enable ssh key login

1. generate private/public key

generate private key.

$ ssh-keygen -t rsa -b 4096

generate public key from private key

$ ssh-keygen -y -f ./<privateKey>.pem

2. add public key to authorized_keys

$ echo <publicKey> >> /root/.ssh/authorized_keys

3. enable public key login

# edit sshd config
# PubKeyAuthentication yes

$ vi /etc/ssh/sshd_config
$ systemctl restart sshd

4. login with ssh key

$ ssh -i <privateKey> user@host