ssh

Make a key pair with ssh-keygen, install it with ssh-copy-id, then log in to the server with ssh — no password.

>_ Try it: a simulated Linux, right herenothing runs on your computer

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Examples

ssh-keygen -t ed25519 make a key pair (private + .pub)
ssh-copy-id deploy@web-01 put the public key on the server
ssh deploy@web-01 hostname run one command there
ssh deploy@web-01 log in: the prompt changes
whoami you are deploy now
exit back to your own machine

How it works

ssh USER@HOST opens a shell on another machine: every command you type runs there, until exit brings you back.

Keys beat passwords: ssh-keygen makes a pair, a private key that never leaves your computer and a public key (.pub). ssh-copy-id puts the public one in the server's ~/.ssh/authorized_keys, and from then on the key logs you in.

Syntax

ssh [-i KEY] [-p PORT] USER@HOST [COMMAND]

Options

Option	What it does
`USER@HOST`	who to log in as, and where
`COMMAND`	run one command there and come straight back
`-i FILE`	use this private key
`-p PORT`	another port than 22
`ssh-keygen`	make a key pair (-t ed25519)
`ssh-copy-id`	install your public key on a server

Good to know

The private key must be readable by you only: ssh refuses it with "UNPROTECTED PRIVATE KEY FILE" otherwise (chmod 600).
The first time, ssh asks you to trust the server's fingerprint and remembers it in ~/.ssh/known_hosts.