How to solve “Could not open a connection to your authentication agent”


You want to add a ssh key using ssh-add. It fails with this message:

Could not open a connection to your authentication agent.


ssh-agent manages the keys added by ssh-add. Even if there is already an instance running, the current shell instance may not be aware of it –  ssh-agent sets the environment variable SSH_AGENT_PID.

In order to start a new instance of ssh-agent, execute this command:

eval $(ssh-agent)

If yo use this approach on a server (which isn’t rebootet regularly), an enormous amount of running ssh agents is accumulated over time. Therefore you might want to execute killall ssh-agent from time to time to kill all ssh-agent instances you can’t use any more (because you can’t access the environment variables any more).