🚀 Shell Scripting Basics: A Beginner's Guide to Linux Commands and Concepts

Switching from Software Testing to DevOps has been an exciting journey—and one of the first major milestones has been learning Linux and Shell Scripting. In this article, I’ll share what I’ve learned so far—from understanding the Linux operating system to writing and executing basic shell scripts using everyday commands.

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🧠 What is an Operating System (OS)?

An Operating System is the software that connects the user with the hardware. It manages everything—from running applications to handling memory, CPU, and devices like printers, keyboards, or disk drives.

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🐧 Why Learn Linux?

Linux is widely used in servers, DevOps tools, cloud platforms, and CI/CD pipelines. Its advantages:

• Efficient device management

• Powerful memory and CPU management

• Great for automation

• Lightweight and open-source

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🧩 What is the Kernel?

The Kernel is the core of any OS, especially Linux. It communicates directly with the hardware. Everything that happens on a system—whether it's allocating memory or scheduling CPU—is managed by the kernel.

Why is it important?
Without the kernel, the OS can’t talk to the hardware. It's like the heart of the system.

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💻 Essential Linux Commands for Beginners

Here’s a quick reference of common Linux commands with their purpose:

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📂 cd, cd .., cd ../..

Used to navigate through directories.

• cd = change directory

• cd .. = go one level up

• cd ../.. = go two levels up

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🗺️ pwd – Print Working Directory

Shows the current directory path you’re in.

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💾 df -h – Disk Free Space

Displays the available disk space in human-readable format (MB/GB).

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📁 ls, ls -ltr – List Files

• ls: lists files in current directory

• ls -ltr: lists with details, sorted by time

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✍️ touch – Create Empty File

Creates a new file without opening it.

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📚 man – Manual Pages

Displays the manual/help for any Linux command. Example: man ls

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📝 vi, vim – Text Editors

• vi: basic text editor in Linux

• vim: improved version with more features

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🏗️ mkdir – Make Directory

Creates new folders/directories.

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🔁 #!/bin/bash – Shebang

Used at the top of shell scripts. Tells the system which interpreter to use (in this case, bash).

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📢 echo – Print to Terminal

Displays a message or variable value. Example: echo "Hello World"

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💾 :wq! – Save and Exit in vi

:wq! = write changes and quit the file (used in vi/vim editors).

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📖 cat – View File Content

Displays the content of files directly in the terminal.

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🚀 sh, ./ – Run Shell Script

• sh script.sh: run using the shell

• ./script.sh: run if the script has execute permissions

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🔐 chmod – Change File Permissions

Gives permission to user, group, or others.

• Permissions:

  • Read = 4

  • Write = 2

  • Execute = 1

Example:
chmod 755 script.sh → gives read, write, execute to user, and read-execute to group and others.

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🕰️ history – Command History

Shows the list of commands you’ve previously run.

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✅ Summary

Mastering basic Linux and shell scripting is the foundation of DevOps. These commands and concepts help you:

• Navigate systems

• Automate tasks

• Write effective scripts

• Work smoothly in cloud/CI/CD environments