dmaze@monad:~$ docker images postgres
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
postgres 9.3 7b9abcbfddf1 7 hours ago 482.5 MB
postgres latest 7b9abcbfddf1 7 hours ago 482.5 MB
dmaze@monad:~$ docker run postgres
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.
[...]
Success. You can now start the database server using:
postgres -D /var/lib/postgresql/data
or
pg_ctl -D /var/lib/postgresql/data -l logfile start
FATAL: could not create lock file "/var/run/postgresql/.s.PGSQL.5432.lock": Permission denied
If I log into the container directly, I see the directory /var/run/postgresql/ is mode 2775 owned by root:root, so the postgres:postgres user:group can't actually create a pid file there.