How to change the "mysql" user's uid and gid (permanently) inside a rootful container?

[ojde]

Unfortunately the user mysql inside the container uses uid:gid 27:27. On the host system gid 27 is the sudo group and a user uid 27 does not exist, so e.g. lsof complaines about ownership and processes of a 27 not being in passwd.

I've made various attempts with --uidmap --gidmap, --userns=, even with usermod inside the container but got either the container just not starting at all anymore (no output in any logs) or permission denied on mounting storage (which I always chowned!).

Any hint would be appreciated.