I often hear the complaint that people can't give us the log messages "because the container failed and therefore is no more". This is not a problem, however. You can copy any file from a stopped Docker container using scp/rsync syntax:
docker cp <container>:<path> <local-path>
For instance:
$ docker cp 1fbe7cbe61ef:/var/log/um-entrypoint.1601639207.log /tmp
For the system out log, you can get the system out log of started and
stopped containers alike with docker logs <container>
.
Happy reporting!