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Linux Basics for Developers

Linux is an open-source operating system. In DevOps, we rarely use a mouse or a graphical interface; we interact with Linux through the CLI (Command Line Interface).

Why Linux?

Linux is the backbone of the internet. Most servers run on Linux because it's stable, secure, and free. As a developer, knowing how to navigate and manage Linux is essential for deploying and maintaining your applications.

1. The Linux File System​

Unlike Windows (C:, D:), Linux uses a single unified tree structure. Everything starts from the Root directory, represented by a forward slash /.

  • /bin & /usr/bin: Where standard programs (commands) live.
  • /etc: Where configuration files are stored (the "Settings" of Linux).
  • /home: Where user files live (e.g., /home/ajay).
  • /var/log: Where your application logs are kept (crucial for debugging!).

2. Essential Navigation Commands​

You need to move through the server like a pro. Here are your "Master" keys:

  • pwd: Print Working Directory (Where am I right now?).
  • ls: List files in the current folder. (Use ls -la to see hidden files).
  • cd: Change Directory.
    • cd .. (Go up one level).
    • cd ~ (Go to your home folder).
  • clear: Cleans up your terminal screen.

3. File & Folder Manipulation​

Managing your source code and logs directly on the server:

  • mkdir <name>: Create a new folder.
  • touch <file>: Create a new empty file.
  • cp <source> <dest>: Copy files.
  • mv <source> <dest>: Move or Rename files.
  • rm <file>: Remove a file. (Be careful: there is no "Recycle Bin" in Linux!).
  • rm -rf <folder>: Forcefully delete a folder and everything inside it.

4. Permissions & The "Sudo" Power​

Linux is built on security. Every file has an owner and specific permissions.

  • Read (r), Write (w), and Execute (x).
  • sudo: Stands for "SuperUser Do." It allows you to run commands with administrative privileges.
warning

With sudo, you have the power to delete the entire operating system. Use it only when necessary!

5. Viewing and Editing Files​

Sometimes you need to check a log file or change a .env variable without a code editor.

  • cat: Dumps the entire file content into the terminal.
  • tail -f: Watches a file in real-time (Perfect for watching server logs!).
  • nano: A simple, beginner-friendly text editor inside the terminal.
  • vim: The "Master" editor. It has a steep learning curve but is incredibly fast once mastered.

6. Pipes and Redirection​

This is where Linux becomes a superpower. You can take the output of one command and send it to another using the "Pipe" |.

  • ls -la | grep "config": List all files but only show the ones with "config" in the name.
  • cat logs.txt > output.txt: Save the content of a file into a new one.

Practice: The Terminal Challenge​

  1. Open your terminal (or use a Git Bash / WSL if on Windows).
  2. Navigate to your Desktop: cd ~/Desktop.
  3. Create a folder: mkdir codeharbor_test.
  4. Enter the folder and create a file: touch hello.txt.
  5. Write your name into the file: echo "A Master" > hello.txt.
  6. Read it back: cat hello.txt.
Tab Completion

Never type out long file names! Start typing the first few letters and hit the Tab key. Linux will auto-complete the name for you. This is the #1 habit of productive developers.