Add SSH Key to ssh-agent on Ubuntu Linux

This article provides a quick, step-by-step guide on how to add a private SSH key to the ssh-agent on an Ubuntu Linux client. By caching your private key in the agent, you can establish secure SSH connections to remote servers without having to re-enter your key’s passphrase every time.

Step 1: Start the ssh-agent

Before adding your private key, you must ensure that the ssh-agent is running in the background. Open your terminal and run the following command to start the agent:

eval "$(ssh-agent -s)"

This command starts the agent and sets the necessary environment variables in your current shell session.

Step 2: Add Your Private SSH Key

Once the agent is running, use the ssh-add command followed by the path to your private key file to add it to the agent.

If you are using the default ED25519 key, run:

ssh-add ~/.ssh/id_ed25519

If you are using a standard RSA key, run:

ssh-add ~/.ssh/id_rsa

If your private key is stored in a custom location, replace the path accordingly:

ssh-add /path/to/your/private_key

If your key is protected by a passphrase, you will be prompted to enter it once. The ssh-agent will then store the decrypted key in memory.

Step 3: Verify the Added Key

To confirm that your private key has been successfully added to the ssh-agent, list the currently loaded keys with the following command:

ssh-add -l

This will display the fingerprint and the file path of all keys currently managed by the active agent.