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up vote 7 down vote favorite
2

I have to set up a tunnel between two hosts.

For this i use ssh in this way:

ssh -L MY_LOCAL_PORT:FOREIGN_ADDRESS:FOREIGN_PORT MYUSER@SSH_SERVER

after that, I login into my SSH_SERVER.

How can I avoid this feature?! I have only to set up a tunnel. I don't have to login into my SSH_SERVER...

I've tried the -N option, but it keep my shell busy

share|improve this question
    
SSH -N -L xx:xx:xx user@server & <-- have you tried that before ? –  Lawrence Nov 12 '13 at 7:45
    
Yes, but it doesn't work. When i try to connect with ssh via tunnel, the client tries to connect but it doesn't receive any reply. –  Bau Miao Nov 12 '13 at 8:03
    
Hey, you have right. I've tried on another host and the -N option works. So I've discovered that the problem is on my ssh client (I don't know why, and I will search the reason). Thanks a lot! –  Bau Miao Nov 12 '13 at 9:41

3 Answers 3

up vote 7 down vote accepted

As said in other posts, if you don't want a prompt on the remote host, you must use the -N option of SSH. But this just keeps SSH running without having a prompt, and the shell busy.

You just need to put the SSH'ing as a background task with the & sign :

ssh -N -L 8080:ww.xx.yy.zz:80 user@server &

This will launch the ssh tunnelling in the background. But some messages may appear, especially when you try to connect to a non-listening port (if you server apache is not launched). To avoid these messages to spawn in your shell while doing other stuff, you may redirect STDOUT/STDERR to the big void : 

ssh -N -L 8080:ww.xx.yy.zz:80 user@server >/dev/null 2>&1 &

Have fun with SSH.

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Thanks, your solution is the most graceful! –  Bau Miao Nov 12 '13 at 9:44
2  
You can also use ssh option -f instead of & and io redirection. –  tkrennwa Nov 13 '13 at 13:49
up vote 0 down vote

You need to log in to the remote host to set up your tunnel.

However you do not need to run a shell there. man ssh says:

 -N      Do not execute a remote command.  This is useful for just for‐
         warding ports (protocol version 2 only).
share|improve this answer
up vote 0 down vote

-f -N is what you are looking for:

ssh -f -N -L MY_LOCAL_PORT:FOREIGN_ADDRESS:FOREIGN_PORT MYUSER@SSH_SERVER
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