SSH Notes

Auto Login

To auto-login to other machines you must generate a key:

ssh-keygen

# Don't enter anything at the prompts. If you enter a pass-phrase
# then you will need to enter that every time you use this key.
# which defeats the purpose of doing this.

...and copy the key to the server you wish to login to:

cat ~/.ssh/id_rsa.pub |ssh you@server "cat >> .ssh/authorized_keys2"

After that you can login to that box with no password.

Tunneling

Forward ports from one machine to another. Handy for boxes behind firewalls.

ssh -g -L 3306:localhost:3306 you@server

# Forward the mysql port through the ssh port from localhost to
# your server. (Much more secure too!)

Login as if you were logging in to localhost. Also handy:

ssh -R 5901:localhost:5901 you@yourhost.com
# Reverse Tunnel
# Now run vnc on yourhost.com as if on localhost

STDIN STDOUT

STDIN and STDOUT can be redirected between machines through ssh.

# Copy a file between boxes:
cat file.ext |ssh otherbox "cat > file.ext"

# tar and gz some stuff and transfer it to another box:
tar -cf - dir_to_backup |gzip -c -9 |ssh otherbox "cat > the_backup.tar.gz"

# ...or decompress it when it gets to the other box. Handy for transfering
# large (or a lot of) files to save bandwidth:
tar -cf - lots of big files |gzip -c -9 |ssh otherbox "tar zxvf - -C /path/for/to/decompress"