Using SSH for tunneling, kicking users, etc

A very useful resource (in French) to use SSH, with specific use cases: http://pix-mania.dyndns.org/mediawiki/index.php/OpenSSH#Les_tunnels_SSH

Another useful (and short one for tunneling): http://www.howtoforge.com/reverse-ssh-tunneling

In short, if you have a configuration with 3 computers (A – B – C) and you want to connect to A from C but A doesn’t allow direct SSH connection, you can do the following:

1. On A and B, install openssh-server
2. On A, open an SSH connection to B: ssh -R 5000:localhost:22 user-on-B@B
3. From C, connect to B: ssh user-on-B@B
4. Using the open connection on B, open a connection to A: ssh -p 5000 user_on_A@localhost

This should get you all ready to work on A.

Another special case is you have A-B-C, you are on C and want to access the internal website running on A, but you can only access B in SSH, and from B, access A.

1. Install openssh-server on A and B
2. From C, instruct your SSH client to connect to B and to link your local port 8080 to A’s port 80: ssh -L 8080:A.A.A.A:80 user_on_B@B.B.B.B
3. Open your browser on http://localhost:8080