About ssh-agent and ssh-add in Unix

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.

The public part of the key loaded into the agent must be put on the target system in ~/.ssh/authorized_keys; see Set up SSH public key authentication to connect to a remote system.

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

1. At the Unix prompt, enter:

    eval `ssh-agent`

   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).