Add Keypair to existing EC2 instance

Question

I was given AWS Console access to an account with 2 instances running that I cannot shut down (in production). I would however like to gain SSH access to these instances, is

Answer 1

You can just add a new key to the instance by the following command:

ssh-copy-id -i ~/.ssh/id_rsa.pub domain_alias

You can configure domain_alias in ~/.ssh config

host domain_alias
  User ubuntu
  Hostname domain.com
  IdentityFile ~/.ssh/ec2.pem