PFMacLog

Leopard comes with a built-in SSH agent. The passphrase of your private key can be stored in your keychain.

SSH Dialog

If you don’t want to store your passphrase in the keychain, the above dialog will appear every time you use the ssh tool with your private key. It’s so boring, isn’t it? Ok, ssh-add can solve it.

ssh-add <private key file>

It adds your private key to the SSH agent. After using this command, you won’t see that dialog again in the current system login session.