gnome ssh agent

Ref

add key

Run ssh-add on the client machine, that will add the SSH key to the agent.

list added keys

Confirm with ssh-add -l (again on the client) that it was indeed added.

manual

Here are the steps to list the keys stored in your ssh-agent:

First, ensure that the ssh-agent is running and your keys are loaded into it. You can check this by running:

# fingerprints of all the keys currently loaded in the ssh-agent.
ssh-add -l

If the above command returns an error saying "Could not open a connection to your authentication agent", you'll need to start the ssh-agent and load your keys into it. You can do this by running:

eval $(ssh-agent)
ssh-add

The eval $(ssh-agent) command starts the ssh-agent and sets the necessary environment variables. The ssh-add command then loads your default SSH keys (usually ~/.ssh/id_rsa and ~/.ssh/id_ed25519) into the agent.

Once your keys are loaded, you can list them again using:

# fingerprints of all the keys currently managed by the ssh-agent
ssh-add -l

If you want to see the full public key contents instead of just the fingerprints, you can use:

# full OpenSSH public key format
ssh-add -L