Hi list, please help with a realtime permissions issue trying to start jackd via my systemd service script on raspbian. As root or as user peter (which is part of the audio group) I can start jackd fine using either jackd -v -R -d alsa -r 44100 -P or jackd -v -d alsa -r 44100 -P No error message mention that realtime was (or wasn't) enabled. Is this normal and intended? Checking with htop, there are three jackd processes with a priority of 20 and on with -11. Does this mean that realtime is enabled? Using mplayer as user peter I can play back audio via jack. Now I try to start jackd automatically from a systemd service file created as /etc/systemd/system/jackd.service with the following contents: [Unit] Description=jackd After=sound.target [Service] User=peter ExecStart=/usr/bin/jackd -d alsa -r 44100 -P [Install] WantedBy=multi-user.target I install that service with sudo systemctl enable jackd.service and run sudo systemctl daemon-reload after having changed the above service file. When I start that service it fails with errors in the journal: "JACK is running in realtime mode, but you are not allowed to use realtime scheduling." and "Please check your /etc/security/limits.conf for the following line" and so on. Messages that are not present when starting jackd as user from the command line. Now I am puzzled because I thought that it is enough to specify user "peter" in the systemd service. Well if I comment the line User=peter out and start the service again, jackd runs. It is five processes with priority 20 and one with -11. The stupid thing now is that the normal user peter can use that jackd: Mplayer tells me that "connect(2) call to /tmp/jack-1000/default/jack_0 failed (err=No such file or directory)" So I reckon that a user can't use a jackd started by another user, or root? Now I removed above service and installed it as user service ~/.local/share/systemd/user/jackd.service and contents: [Unit] Description=jackd After=sound.target [Service] User=peter ExecStart=/usr/bin/jackd -d alsa -r 44100 -P [Install] WantedBy=default.target It gets installed with systemctl --user enable jackd.service and started with systemctl --user start jackd.service Jackd is now started and can be used with mplayer. But the systemd service is no longer started at boot not at login of user peter. I have to run: systemctl --user start jackd.service Also trying loginctl enable-linger peter does not help. The general question remains: How can I run a systemd user service without that user being logged in? Another way recommended at https://www.linux.org.ru/forum/admin/10795275 or https://ask.fedoraproject.org/en/question/131584/jack-fluidsynth-as-user-sy… is to add some lines specifying Limits. [Unit] Description=jackd After=sound.target [Service] User=peter LimitRTPRIO=infinity LimitMEMLOCK=infinity ExecStart=/usr/bin/jackd -d alsa -r 44100 -P [Install] WantedBy=multi-user.target It does not start jackd with the same error as above. "JACK is running in realtime mode, but you are not allowed to use realtime scheduling." and "Please check your /etc/security/limits.conf for the following line" Now this took me four hours so far without success and I wonder what is a functional way to use jackd via systemd on a headless computer in 2019. All comments are very welcome! Peter