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I'm trying to run a python GUI application as a service. The application is using PyQt5 and python-vlc packages. I have the following service file:

[Unit]
Description="Python VLC Service Test"
After=multi-user.target

[Service]
Type=simple
User=pi
Environment="DISPLAY=:0"
Environment="XAUTHORITY=/home/pi/.Xauthority"
ExecStart=/usr/bin/python3 /opt/experimental/vlc_pyqt.py
Restart=on-failure

[Install]
WantedBy=graphical.target

However, when playing video in the vlc window, only white screen shows up. After looking in journalctl I found these two errors:

Aug 18 16:26:27 raspberrypi python3[17754]: [83ab02c8] dbus_screensaver inhibit error: cannot connect to session bus: Failed to connect to socket /tmp/dbus-ZeiFpFnTZO: Connection refused

Aug 18 16:26:33 raspberrypi python3[17754]: [84f28b10] mmal_codec filter error: Failed to alloc CMA buf: fmt=Z420, size=3133440

I think the CMA buffer error is a result of the first one. Any ideas how to fix it? The application is running just fine when run directly (not as a service).

I would like to run it as a service in order to be able to monitor the status of the application via systemctl status vlc_pyqt.service as the application should run all the time on the machine and to be able to gracefully restart it by systemctl restart vlc_pyqt.service if needed.

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    Possibly because the X display on :0 doesn't belong to pi before anyone logs in (running a service as a specific user does not involve a login) -- although why it opens the app at all then I dunno.
    – goldilocks ♦
    Aug 18, 2021 at 15:37
  • Thanks for your comment, I am already logged in as the pi user when testing this. I tried to run sudo systemctl --user start vlc_test.service but got Aug 23 18:52:51 raspberrypi systemd[574]: vlc_test.service: Failed with result 'exit-code'. Any ideas how to fix this? I could not find anything explaining what could have gone wrong
    – Kwigon
    Aug 23, 2021 at 16:54
  • Do you have any logging in vlc_pyqt.py? If not, do not pass go, do not collect $200, etc. systemclt status ... may give a bit more information. There's kind of a pseudo/semi XY problem here, in that it's hard to see why you want to run this as a service. If it's because you want it to run at boot, this is probably a bad method; you should use autostart via the DE. If you are trying to get it to run at boot, then it seems completely pointless.
    – goldilocks ♦
    Aug 24, 2021 at 15:43
  • I would like to run it as a service to be able to monitor the status of the application via systemctl status vlc_pyqt.service as the application should run all the time on the machine and be able to gracefully restart it by systemctl restart vlc_pyqt.service if needed. I will add it the explanation the question. Regarding logging: systemctl status showed only the last few messages and no more than journalctl I mentioned in the question. Those two errors do not happen when I run it the standard way. I will post a complete log from the vlc in a few hours.
    – Kwigon
    Aug 25, 2021 at 14:25
  • "I would like to run it as a service to be able to monitor the status of the application via systemctl status vlc_pyqt.service" -> This is a bad reason. Whatever you are trying to accomplish with that should be done by incorporating proper logging and controls in the application.
    – goldilocks ♦
    Aug 26, 2021 at 14:09

1 Answer 1

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I encountered a similar issue when trying to run VLC from a systemd unit with mmal-codec output.

Thanks to this answer I was able to make it work :

https://forum.videolan.org/viewtopic.php?t=154020#p505537

If that's an option for you, you can put the systemd unit file in '~/.config/systemd/user/', making sure to remove the User= and Environment= directives, so with your example :

[Unit]
Description="Python VLC Service Test"
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/python3 /opt/experimental/vlc_pyqt.py
Restart=on-failure

[Install]
WantedBy=graphical.target

then after that, reload the daemon, enable/start the service with

systemctl --user daemon-reload
systemctl --user enable yourservicefilename.service
systemctl --user  start yourservicefilename.service

Hope it resolves the problem for you, or can help someone out there !

EDIT: Here is my unit file for running VLC as a service with http interface :

[Unit]
Description=VLC http service

[Service]
WorkingDirectory=/home/pi/
ExecStart=/usr/bin/cvlc -I http --no-osd --http-password=foo --http-host=127.0.0.1 --http-port=8000
Restart=always

[Install]
WantedBy=default.target

Notice that in the WantedBy= directive, I used 'default.target' as I'm on a cli environment ( no gui/desktop ). Also notice the absence of After= directive in the '[Unit]' section. If you find that your service does not auto-start at boot, you should check these as it's probably due to one of those conditions not being met.

Source : https://bbs.archlinux.org/viewtopic.php?id=250813

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