SSH

Generate a new SSH key

ssh-keygen

Upload public key

use scp to copy the public key to a remote machine.

scp C:/Users/USER/.ssh/id_rsa.pub ubuntu@192.168.2.3:~/id_rsa.pub

Specify port

scp -P 2222 C:/Users/USER/.ssh/id_rsa.pub ubuntu@192.168.2.3:~/id_rsa.pub

Log in to your Linux server using your username and password

ssh ubuntu@192.168.2.3

then

cat ~/id_rsa.pub >> ~/.ssh/authorized_keys

Set private key permission

Windows

Remove all except for the key's user.

Linux

chmod 600 ~/.ssh/id_rsa

Specify private key

ssh -i "C:\Users\USER\.ssh\id_rsa_other" root@192.168.2.3