To add a keypair to an existing Amazon EC2 instance, start by identifying the original instance. Next, identify the volume containing the broken root. Locate the second EC2 instance that you will use to fix the broken root. Start a temporary instance if you don’t already have an instance running. Stop the broken instance and detach it. Attach the new keypair. Terminate the temporary instance. Now you can “ssh” to allow multiple users to a single EC2 instance.