https://bugzilla.redhat.com/show_bug.cgi?id=1192848
Martin Sivák msivak@redhat.com changed:
What |Removed |Added ---------------------------------------------------------------------------- Status|CLOSED |ASSIGNED Resolution|NOTABUG |--- Keywords| |Reopened
--- Comment #7 from Martin Sivák msivak@redhat.com --- There is one use case you are missing here. A docker.service configured to autostart via systemd while making sure the docker.socket is in place early.
This is needed for containers that mount /var/run/docker.sock and use it to discover other running containers. See for example docker-gen or its usage in https://github.com/jwilder/nginx-proxy
Docker has the annoying habit of creating /var/run/docker.sock/ directory when mounting the socket before it is created as it assumes a new host directory is to be mounted as a volume. This can prevent docker service from starting when combined with autostart containers. It is also almost impossible to fix as docker tools do not work (no daemon is running) and the daemon can't be started (because the directory is created during container autostart = before the proper socket device).
Socket activation (pre-allocation) solves this nicely as the socket file is already present during the container autostart.