How to detect when Xorg freezes?

Published: April 05, 2023Updated: May 03, 2023

Table of contents

Investigation begins
Restart Xorg and save the app
- xmove
- xpra
References

Sometimes Xorg just freezes. Maybe it's caused by my graphical app, or maybe not. Here's what I see in .xsession-errors.old

The server closed the connection.
The server closed the connection: socket, pipe or stream error.

And also another type of errors

Failed request: ChangeProperty, BadWindow: 0x00800003.

Investigation begins

Let's find out how Xorg is started and with what arguments. On a system with lightdm you run systemctl status lightdm and find this

/usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch

Another place is nano /etc/X11/xinit/xserverrc.

The -nolisten flag means that no TCP connections on port 6000, but only unix socket. To enable TCP you need to create a file nano /usr/share/lightdm/lightdm.conf.d/50-nick-test.conf with this content

[Seat:*]
xserver-allow-tcp=true

(Source: nolisten flag added to the command line set by setting from config here)

Then after reboot you will see the Xorg listening on port 6000 with netstat -lpnt (install it with apt install net-tools)

tcp        0      0 0.0.0.0:6000            0.0.0.0:*               LISTEN      894/Xorg

Also open ssh X11 forwarding for our experiments nano /etc/ssh/sshd_config:

X11Forwarding yes

I looked into implementation of the XOpenDisplay function. So, basically I need to test the open a connection with XCB (docs)

Restart Xorg and save the app

I didn't find any tools to make this proposition to work. But here's a list of tools I looked at

The answer Possible to move a window from one X screen to another on same host?
another small answer Recover an application in sleeping state after an X server crash
X2Go
Guievict - A system for checkpointing and migrating the GUI of an X window application (github)

xmove

xmove - github

xpra

xpra (github , site, ArchWiki) Can xpra use opengl framebuffer?

wget -O /usr/share/keyrings/xpra.asc https://xpra.org/gpg.asc
wget -O /etc/apt/sources.list.d/xpra.sources https://raw.githubusercontent.com/Xpra-org/xpra/master/packaging/repos/bionic/xpra.sources