Beginners • Re: starting systemd service after GUI is up

Have a dashboard application running here
- based on bookworm
- RPi2, official LCD
- python tkinter, fullscreen. Data received by MQTT.
- started by systemd, After=graphical.target, WantedBy=graphical.target; Environment="DISPLAY=:0"
works good

Just upgraded to trixie 32Bit (RPi2) and found that at system start
- python program, tkinter complains " _tkinter.TclError: couldn't connect to display ":0""
Program continues to run (some tkinter thing), but does not work.

- systemctl start ..service works from the command line some time after boot
- had to catch this exception and force an exit of the program os._exit(1)
- added Restart=always to force retries by systemd
Fails on first startup, third attempt by systemd succeeded; 33 seconds after first attempt.

Looks as if DISPLAY=:0 is not ready immediately after reaching the target graphical.target.
There's some fairy dust missing, obviously.

Statistics: Posted by ghp — Fri Jan 16, 2026 8:36 pm

---