I have upgraded my main server from Cent OS 8 Stream to Rocky 9.5 and most stuff is working but not x11 forwarding so I can’t open GUI tools like gedit and meld etc.
I haven’t changed anything on my Mint client which was working before the server upgrade. On the server the non comment lines of /etc/ssh/sshd.config are:
When connecting and trying to start gedit there are no error messages and ps suggests it is running but nothing appears on my client screen. Here is the terminal output with the verbose option:
david@shigoto:~$ ssh -v -Y root@ichi
OpenSSH_8.9p1 Ubuntu-3ubuntu0.10, OpenSSL 3.0.2 15 Mar 2022
debug1: Reading configuration data /home/david/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to ichi [10.20.1.1] port 22.
debug1: Connection established.
...
debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.10
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.7
debug1: compat_banner: match: OpenSSH_8.7 pat OpenSSH* compat 0x04000000
debug1: Authenticating to ichi:22 as 'root'
...
Authenticated to ichi ([10.20.1.1]:22) using "publickey".
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: exec
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: client_input_hostkeys: searching /home/david/.ssh/known_hosts for ichi / (none)
debug1: client_input_hostkeys: searching /home/david/.ssh/known_hosts2 for ichi / (none)
debug1: client_input_hostkeys: hostkeys file /home/david/.ssh/known_hosts2 does not exist
debug1: client_input_hostkeys: host key found matching a different name/address, skipping UserKnownHostsFile update
debug1: Remote: /root/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /root/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Sending environment.
debug1: channel 0: setting env LANG = "en_NZ.UTF-8"
debug1: channel 0: setting env LC_MESSAGES = "en_NZ.UTF-8"
debug1: channel 0: setting env LC_CTYPE = "en_NZ.UTF-8"
debug1: channel 0: setting env LC_COLLATE = "en_NZ.UTF-8"
Web console: https://ichi:9090/
Last login: Fri Feb 14 10:44:08 2025 from 10.20.2.1
[root@ichi ~]# gedit
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from ::1 36336
debug1: channel 1: new [x11]
debug1: confirm x11
debug1: channel 1: FORCE input drain
debug1: channel 1: free: x11, nchannels 2
In other words, SSH does not say that X11 forwarding is not possible and it also tells (via DISPLAY) to X11 clients which X11 server to talk to.
Now the question is, what do the X11 clients say when they try to start (and fail)?
Is it possible on the Mint’s X11 server to log what happens when client tries to start?
The extra debug info in my last post was from the Mint ssh client. I thought I would try and get extra info from gedit itself. Checking it’s command line options there is no verbose option but I did notice the option --display=DISPLAY X display to use so I tried gedit --display=localhost:15.0 and that worked!
Trying meld didn’t wok and if does not have a display option. On the other hand gitk worked straight away.
I guess this means with Cent OS 8 programs didn’t need to know much about X11 sessions or the defaults worked ok where as with Rocky 9 the defaults don’t suit all programs.
More progress. It look like the problem is Wayland and the gui programs are probably opening on the server’s local screen. I can get meld to work using GDK_BACKEND=x11 meld.
So I can seem to run all the main GUI programs I use, even if the solution is a bit clumsily. There is probably a better way to deal with this. It sounds like if I can stop Wayland running that may solve the problem.