Password free SSH in 3 steps

Sometimes you need to run a script, that needs to authenticate on another box. Adding your SSH Key to the other box is both quick, and easy.

Run the sshkeygen command to generate a key, if you havent already:

justin@local-host$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/justin/.ssh/id_rsa):[Enter key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Pess enter key]
Your identification has been saved in /home/justin/.ssh/id_rsa.
Your public key has been saved in /home/justin/.ssh/id_rsa.pub.
The key fingerprint is:
33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9 justin@local-host

Next we need to copy our key to the other instance.

justin@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
justin@remote-host's password:
Now try logging into the machine, with "ssh 'remote-host'", and check in:
.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.

If the above command doesnt work for you, just log in through a secure channel, and add the sshkey to /home/$user/.ssh/authorized_keys on it's own line.

Once the key is in place, you should be able to connect, if you generated a key with a password, enter it at the command prompt. Hitting should log you in.

justin@local-host$ ssh remote-host
Last login: Sun Nov 16 17:22:33 2008 from 192.168.1.2
justin@remote-host$ 

[Note: SSH did not ask for password.]

It's simplicity like this that makes me love working with Linux.