Description of problem: mosquitto cannot accept more than 1014 clients on its default configuration. When trying to register more, it'll complain: # journalctl -f -u mosquitto . . . Oct 06 15:17:12 F.Q.D.N mosquitto[47597]: 1665069432: Unable to accept new connection, system socket count has been exceeded. Try increasing "ulimit -n" or equivalent. Version-Release number of selected component (if applicable): Satellite 6.12.0 Snap 13 How reproducible: Always Steps to Reproduce: 1. Configure Satellite or capsule to use MQTT broker 2. Start registering systems against it 3. Wait until reaching 1015 Actual results: Unable to accept new connection, system socket count has been exceeded. Try increasing "ulimit -n" or equivalent. Expected results: New client connected from $CLIENT_IP:$HIGH_PORT as $UUID (p2, c1, k30, u'$UUID'). Additional info: I'm solving it with this: cat /etc/systemd/system/mosquitto.service.d/limits.conf [Service] LimitNOFILE=10000 I've chosen 10000 because it's the "maximum number of clients" for a default Satellite installation according to the tuning guide.
In https://github.com/theforeman/foreman-documentation/pull/1747 I was pointed to this issue. I've opened https://github.com/eclipse/mosquitto/issues/2674 for a long term solution.