This is a debugging question. When you ask for clarification please make sure it is not already covered below.
I have 4 machines: Z, A, N, and M.
To get to A you have to log into Z first.
To get to M you have to log into N first.
The following works:
ssh -X Z xclock ssh -X Z ssh -X Z xclock ssh -X Z ssh -X A xclock ssh -X N xclock ssh -X N ssh -X N xclock
But this does not:
ssh -X N ssh -X M xclock Error: Can't open display:
The $DISPLAY is clearly not set when logging in to M. The question is why?
Z and A share same NFS-homedir. N and M share the same NFS-homedir. N's sshd runs on a non standard port.
$ grep X11 <(ssh Z cat /etc/ssh/ssh_config) ForwardX11 yes # ForwardX11Trusted yes $ grep X11 <(ssh N cat /etc/ssh/ssh_config) ForwardX11 yes # ForwardX11Trusted yes
/etc/ssh/sshd_config is the same for all 4 machines (apart from Port and login permissions for certain groups).
If I forward M's ssh port to my local machine it still does not work:
terminal1$ ssh -L 8888:M:22 N terminal2$ ssh -X -p 8888 localhost xclock Error: Can't open display:
A:.Xauthority contains A, but M:.Xauthority does not contain M.
xauth is installed in
/usr/bin/xauth on both A and M.
xauth is being run when logging in to A but not when logging in to M.
ssh -vvv does not complain about X11 or xauth when logging in to A and M. Both say:
debug2: x11_get_proto: /usr/bin/xauth list :0 2>/dev/null debug1: Requesting X11 forwarding with authentication spoofing. debug2: channel 0: request x11-req confirm 0 debug2: client_session2_setup: id 0 debug2: channel 0: request pty-req confirm 1 debug1: Sending environment.
I have a feeling the problem may be related to M missing in M:.Xauthority (caused by
xauth not being run) or that $DISPLAY is somehow being disabled by a login script, but I cannot figure out what is wrong.
-- update 20110628
I did not know about
sshrc so that was a good guess. But alas, not the problem here. It does not exist on any of the 4 machines:
$ ls ~/.ssh/rc /etc/ssh/sshrc ls: cannot access /home/tange/.ssh/rc: No such file or directory ls: cannot access /etc/ssh/sshrc: No such file or directory
As mentioned the $DISPLAY variable is not set on M, but is fine on A:
$ ssh -X N ssh -X M 'echo \$DISPLAY' <<empty>> $ ssh -X Z ssh -X A 'echo \$DISPLAY' localhost:14.0
The difference in output from a working session and a non-working session (Note: There are no warnings about X forwarding or xauth in the non-working session):
$ stdout ssh -X Z ssh -vX A 'echo \$DISPLAY' >/tmp/a $ stdout ssh -X N ssh -vX M 'echo \$DISPLAY' >/tmp/b $ diff /tmp/a /tmp/b 4c4 < debug1: Connecting to A [126.96.36.199] port 22. --- > debug1: Connecting to M [188.8.131.52] port 22. 23,24c23,24 < debug1: Host 'A' is known and matches the RSA host key. < debug1: Found key in /home/tange/.ssh/known_hosts:35 --- > debug1: Host 'M' is known and matches the RSA host key. > debug1: Found key in /home/tange/.ssh/known_hosts:1 43d42 < debug1: Sending env LC_ALL = en_US.UTF-8 46c45 < localhost:14.0 --- > 53,54c52,53 < Transferred: sent 2384, received 2312 bytes, in 0.2 seconds < Bytes per second: sent 10714.8, received 10391.2 --- > Transferred: sent 2336, received 2296 bytes, in 0.0 seconds > Bytes per second: sent 54629.1, received 53693.7
lsh-server instead of
openssh-server on M fixes the X-forwarding, but is an unacceptable solution.