Systemd checks report issue in Ubuntu image

[snowch]

The Ubuntu image systemd check returns an error, preventing KD appconfig packages from working.

root@kdss-mdz2r-0:/# systemctl status systemd-journald
System has not been booted with systemd as init system (PID 1)

For more info: #415

[kmathur2]

@joel-bluedata are you looking at this already? @Vellanci and I were going to look at this also. Let us know.

[aleshchynskyi]

According to my findings Systemd doesn't work in containers out of box. One way of fixing it is by adding cgroup mount and making it privileged. Another one way is by adding more tmpfs mounts (for /run, /run/lock) and allowing it to be unprivileged. For kubernetes it can implemented by using emptyDir and localPath mounts. Also Dockerfile should install systemd and couple of env vars. I managed to get it working with simple kubernetes pod. I will continue investigation on how to do it with KD.

[kmathur2]

Adding @swamibluedata for visibility

[aleshchynskyi]

I noticed "systemdRequired" that implements the unprivileged way I mentioned before. Apart from mount points created by this feature, for Ubuntu Systemd /run/lock is also required to be mounted. Also current ubuntu image doesn't run systemd as PID 1 (entrypoint) process.

[aleshchynskyi]

I managed to solve the issue with two changes:

1. On KD side generate /run/lock tmpfs volume mount (/run, /tmp is already generated at stateful set creation time).
2. On Ubuntu app side update image to run systemd as entrypoint process.