Update 2026: this setup has since been upgraded to Redmine 6.1 on PostgreSQL 15, and the permission workaround below is no longer needed. See Upgrading a neglected Redmine: PostgreSQL 9.6 → 15 and Redmine 5.0 → 6.1 in Docker.
I had an old Redmine backup from 2017 lying around and wanted it running again on a current system. This is a quick record of how I restored it with the sameersbn Docker images, and the permission problem that kept getting in the way.