Focused, hands-on DevOps and server-side problems with hints, feedback, and automated solution checks.
A daemon exposes a Unix domain socket that every local user can talk to. Protect it so that only root and members of a dedicated group may connect - the same way Docker restricts access to /var/run/docker.sock.
Configure systemd to keep a Unix domain socket open at all times while starting the backing service process only when the first connection arrives.
Make a single echo server listen on either a TCP socket or a Unix domain socket, selected by its command-line argument. The challenge illustrates that the same stream-socket workflow works with two address families (AF_INET and AF_UNIX).
