We use Github Enterprise (licensed by Georgia Tech.) for version control of source code, documentation and occasionally useful (small) data files.

This tutorial currently presumes use of a Linux OS (eg. Ubuntu 16.04) and will guide you through:

1. Generating ssh keys & registering them with GT's GitHub Enterprise service
2. Navigating Git 'organizations' and 'repositories' accessible to you
3. Basic commands to clone repositories, pull changed files as well as commit and push your own changes

We prefer that you clone any git repositories via the SSH protocol. This requires you to:

1. generate an ssh public-private encryption key pair for each machine on which you want to clone a repository
2. register your public encryption key with GitHub Enterprise via their browser interface

1. Generate SSH Encryption Key(s):

For each machine on which you want to clone a repository and work with Git version control, you will need to generate an SSH encryption public-private key pair and register the public key with your GitHub Enterprise account.

On the machine (on which you want to clone Git repositories), open a terminal (here we use the Bash shell) and run the following command,

cd ~/.ssh

Note that if the '.ssh/' directory does not exist (eg. using a newly created username/account on the machine), you'll have to create it:

mkdir ~/.ssh
cd ~/.ssh

Now generate your SSH encryption public-private key pair,

ssh-keygen -t rsa -b 4096

It will prompt you for a file name in which to save the generated encryption keys,

Enter file in which to save the key (/home/achang/.ssh/id_rsa): 

As it's possible to have multiple encryption keys for different GitHub services (eg. other than GT's license GitHub Enterprise), you may want to name the file something that identifies it with GT's licensed GitHub Enterprise (eg. 'gatech_github').

Next, you'll be prompted to enter a passphrase/password. Remember your passphrase! When using Git commands that require access to the remote server, you'll be prompted to enter your passphrase.

Enter passphrase (empty for no passphrase):  
Enter same passphrase again: 

Upon completing this, run ls ~/.ssh in the terminal. You should see a pair of files listed with the file name specified earlier; one has the extension .pub (indicating it is the public key) while the other has no extension (and is your private encryption key).

Run, cat <filename>.pub, where <filename> is replaced with the file name you specified for your encryption keys. Copy the output of this command to a text editor. You'll need it in a moment.

Finally, we'll add the private key to the list of encryption keys that the SSH daemon uses,

ssh-add <filename>

Again, replace <filename> with the file name you specified for your encryption keys. Note that you are adding the private key (ie. the filename without the .pub extension).

An example sequence of commands and the expected terminal output is illustrated,

Now that we've generated an SSH public-private encryption key-pair, we need to let GitHub Enterprise know the public key and that it is associated to your account.

In a web browser, go to https://github.gatech.edu. Login using your GT username and password. At the welcome screen/dashboard page, click on the 'identicon' (5×5 pixelated image created from a hash unique to your account) in the upper right. Click 'Settings' from the drop down menu,

Under 'Personal Settings', on the left-hand side, select 'SSH and GPG keys'. Then press the 'New SSH key' button in the top right,

Here, we'll add the public encryption key you previously generated from the terminal,

In the 'Title' field, enter a name for this key. The name should be something indicative of the machine on which this encryption key was generated. You may want to access GT's GitHub Enterprise from multiple machines; each machine will need to have an SSH public encryption key registered here. To distinguish which key belongs to which machine, a suggestion is to include the machine's 'hostname' in the name assigned in the 'Title' field (eg. 'smokescreen_ivalab').

In the 'Key' field, paste the public key contents you previously copied from the command cat <filename>.pub. If you are unsure what text to copy, example text (to copy) is highlighted in the prior image of the Linux terminal. Note that text to be copied will begin with 'ssh-rsa '.