SSH

SSH, or Secure Shell, is a protocol used to securely log onto remote systems. It is the most common way to access remote Linux and Unix-like servers.

Installation

The client software is part of the default Ubuntu installation.

Generating a new SSH key

Check for existing SSH keys:

ls -al ~/.ssh

Generate a new SSH key:

ssh-keygen -t rsa -b 4096 -C "you@example.com"

Add your SSH key to the ssh-agent:

eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_rsa

Permissions

If you copied your keys from another computer, permissions should be like this:

chmod 700 ~/.ssh
chmod 644 ~/.ssh/authorized_keys
chmod 644 ~/.ssh/known_hosts
chmod 644 ~/.ssh/config
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub

SSH Config File

You probably log in and out of a half dozen remote servers on a daily basis. You can add a config file ~/.ssh/config to simplify your life. For example:

Host dev
    HostName dev.example.com
    Port 22000
    User william

And then, just:

ssh dev