Route 19

I frequently log in to various servers via SSH, and like to share an SSH key so I don’t need to type the password every time. Here’s a quick step by step for doing so from Mac OS 10.5 to an Ubuntu 9 server (so I don’t have to look for instructions anymore).

The idea is to create a key pair, one public and one private. The private key stays on your local system and the public key goes to the remote server(s). First, if you don’t already have a public/private key pair, create one on your Mac:

ssh-keygen

Follow the instructions to create an RSA pair, ~/.ssh/ is the default location. Copy the public key to your server (replace domain.tld with your server name, and /home/username with your home directory):

scp ~/.ssh/id_rsa.pub domain.tld:/home/username

Now you can SSH into your server…

ssh domain.tld

And check for an existing .ssh directory:

ls -al ~/

If it doesn’t exist, create it and make it private:

mkdir ~/.ssh chmod 700 ~/.ssh

Move your public key to the ~/.ssh directory:

mv ~/id_rsa.pub ~/.ssh

Check if there’s an existing authorized_keys file:

ls -al ~/.ssh

If there isn’t you can simply rename your key and make it private:

mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys chmod 600 ~/.ssh/authorized_keys

If you already had an ~/.ssh/authorized_keys file you can append your new key like so:

cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

Now you should be able to exit the server and the next time you log in you won’t be prompted for a password. You can add your public key to the authorized_keys file of several servers.