X-Windows

GUI windowing system as used on most Posix systems. Aka X11, Xorg

Tips

Over SSH

ssh -X user@host

should automatically forward X11 connections from remote host to local X server (display).

Direct connections

Enable on, eg. Debian Buster, by modifying /etc/X11/xinit/xserverrc to change "-nolisten tcp" to "-listen tcp", then restart display manager (eg. lightdm).

After getting a local X session running, get XAuth token:

xauth list $DISPLAY

Make sure client machine has xauth installed (apt install xauth).

Set DISPLAY environment variable:

export DISPLAY=server.machine:0

Set XAuth token (from above):

xauth add $DISPLAY MIT-MAGIC-COOKIE-1 ...

start X client apps (eg. xclock, xeyes, xterm etc.).

External links

• https://www.linuxquestions.org/questions/linux-newbie-8/xlib-connection-to-0-0-refused-by-server-xlib-no-protocol-specified-152556/#post791278
• https://unix.stackexchange.com/questions/85782/error-no-protocol-specified-when-running-from-remote-machine-via-ssh
• https://mirror.linux.org.au/pub/linux.conf.au/2020/room_8/Thursday/A_Political_History_of_X.webm