Bash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. Bash is a command processor that typically runs in a text window, where the user types commands that cause actions. Bash can also read and execute commands from a file, called a shell script.

bash

GitHub fosters a fast, flexible, and collaborative development process that lets you work on your own or with others.

github

SSH provides a secure way for your to [connect to and authenticate with GitHub's servers](https://help.github.com/en/github/authenticating-to-github/about-ssh). While HTTPS connections use usernames and passwords as credentials, SSH instead uses public and private key pairs. These can be generated on your system using a CLI like [`ssh-keygen`](https://help.github.com/en/github/authenticating-to-github/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent) and then associated with your GitHub account using the public key.

In some cases, you may need to connect to more than one GitHub account from the same system. For example, you may have [separate accounts for personal and professional projects](https://ryanharris.dev/managing-ssh-keys-for-github/), which can be difficult to manage manually. Using `ssh-agent` and a SSH configuration file, you can alleviate this pain point by automatically determining which key to use based on your GitHub repository's `git` URL.

In some cases, you may have multiple GitHub accounts that you need to interact with from the same system. For example, you could have an account for work and another for personal projects, but you don't want to re-authenticate each time you switch between then. By using public SSH keys for each account, you can eliminate this part of the process.

In this lesson, we will create two SSH keys in our terminal using `ssh-keygen` , copy them to our clipboard using `pbcopy` and then add them to our respective GitHub accounts.

Commands we'll be using include:

- `ssh-keygen`
- `ls`
- `pbcopy`

Generate SSH Keys for your GitHub Accounts

In this lesson, we have two local SSH keys: one associated with our personal GitHub account, the other with our work account. 

To more easily manage them, we will use `ssh-add` to add our keys to our system's key manager `ssh-agent`. Then, we will create a SSH configuration file, which will determine what key to use when connecting to GitHub based upon the URL. 

Once we have set up our configuration file, we can test our connections using `ssh -T` and clone repositories with `git clone`.

Commands we will be using in the lesson:

- `ls`
- `ssh-add`
- `touch`
- `ssh`
- `git clone`

Manage Keys with ssh-agent and Add SSH Configuration

When working with multiple GitHub accounts on the same system, you want to ensure that your commits have the proper author information. 

To do this, we'll create a global `git` configuration on our system that uses our personal account's information. Then, in our work-specific repositories, we'll add a local `git` configuration to override our global values.

We will be using the following commands in this lesson:

- `code`
- `git config`

Secure GitHub connections with SSH

Ryan Harris

Course Content