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I got this problem...

My machine is a Windows(S1), who needs to connect to a Linux Server(S2) [used like a jumpbox], to connect with Linux Server(S3), which is the target machine.

I got Putty and Xming well configured, since I can open Firefox browser on S2; but when I connect to the S3 via SSH I can't open any X app there. I installed the xclock so I can test it, and I got this message:

Error: Can't open display

My proceedure is: Windows >putty> LinuxS2 >SSH> LinuxS3. Can open X apps on Linux S2, but not on Linux S3.

The networks between Windows and Linux S3 are differente, that's why the Linux S2 exists.

DMarracho
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  • You can do the equivalent of the *nix `ProxyCommand` in putty just where you multiple links chained together. In doing this you can make your client act as if you are directly connecting to the far host. http://mikelococo.com/2008/01/multihop-ssh/ https://superuser.com/a/949779/2057 – Zoredache Nov 16 '17 at 18:27
  • Do you connect with **-X** from s2 to s3? – Nils Nov 16 '17 at 20:05
  • Yes, I always connect like: ssh -X user@Ip I don't know what to do... on the first server I can open Firefox, but when I connect to the target, I can't open the xclock. Already checked everything, and even so I can't do it =/ Thank you anyway! – DMarracho Nov 17 '17 at 14:54

1 Answers1

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In your Putty session:

1) you need to enable Connection => SSH => X11 Forwarding

2) invoke ssh to S3 with -X option in Connection => SSH => Remote Command , for example : ssh -X user@S3

In S2 and S3, the /etc/ssh/sshd_config need to have X11Forwarding set to yes. (restart sshd when changing this).

The DISPLAY should be set to a value starting from value of X11DisplayOffset in sshd_config of S3.

And hopefully, this should make it work.

tonioc
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  • Thanks for your help! I got everything configured like you said... but I don't get the last step very well... What I need to do with DISPLAY? Thanks – DMarracho Nov 17 '17 at 08:33
  • Actually, you don't need to do anything with DISPLAY except checking it is given a value: "echo $DISPLAY" should show something like "10:0". If it is empty, this means some stuff is missing. Did you get it working? – tonioc Nov 18 '17 at 09:47
  • No, not yet... And i got everything configured like you said. When I enter echo $DISPLAY nothing happens on LinuxS3 =S – DMarracho Nov 21 '17 at 11:36
  • This means for some reason the X11Forwarding is not enabled. – tonioc Nov 22 '17 at 12:33
  • 1) check $DISPLAY on intermediate server S2 with a ssh (putty with X11 forwarding option but ithout the second ssh command in). Echo $DISPLAY should show something there. 2) on your server S3, check the sshd log (set LogLevel VERBOSE in /etc/ssh/sshd_config and look in syslog ) 3) maybe you could post your sshd_config: grep -v -E '^\s*#|^\s*$' /etc/ssh/sshd_config – tonioc Nov 22 '17 at 12:40