Rogue docker processes on Ubuntu: Snap!

I’ve come across a situation where out of three docker containers that should be running, only one was shown by docker container ls -a. Weird, hu?

The missing two were clearly running their processes because the web service they provided was active and reachable.

After a lot of forth and back, it turned out that Ubuntu 20.04 with snap came with a docker snap – and had a recent Docker CE installed via the apt package manager. Don’t do that.

Once the snap docker was removed, it worked and showed all the containers again.