SSH Tunneling of X protocol from noninteractive session Distribution: world

But all -X or -Y do, when going from M to C, is open a tunnel from (typically) C:6010 to (typically) M:6000. Plus handle xauth protocol; without that, you'd need to do xauth processing "by hand".

So, since you will be running an ssh session to keep the tunnel open, why not just run an ssh session and keep the same tunnel open with -X?

Possibly, because you don't want to have a shell left running on C? You could use some other innocuous process rather than a shell; that might not work with -N, though.

In any event, if you are launching the debug by a non-interactive process, and then rendezvousing with it later, I'd suggest using Xvnc, (or Xvfb with x11vnc or the like), so that the debugging session could launch its own X server, rather than just a proxy. This has the advantage that if the network goes down, you can reconnect to your debugging session.

So. On C, to start the debugger, something like

Xvnc :1 & env DISPLAY=:1 xterm -e gdb myexecutable &

(though possibly you may also want to run a window manager), and then on M, you use vncviewer with -via, or an explicit ssh tunnel and vncviewer to localhost, to rendezvous with the debugger. You may also want to use some other Xvnc options, such as -auth and -rfbauth for authentication and pbuttwords, and -localhost to encourage use of tunneling and encryption. Or possibly use the vncserver script to launch the Xvnc.

Pros: you can reconnect, you can collaborate, you don't need to launch the debugger while you have the tunnel running, your X services are done locally with much lower latency.

Cons: the server must have Xvnc installed, what's transported to the remote site is a bitmap, you are consuming more resources on C.

Note, of course, that if you are using gdb, you could launch it under "screen" also, and wouldn't need X at all; depends on what else you'd be using X for, but if you run an xterm on M, then an ssh session to reach M, then screen -r to attach to the existing gdb session, you'd have the same capabilities as if you were running the xterm on M displaying to C, but less data would be going between M and C.