Home / ubuntu / Questions / 1160386
Accepted
nobody
Asked: 2019-07-24 02:49:58 +0800 CST

pacat -p some file in backup-skript needs $DISPLAY for X11 why?

  • 772

I wrote an udev-rule and a systemd-unit, so if I plugin a particular harddrive rsync backups my /home in background and play a audio file when ready.

During my first attempt I get following error pulseaudio[8802]: [pulseaudio] main.c: Unable to contact D-Bus: org.freedesktop.DBus.Error.NotSupported: Unable to autolaunch a dbus-daemon without a $DISPLAY for X11

Note this I have fixed. I got my sound back after skript is ready.

But I don't understand why pacat or even aplay needs this variable for playing only audio. I'm runnning ubuntu bionic with xfce4-session.

sound pulseaudio backup rsync 18.04

1 Answers

  1. Best Answer

    Both aplay and pacat are userland programs, so the easiest way for the programmer to get the sound out there is to use the dbus library as no one in their right mind is going to use these in cron, or in a udev rule, or heaven forbid in systemd, right??? :-)

    Well, they were right until you came along, and you indeed took the correct solution to solve this issue.

    If you would like to be able to make a sound without X running at all (E.G. a headless server), you might echo the ASCII BEL¹ character to a tty.

    Note 1: 007: really retro: a beep was more important then a Line Feed (10), Form Feed (12) or Carriage Return (13)...

    • 1