Missing "wait" system call
I'm using 0.65.0 and external commands leave zombies as shown below, I guess you forgot to call wait when a child die.
6958 ? Ssl 61:32 /usr/local/Repetier-Server/bin/RepetierServer -c /usr/local/Repetier-Server/etc/RepetierServer.xml --da
6977 ? Z 0:00 \_ [webcam]
7745 ? Z 0:00 \_ [omxplayer]
7763 ? Z 0:00 \_ [webcam]
10374 ? Z 0:00 \_ [webcam]
10533 ? Z 0:00 \_ [omxplayer]
10551 ? Z 0:00 \_ [webcam]
11095 ? Z 0:00 \_ [webcam]
6958 ? Ssl 61:32 /usr/local/Repetier-Server/bin/RepetierServer -c /usr/local/Repetier-Server/etc/RepetierServer.xml --da
6977 ? Z 0:00 \_ [webcam]
7745 ? Z 0:00 \_ [omxplayer]
7763 ? Z 0:00 \_ [webcam]
10374 ? Z 0:00 \_ [webcam]
10533 ? Z 0:00 \_ [omxplayer]
10551 ? Z 0:00 \_ [webcam]
11095 ? Z 0:00 \_ [webcam]
Comments
You can use "ps fax" command to show process tree on every linux distribution.
You'll have to add such line to /var/lib/Repetier-Server/database/extcommands.xml
<execute name="play" allowParams="false">/usr/bin/omxplayer /home/pi/sound/sound.mp3</execute>
Then run it on the startup event gcode and you'll show the omxplayer zombie after the next print.
The "webcam" command is a script I wrote to launch mjpg-streamer at print startup and kill it when done.
For example : http://www.microhowto.info/howto/reap_zombie_processes_using_a_sigchld_handler.html
In extcommands you can also define menu entries that execute commands directly from menu. Also from the global settings->terminal you could execute commands. Other cases are more internal.