Keychain

Keychain can be used to add SSH keys to the ssh-agent. Keychain does not come pre-installed on most systems, so first install Keychain:

sudo apt install keychain

Add an SSH key to Keychain

To add a private SSH key to Keychain, execute:

keychain ~/.ssh/id_ed25519

This process can be automated by having this command in the Bash or Zsh configuration file.

Keychain has the benefit of starting ssh-agent if it has not already been started, and can be used to add GPG keys.

List loaded SSH keys

Use the -l flag to list all the loaded SSH keys:

keychain -l