things I didn’t know until today
okay, so I guess I kinda knew them but had never tried them.
1. generate rsa key using openssl or what not
2. have the private key on disk in a .pem file
3. run ssh-keygen -y -f myprivatekey.pem > ~/.ssh/authorized_keys
4. ssh -i myprivatekey.pem user@host_with_pub_key_on_it
simple as pie.