Git

Git

Git is a distributed version control system that tracks changes to files, enables collaboration through branching and merging, and maintains a complete history of every modification on Linux, macOS, and Windows.

What Git Does and When to Use It

Git records snapshots of file changes in a repository. Every commit stores the state of all tracked files, who made the change, when, and a message describing why. System administrators use Git to version-control server configurations ( /etc/nginx/, /etc/systemd/system/), deployment scripts, Infrastructure as Code (IaC) definitions, and documentation.

Git is distributed — every clone contains the full repository history. This means operations like log, diff, and blame run locally without network access. Remote repositories (on GitHub, GitLab, Bitbucket, or a self-hosted server) serve as central collaboration points, but Git does not require one.

Git is not a backup system. It tracks text-based files efficiently but stores every version in its history, making large binary files problematic. For large binaries, use Git LFS (Large File Storage). For official documentation, see git-scm.com/doc.

How to Install Git

=== "Ubuntu / Debian"

sudo apt install git

=== "RHEL / CentOS / Fedora"

sudo dnf install git

=== "macOS"

Git ships with Xcode Command Line Tools:

xcode-select --install

Configure identity after installation:

git config --global user.name "Your Name"
git config --global user.email "your.email@example.com"

Core Concepts of Git

Git Repository and Working Directory

A Git repository is a directory containing a .git/ subdirectory that holds the commit history, branches, and configuration. The working directory contains the current checked-out version of the files. The staging area (index) holds changes that will be included in the next commit.

Git Branching and Merging

A branch in Git is a lightweight pointer to a commit. The default branch is typically main (formerly master). Creating a new branch copies the pointer — it does not duplicate files. Merging combines the changes from one branch into another. Git performs fast-forward merges when possible and three-way merges when branches have diverged.

Git Remote Repositories

A remote is a reference to a repository hosted elsewhere (e.g., on GitHub or a self-hosted GitLab server). origin is the conventional name for the default remote. git push sends local commits to the remote; git pull fetches and merges remote changes into the local branch.

Common Tasks with Git

How to Initialize a Git Repository

Git creates a new repository in the current directory with git init:

cd /etc/nginx
sudo git init
sudo git add .
sudo git commit -m "Initial commit of Nginx configuration"

How to Clone an Existing Repository with Git

Git downloads a complete copy of a remote repository with git clone:

git clone git@github.com:user/repo.git

How to Stage and Commit Changes with Git

Git tracks changes in two steps — staging ( git add) and committing ( git commit):

git add nginx.conf
git commit -m "Increase worker_connections to 4096"

How to View Commit History with Git

Git displays the commit log with git log. Use --oneline for a condensed view:

git log --oneline --graph --all

How to Create and Switch Branches with Git

Git creates a new branch and switches to it in one command:

git checkout -b feature/ssl-config

Or using the newer switch command:

git switch -c feature/ssl-config

How to Undo the Last Commit with Git

Git removes the last commit but keeps the changes staged with --soft:

git reset --soft HEAD~1

Discard the last commit and all its changes with --hard:

git reset --hard HEAD~1

Git Troubleshooting

Related Tools and Guides

SSH key-based authentication is required for Git operations over SSH (e.g., git@github.com). See the SSH article.

Ansible playbooks and roles should be version-controlled with Git. See the Ansible article.