<NME> xdummy.conf
<BEF> [program:xdummy]
command=bash -l -c "xinit -- :0 -nolisten tcp vt$XDG_VTNR -noreset +extension GLX +extension RANDR +extension RENDER +extension XFIXES"
environment=USER=root,QT_X11_NO_MITSHM=1
directory=/root
autorestart=true
stdout_logfile=/var/log/supervisor/xdummy.log
redirect_stderr=true
redirect_stderr=true

<MSG> Run the X session as a normal user.

This addresses the following error in the log file:

  stdin: is not a tty

<DFF> @@ -1,7 +1,7 @@
 [program:xdummy]
 command=bash -l -c "xinit -- :0 -nolisten tcp vt$XDG_VTNR -noreset +extension GLX +extension RANDR +extension RENDER +extension XFIXES"
-environment=USER=root,QT_X11_NO_MITSHM=1
-directory=/root
+environment=HOME=/home/user,USER=user,QT_X11_NO_MITSHM=1
+directory=/home/user
 autorestart=true
 stdout_logfile=/var/log/supervisor/xdummy.log
 redirect_stderr=true

Run the X session as a normal user.