserve some socket loadbalancing state, which is not that critical.

[rifelpet]

/lgtm
/cc @hakman

[hakman]

/lgtm

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[avdhoot]

This might fixes cilium in flatcar Linux stable (2983.2.0). by default, flatcar mount cgroup2 on /sys/fs/cgroup . Currently, cilium does work with flatcar with kops 1.21.1. I have changed the mount path cilium-cgroup in cilium DaemonSet to /sys/fs/cgroup to make it work.

cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,seclabel)

Is there any chance this can be cherry-picked in kops 1.21.2 @olemarkus

[olemarkus]

The change is unfortunately a bit too big for 1.21 branch, I think. I already had to fix one bug introduced by this change.