Wireless Hacks

Hack 95 "Turbo-Mode" SSH Logins

Even faster logins from the command line.

If you've just come from the previous two hacks, you've only seen half of the solution! Even with client keys, you still have to needlessly type SSH server every time you want to SSH in. Back in the dark, insecure, unenlightened days of rsh, there was an obscure feature that I happened to love, which hasn't (yet) been ported to SSH. It used to be possible to symlink /usr/bin/rsh to a file of the same name as your server. rsh was smart enough to realize that if it wasn't called as rsh, that it should rsh to whatever name it was called as.

Of course, this is trivial to implement in shell. Create a file called SSH-to with these two lines in it:

 #!/bin/sh
 ssh `basename $0` $*

(Those are backticks around basename $0.) Now put that in your PATH (if ~/bin doesn't exist or isn't in your PATH already, it should be) and set up symlinks to all of your favorite servers to it:

 $ cd bin
 $ ln -s ssh-to server1
 $ ln -s ssh-to server2
 $ ln -s ssh-to server3

Now, to SSH to server1 (assuming you've copied your public key over as just described), simply type server1 and you'll magically end up with a shell on server1, without typing ssh, and without entering your password. That $* at the end allows you to run arbitrary commands in a single line (instead of spawning a shell), like this:

 server1 uptime

This will simply show the uptime, number of users, and load average on server1, then exit. Wrap it in a for loop and iterate over a list of servers to get a pinpoint status of all of your machines.

I believe that this is the quickest way to use SSH, short of setting up single character aliases to do it for you (which is excessively hackish, unmaintainable, and unnecessary, although it does seem to impress some people):

 $ alias a='ssh alice'
 $ alias b='ssh bob'
 $ alias e='ssh eve'
 ...

At any rate, SSH has many options that make it a very flexible tool for securely navigating between any number of servers. Now if we can just find a way to make it log in and actually fix the machine for you, we'd have a real hack.