As DevOps engineers, mastering Linux and Git-GitHub is critical for efficient code management and deployment. With a multitude of commands and features at your disposal, having a well-organized cheat-sheet can significantly streamline your workflow. Below, I've compiled a detailed cheat-sheet with essential Linux commands, Git commands, and GitHub tips to enhance your DevOps toolkit.

Linux Commands

File & Directory Management

ls – List directory contents.
Example: ls /home/user lists all files and folders in the /home/user directory.
cd [directory] – Change to a specified directory.
Example: cd /var/log navigates to the /var/log directory.
pwd – Print the current working directory.
Example: pwd might output /home/user/projects.
mkdir [directory] – Create a new directory.
Example: mkdir new_project creates a directory named new_project.
rmdir [directory] – Remove an empty directory.
Example: rmdir old_folder deletes the empty old_folder.
rm [file] – Remove a file.
Example: rm file.txt deletes file.txt.
cp [source] [destination] – Copy files or directories.
Example: cp file.txt /backup/ copies file.txt to the /backup directory.
mv [source] [destination] – Move or rename files or directories.
Example: mv file.txt /archive/ moves file.txt to the /archive directory.
touch [file] – Create an empty file or update its timestamp.
Example: touch newfile.txt creates newfile.txt if it doesn't exist, or updates its timestamp.

File Viewing & Editing

cat [file] – Display the content of a file.
Example: cat README.md shows the content of README.md.
less [file] – View file content page by page.
Example: less largefile.log allows you to scroll through largefile.log.
head [file] – Display the first 10 lines of a file.
Example: head log.txt shows the top 10 lines of log.txt.
tail [file] – Display the last 10 lines of a file.
Example: tail error.log shows the bottom 10 lines of error.log.
nano [file] – Edit a file using the Nano text editor.
Example: nano config.json opens config.json in Nano.
vim [file] – Edit a file using the Vim text editor.
Example: vim script.sh opens script.sh in Vim.

Permissions & Ownership

chmod [permissions] [file] – Change file permissions.
Example: chmod 755 script.sh sets permissions to rwxr-xr-x for script.sh.
chown [owner]:[group] [file] – Change file owner and group.
Example: chown user:admin file.txt changes the owner to user and the group to admin.
ls -l – List files with detailed information, including permissions and ownership.
Example: ls -l displays file details in the current directory.

System Monitoring & Management

top – Display active processes.
Example: top shows real-time process information.
ps aux – List all running processes.
Example: ps aux lists all processes with detailed information.
df -h – Show disk space usage.
Example: df -h displays disk usage in a human-readable format.
du -sh [directory] – Show disk usage of a directory.
Example: du -sh /var displays the size of the /var directory.
free -h – Display memory usage.
Example: free -h shows memory usage in a human-readable format.
uptime – Show system uptime and load averages.
Example: uptime provides the system's uptime and load averages over the last 1, 5, and 15 minutes.

Git Commands

Basic Commands

git init – Initialize a new Git repository.
Example: git init sets up a new Git repository in the current directory.
git clone [url] – Clone a repository from a URL.
Example: git clone https://github.com/user/repo.git clones the repository from the given URL.
git add [file] – Add a file to the staging area.
Example: git add index.html stages index.html for commit.
git commit -m "[message]" – Commit changes with a message.
Example: git commit -m "Add new feature" commits staged changes with the message "Add new feature".
git status – Show the status of changes.
Example: git status displays which files are staged, unstaged, or untracked.
git log – Display commit history.
Example: git log shows a list of recent commits.

Branching & Merging

git branch – List all branches.
Example: git branch lists all branches in the repository.
git branch [branch_name] – Create a new branch.
Example: git branch feature-branch creates a new branch named feature-branch.
git checkout [branch_name] – Switch to a specified branch.
Example: git checkout feature-branch switches to feature-branch.
git merge [branch_name] – Merge a branch into the current branch.
Example: git merge feature-branch merges feature-branch into the current branch.
git rebase [branch_name] – Rebase the current branch onto another branch.
Example: git rebase main rebases the current branch on top of main.

Stashing

git stash – Temporarily save changes without committing.
Example: git stash saves your local changes and reverts to the last commit.
git stash pop – Apply stashed changes and remove them from the stash.
Example: git stash pop re-applies the most recent stash and removes it.
git stash list – List all stashed changes.
Example: git stash list shows all stashed changes.
git stash drop – Remove a specific stash.
Example: git stash drop stash@{0} removes the specified stash.
git stash clear – Remove all stashes.
Example: git stash clear deletes all stashed changes.

Cherry-Picking

git cherry-pick [commit_hash] – Apply a specific commit from another branch.
Example: git cherry-pick 1a2b3c4d applies the commit with hash 1a2b3c4d to the current branch.

Conflict Resolution

git status – Show files with conflicts.
Example: git status identifies files that have conflicts during a merge.
git diff – Show differences between conflicting versions.
Example: git diff shows the changes that need to be resolved.
git add [file] – Stage resolved files for commit.
Example: git add resolved_file.txt stages the resolved file for the next commit.

GitHub Tips

Repository Management

Create a Repository: Click "New" on GitHub and follow the setup prompts.
Fork a Repository: Click "Fork" at the top-right of the repository page to create a personal copy.
Clone a Repository: Use git clone [url] to copy a repository locally.
Example: git clone https://github.com/user/repo.git clones the repository.

Collaboration

Pull Requests: Create a pull request to propose and review changes before merging.
Issues: Track bugs, tasks, and feature requests using GitHub Issues.
Wiki: Use the GitHub Wiki for project documentation.

Branch Protection

Enable Branch Protection: Configure settings to prevent force-pushes and require pull request reviews before merging.

GitHub Actions

Set Up CI/CD: Create workflows in .github/workflows to automate build, test, and deployment processes.

The Ultimate Cheat Sheet for Linux and Git

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