Is there a way to run a Gui application (X11) in background so that if I disconnect, I can resume the running app again?I am using SmarTTY on windows to connect to remote CentOS. When I run a Gui application (e.g. gnome-help) it starts Xming server and displays its window. I want to keep it running even if I disconnect, crash or close ssh connection. So that I can get back to running applicaition later.I have tried 'screen' and '&' and combination of both but neither works. I can not connect again to the GUI application when SSH connection is closed.--EDIT--  As answered by AnthonInstall both the VNC Server and VNC Viewer on the remote system (e.g. CentOS).  Start VNC Server on remote Xvnc -localhost :13 Start VNC Viewer so that it displays locally via X (e.g. on your Windows)Set display export DISPLAY=:13Start a GUI application and it will be displayed in the VNC Viewer
Run a GUI application in background and reconnect later
ssh;x11;background process;xming
The X application needs a screen to connect to and normally (if you connect via ssh using -X that is your local screen). What you can do instead is use Xvnc and create a virtual screen for you X application to connect to and then, after logging back in, use a vncviewer to observe what is happening on this virtual screen. This functions in a similar way as using screen or tmux for terminal sessions.You start Xvnc via:  Xvnc -localhost -SecurityTypes=None :13with 13 being a unique number. You use this number to set your DISPLAY environment variable before starting the X application.During startup Xvnc will tell you which port to use to connect (5913 in my case). If you do not specify -localhost you can connect over the network directly using a vnc viewer without first having to login using ssh (this depends on your firewall of course, and you should use password protected connections instead of -SecurityTypes=None)On Debian based systems you can install Xvnc from the package vnc4server