Setting Up Git

Overview

Teaching: 35 min
Exercises: 0 min

Questions

• How do I get set up to use Git?

Objectives

• Configure git the first time it is used on a computer.

• Understand the meaning of the --global configuration flag.

When we use Git on a new computer for the first time, we need to configure a few things. Below are a few examples of configurations we will set as we get started with Git:

• our name and email address,
• to colorize our output,
• what our preferred text editor is,
• and that we want to use these settings globally (i.e. for every project)

On a command line, Git commands are written as git verb, where verb is what we actually want to do. So here is how Dracula sets up his new laptop:

$ git config --global user.name "Vlad Dracula"
$ git config --global user.email "vlad@tran.sylvan.ia"
$ git config --global color.ui "auto"

Please use your own name and email address instead of Dracula’s. This user name and email will be associated with your subsequent Git activity, which means that any changes pushed to GitHub, BitBucket, GitLab or another Git host server in a later lesson will include this information.

Line Endings

As with other keys, when you hit the ‘return’ key on your keyboard, your computer encodes this input. For reasons that are long to explain, different operating systems use different character(s) to represent the end of a line. (You may also hear these referred to as newlines or line breaks.) Because git uses these characters to compare files, it may cause unexpected issues when editing a file on different machines.

You can change the way git recognizes and encodes line endings using the core.autocrlf command to git config. The following settings are recommended:

On OS X and Linux:

$ git config --global core.autocrlf input

And on Windows:

$ git config --global core.autocrlf true

You can read more about this issue on this GitHub page.

For these lessons, we will be interacting with GitLab @ UW-Madison and so the email address used should be the same as the one used for your GitLab account.

Dracula also has to set his favorite text editor, following this table:

It is possible to reconfigure the text editor for Git whenever you want to change it.

Exiting Vim

Note that vim is the default editor for many programs. If you haven’t used vim before and wish to exit a session, type Esc then :q! and Enter.

Git (2.28+) allows configuration of the name of the branch created when you initialize any new repository. Dracula decides to use that feature to set it to main so it matches the cloud service he will eventually use.

$ git config --global init.defaultBranch main

Default Git branch naming

Source file changes are associated with a “branch.” For new learners in this lesson, it’s enough to know that branches exist, and this lesson uses one branch.
By default, Git will create a branch called master when you create a new repository with git init (as explained in the next Episode). This term evokes the racist practice of human slavery and the software development community has moved to adopt more inclusive language.

In 2020, most Git code hosting services transitioned to using main as the default branch. As an example, any new repository that is opened in GitHub and GitLab default to main. However, Git has not yet made the same change. As a result, local repositories must be manually configured have the same main branch name as most cloud services.

For versions of Git prior to 2.28, the change can be made on an individual repository level. The command for this is in the next episode. Note that if this value is unset in your local Git configuration, the init.defaultBranch value defaults to master.

The five commands we just ran above only need to be run once: the flag --global tells Git to use the settings for every project, in your user account, on this computer.

You can check your settings at any time:

$ git config --list

You can change your configuration as many times as you want: just use the same commands to choose another editor or update your email address.

SSH Background and Setup

Before Dracula can connect to a remote repository, he needs to set up a way for his computer to authenticate with GitLab so it knows it’s him trying to connect to his remote repository.

We are going to set up the method that is commonly used by many different services to authenticate access on the command line. This method is called Secure Shell Protocol (SSH). SSH is a cryptographic network protocol that allows secure communication between computers using an otherwise insecure network.

SSH uses what is called a key pair. This is two keys that work together to validate access. One key is publicly known and called the public key, and the other key called the private key is kept private. Very descriptive names.

You can think of the public key as a padlock, and only you have the key (the private key) to open it. You use the public key where you want a secure method of communication, such as your GitLab account. You give this padlock, or public key, to GitLab and say “lock the communications to my account with this so that only computers that have my private key can unlock communications and send git commands as my GitLab account.”

What we will do now is the minimum required to set up the SSH keys and add the public key to a GitLab account.

The first thing we are going to do is check if this has already been done on the computer you’re on. Because generally speaking, this setup only needs to happen once and then you can forget about it.

Keeping your keys secure

You shouldn’t really forget about your SSH keys, since they keep your account secure. It’s good practice to audit your secure shell keys every so often. Especially if you are using multiple computers to access your account.

We will run the list command to check what key pairs already exist on your computer.

ls -al ~/.ssh

Your output is going to look a little different depending on whether or not SSH has ever been set up on the computer you are using.

Dracula has not set up SSH on his computer, so his output is

ls: cannot access '/c/Users/Vlad Dracula/.ssh': No such file or directory

If SSH has been set up on the computer you’re using, the public and private key pairs will be listed. The file names are either id_ed25519/id_ed25519.pub or id_rsa/id_rsa.pub depending on how the key pairs were set up.
Since they don’t exist on Dracula’s computer, he uses this command to create them.

Create an SSH key pair

To create an SSH key pair Vlad uses this command, where the -t option specifies which type of algorithm to use and -C attaches a comment to the key (here, Vlad’s email):

$ ssh-keygen -t ed25519 -C "vlad@tran.sylvan.ia"

Ed25519 algorithm on legacy system

If you are using a legacy system that doesn’t support the Ed25519 algorithm, use: $ ssh-keygen -t rsa -b 4096 -C “your_email@example.com”

Generating public/private ed25519 key pair.
Enter file in which to save the key (/c/Users/Vlad Dracula/.ssh/id_ed25519):

We want to use the default file, so just press Enter.

Created directory '/c/Users/Vlad Dracula/.ssh'.
Enter passphrase (empty for no passphrase):

Now, it is prompting Dracula for a passphrase. Since he is using his lab’s laptop that other people sometimes have access to, he wants to create a passphrase. Be sure to use something memorable or save your passphrase somewhere, as there is no “reset my password” option.

Note: The unix shell won’t show anything when you type in your password, not even placeholders!

Enter same passphrase again:

After entering the same passphrase a second time, we receive the confirmation

Your identification has been saved in /c/Users/Vlad Dracula/.ssh/id_ed25519
Your public key has been saved in /c/Users/Vlad Dracula/.ssh/id_ed25519.pub
The key fingerprint is:
SHA256:SMSPIStNyA00KPxuYu94KpZgRAYjgt9g4BA4kFy3g1o vlad@tran.sylvan.ia
The key's randomart image is:
+--[ED25519 256]--+
|^B== o.          |
|%*=.*.+          |
|+=.E =.+         |
| .=.+.o..        |
|....  . S        |
|.+ o             |
|+ =              |
|.o.o             |
|oo+.             |
+----[SHA256]-----+

The “identification” is actually the private key. You should never share it. The public key is appropriately named. The “key fingerprint” is a shorter version of a public key.

Now that we have generated the SSH keys, we will find the SSH files when we check.

ls -al ~/.ssh

drwxr-xr-x 1 Vlad Dracula 197121   0 Jul 16 14:48 ./
drwxr-xr-x 1 Vlad Dracula 197121   0 Jul 16 14:48 ../
-rw-r--r-- 1 Vlad Dracula 197121 419 Jul 16 14:48 id_ed25519
-rw-r--r-- 1 Vlad Dracula 197121 106 Jul 16 14:48 id_ed25519.pub

Copy the public key to GitLab

Now we have a SSH key pair and we can run this command to check if GitLab can read our authentication.

ssh -T git@git.doit.wisc.edu

The authenticity of host 'git.doit.wisc.edu (XXX.XX.XXX.XXX)' can't be established.
RSA key fingerprint is SHA256:nThbg6kXUpJWGl7seaGOCspRomTxARLfeviKw6E5SY8.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'git.doit.wisc.edu' (ED25519) to the list of known hosts.
git.doit.wisc.edu: Permission denied (publickey).

Right, we forgot that we need to give GitLab our public key!

First, we need to copy the public key. Be sure to include the .pub at the end, otherwise you’re looking at the private key.

cat ~/.ssh/id_ed25519.pub

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDmRA3d51X0uu9wXek559gfn6UFNF69yZjChyBIU2qKI vlad@tran.sylvan.ia

Copy and paste in the unix shell

Have you tried to use your usual keyboard hotkeys for Copy and Paste in the Unix shell and found they didn’t work?

If you’re using GitBash in Windows, you can copy and paste using your mouse. Highlight the text you want to copy, then right click and select copy. Similarly for paste, right click at the prompt and select paste.

On Windows in GitBash, you can use ctrl + INSERT to copy and Shift + INSERT to paste.

For many users on a mac, the cmd + c and cmd + v work as expected in Terminal.

Linux terminals will vary by distro, but try Shift + ctrl + c and Shift + ctrl + v in Bash.

Now, going to https://git.doit.wisc.edu, click on your profile icon in the top left corner to get the drop-down menu. Click “Preferences,” then on the settings page, click “SSH keys,” on the left side “User settings” menu. Click the “Add new key” button on the right side. Now, paste your SSH key into the “Key” field, then you can add the title (Dracula uses the title “Vlad’s Lab Laptop” so he can remember where the original key pair files are located), and finally click the “Add key” to complete the setup.

Now that we’ve set that up, let’s check our authentication again from the command line.

$ ssh -T git@git.doit.wisc.edu

Welcome to GitLab, @VLAD.DRACULA!

Good! This output confirms that the SSH key works as intended. We are now ready to push our work to the remote repository.

Proxy

If the network you are connected to uses a proxy, there is a chance that your last command failed with “Could not resolve hostname” as the error message. To solve this issue, you need to tell Git about the proxy:

$ git config --global http.proxy http://user:password@proxy.url
$ git config --global https.proxy http://user:password@proxy.url

When you connect to another network that doesn’t use a proxy, you will need to tell Git to disable the proxy using:

$ git config --global --unset http.proxy
$ git config --global --unset https.proxy

Password Managers

If your operating system has a password manager configured, git push will try to use it when it needs your username and password. For example, this is the default behavior for Git Bash on Windows. If you want to type your username and password at the terminal instead of using a password manager, type:

$ unset SSH_ASKPASS

in the terminal, before you run git push. Despite the name, git uses SSH_ASKPASS for all credential entry, so you may want to unset SSH_ASKPASS whether you are using git via SSH or https.

You may also want to add unset SSH_ASKPASS at the end of your ~/.bashrc to make git default to using the terminal for usernames and passwords.

Key Points

• Use git config to configure a user name, email address, editor, and other preferences once per machine.