Probably caused by people aborting an installation attempt due to https://bugs.launchpad.net/ubuntu/+source/docker.io/+bug/1628053 and then trying again, but by then the group already exists. Just an idea, I haven't debugged it.
Probably caused by people aborting an installation attempt due to https:/ /bugs.launchpad .net/ubuntu/ +source/ docker. io/+bug/ 1628053 and then trying again, but by then the group already exists. Just an idea, I haven't debugged it.