An SSH key has two pieces, the public key and the private key.
The private key:
id_rsa
, but it can be given any name.chmod 600 id_rsa
Its parent directories should also not be world-writable.The public key:
id_rsa.pub
, but it can be given any name.ssh-keygen -y -f ~/.ssh/id_rsa
$HOME/.ssh/authorized_keys
on the remote system to enable passwordless login with the private key. (AWS does this for you at instance creation for the keypair you select. They cannot update this file for you after instance creation.)