SSH

Secure shell.

SSH lets you log into a terminal on another machine to use the system via the command line.

ssh root@123.12.185.43

SSH Keys

Private/public key pair to encrypt and decrypt traffic sent via ssh.

Generate SSH Keys

ssh-keygen

This will generate private and public key files.

The default key length is 2048 bites. Use -b 4098 for a more secure key.

Check the service you're connecting to for any specific requirements.

SSH Passphrase

Use a passphrase to secure access to your services.

You can revoke the keys if your laptop gets stolen. A passphrase gives you more time to do that before potentially getting compromised.

SSH Agent

Keep your keys in an ssh agent to automatically use them in connections.

eval '$(ssh-agent -s)'
> Agent pid 163858

Once the agent is running, add your key.

ssh-add
> Identity added: /home/user/.ssh/id_rsa (/home/user/.ssh/id_rsa)

SSH Copy ID

Use this command to ssh into a server and copy your pub key. You will be prompted for a password to copy the file, but then will be able to log in without a password.

ssh-copy-id 192.168.1.100

Configuration

Configure ssh targets with an alias for easy access.

~/.ssh/config

Host myhost
 Hostname myhost.com
 User admin
 Port 7822

Access with: ssh myhost.

SCP

Secure Copy Protocol. Copy files via SSH.

Copy file on configured ssh host to current location:
scp HOST:/PATH/TO/FILE .

Some comments on SCP security.