Troubleshooting some frequent problems with Docker.
A dependency job for docker.service failed (on etna)
Problem: cannot start docker.dock service (we don't yet understand why).
Workaround: sudo dockerd (followed by Ctrl+Z and bg)
Cannot write /home/<user>/.docker
Problem: sudo on Machine X != ustica cannot write /home/<user> (different root users on different machines)
Solution 1: Remove /home/<user>/.docker (not sure whether this always works)
Solution 2: sudo docker --config /tmp build -t <name> . (and maybe also for sudo docker run)