Normally, we'd expect ssh X forwarding to work as simply as specifying -X. However, sometime after I updated from Redhat 8 to 9 or after I installed the openssh 3.7.1p rpm's, X forwarding does not work.

Specifically, the DISPLAY environment is not automatically set. I remember it used to be set to :10.0 in the good old days. Now, the variable is not initialized. Any advice is appreciated.

btw, I feel bad for sysadmins administrating older systems. Openssh 3.7.1 requires a newer openssl which causes dependencies to be broken. Even wget doesn't won't work. Hopefully no one is getting screwed yet. The last thing Linux needs is bad press. (did i digress?)

mars:/home/micxz # cat /etc/ssh/ssh_config | grep X
# ForwardX11 no

Maybe you need to change this?

I'm having the same issue after upgrading to openssh 3.7.1p as well. I do have X11 Forwarding enabled in /etc/ssh/sshd_config so thats not the problem. I think it is the DISPLAY variable but I forget how and what I need to change it to.