This is a short heads-up for users running their mailcow instance on Ubuntu 18.04: Do NOT upgrade to kernel 4.15.0-
Based on various user reports and more extensive testing this specific kernel release triggers a kernel panic and crashes your server. So far we have been able to figure out, this is related when setting a nameserver in the docker-compose.yml file explicitly (which isn’t new in our code). For some strange reason this commit/hotfix fixes the crashes so far.
You can track the progress for this issue here. However please keep in mind that this is a small warning for our Ubuntu users, as there’s currently no final fix available yet. We’ve also filed a Ubuntu bug report already.
Update on 5th September: The issue was confirmed as a valid kernel bug and is already fixed by the Ubuntu team, see the Launchpad issue here. However, there’s no ETA when the new kernel update will be released.
Update on 11th September: The new fixed kernel image 4.15.0-62.69 was released on 9th September.