For Unix, what are ssh-agent and ssh-add, and how do I use them?

Source taken from http://kb.iu.edu/data/aeww.html

In Unix, ssh-agent is a background program that handles passwords for SSH private keys. The ssh-add command prompts the user for a private key password and adds it to the list maintained by ssh-agent. Once you add a password to ssh-agent, you will not be prompted for it when using SSH or scp to connect to hosts with your public key.

To use ssh-agent and ssh-add, follow the steps below:

1. At the Unix prompt, enter: eval `ssh-agent` Note: Make sure you use the backquote ( ` ), located under the tilde ( ~ ), rather than the single quote ( ' ).
   
   
2. Enter the command: ssh-add
3. Enter your private key password.
   
   
4. When you log out, enter the command: kill $SSH_AGENT_PID To run this command automatically when you log out, place it in your .logout file (if you are using csh or tcsh) or your .bash_logout file (if you are using bash).

Note: The versions of these programs for SSH2, ssh-agent2 and ssh-add2, are the same as outlined above. To use them, follow the instructions above, replacing all occurrences of ssh-agent with ssh-agent2 , and ssh-add with ssh-add2 . The SSH2 versions will only work if both your computer and the remote host are running SSH2.