SSH & Keys, Explained

What SSH actually is (an encrypted remote terminal into another machine), how key pairs replace passwords, and how to live with SSH day to day - config shortcuts, the agent, and the errors that bite everyone.

1. What SSH Is SSH is an encrypted terminal into another machine: ssh user@host opens a session, the first-connection fingerprint prompt is SSH asking 'is this really the server?', and a session is just a remote shell that ends when you log out.
2. Key Pairs, Demystified A key pair is a padlock (public key) you hang on the server and the only key (private key) that opens it; it beats passwords because no secret ever travels and it resists brute force. Generate one with ssh-keygen, keep it in ~/.ssh, and install the public half with ssh-copy-id.
3. Living With SSH Make SSH pleasant: ~/.ssh/config turns long host strings into short names, the ssh-agent remembers your passphrase for the session, and a cheat-card maps the common errors - Permission denied (publickey) and the changed host-key warning - to calm fixes.