Generate Private/Public key pair for SSH connection on MacOS / Linux

 1. use keygen on Client PC to generate ed25519 key pair stored in ~/.ssh/, their default name are id_ed25519 and id_ed25519.pub, and the account names on Client PC and Server are the same.    # .pub is public key and non .pub is private key

$ ssh-keygen -t ed25519               #you should setup a passphrass

2. check and copy the public key to remote server

$ ssh-copy-id -n YourAccount@YourServer  # YourAccount stands for the account names on Client PC and Server, -n: try run

$ ssh-copy-id  YourServer

3. connect by ssh tunnel form client to Server as figure 1.

$ ssh YourAccount@YourServer      # authenticate with  passphrass only, not account password on Server

(Figure 1.)

4. Finally, if you want to passwordless login with ssh, empty passphrase while executing ssh-keygen processing

References

LPIC-1 STUDY GUILDE, SYBEX