Update existing SSH private key

If your private key is still in an old or unsecure format (e.g. without a passphrase), you can update it using the following command.

ssh-keygen -p -f ~/.ssh/id_rsa

It will prompt for your old (if any exists) and your new passphrase. It will also prompt for the keyfile path (with suggestion) if you do not provide the -f key-file option at all. (~/.ssh/id_rsa is just an example. Could be id_dsa or any other filename as well.)

After adding a passphrase for your existing key, you can use ssh-add so that you only need to enter your password once for a session.

ssh-add ~/.ssh/id_rsa