Remote Access with ssh and scp

ssh lets you log in to another computer over the network and work on its command line, with everything encrypted. scp uses the same connection to copy files between computers.

Connecting

ssh [email protected]

Logs in to server.example.com as the user roger. Type exit to disconnect.

ssh -p 2222 [email protected]

Connects to a server that uses a different port.

Logging in with a key instead of a password

SSH keys are more secure than passwords and save you typing. You only need to set them up once.

ssh-keygen -t ed25519

Creates a new key pair in ~/.ssh. Set a passphrase to protect it.

ssh-copy-id [email protected]

Copies your public key to the server so you can log in without a password.

Keep your private key private. Only the file ending in .pub should ever be copied to another computer.

Shortcuts for servers you use often

Add entries to ~/.ssh/config to save typing:

Host myserver
    HostName server.example.com
    User roger
    Port 2222

Now ssh myserver connects with all of these settings.

Copying files with scp

scp report.pdf [email protected]:/home/roger/

Copies report.pdf to the server.

scp [email protected]:/var/log/syslog .

Copies a file from the server to the current directory.

scp -r photos/ [email protected]:~/

Copies a whole folder (-r) to your home directory on the server.

Tunnels

ssh -L 8080:localhost:80 [email protected]

Makes the server's web page available on your computer at http://localhost:8080, through the encrypted connection.

Quick reference

Option	Meaning
`ssh user@host`	Log in to another computer
`-p 2222`	Use a different port
`ssh-keygen`	Create an SSH key
`ssh-copy-id`	Install your key on a server
`scp file user@host:path`	Copy a file to a server
`scp -r`	Copy a folder
`~/.ssh/config`	Save settings for each server