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tamilvanan
tamilvanan

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Learn Linux - 002

#linux #programming #cli #terminal

Note: I’m not an expert. I’m writing this blog just to document my learning journey. 🚀

🚀 What is Linux?

✅ First Principles:

Linux is an operating system — the core software that lets you control a computer’s hardware, run programs, and manage files.

Just like Windows or macOS, Linux:

  • Boots the system
  • Manages memory and processes
  • Lets you open programs, connect to the internet, and store files

But Linux is different:

  • It's open source (you can see and change its code)
  • It’s modular and customizable
  • It’s used widely in servers, cybersecurity, embedded systems, and more

🧠 Why Learn Linux?

  • Most servers and cloud machines run Linux
  • Most CTFs, ethical hacking, and development tools are built for Linux
  • Learning Linux teaches you how computers really work

🧱 Linux Structure (What It's Made Of)

Linux has 4 major layers:

  1. Kernel
    The core of Linux. It talks to the hardware (CPU, memory, devices).

  2. Shell
    The command-line interface (like Bash or Zsh). You type commands here.

  3. Filesystem
    A hierarchy of folders/files starting from / (called "root").

  4. User space
    All the programs you run: browsers, editors, servers, etc.

📁 Linux Filesystem: Not C:\ Drive

In Linux, everything is a file or directory. There's no "C drive".

/
├── bin       → essential commands
├── home      → users' personal files
│   └── yourname/
├── etc       → config files
├── var       → logs, variable data
├── tmp       → temporary files
├── usr       → user programs and libraries
└── root      → root user’s home
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🔤 Basic Commands (with Meaning)

Here are essential Linux commands — not just what they do, but why.

📂 File Navigation 

pwd           # print working directory
cd /path/     # change directory
ls            # list files
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📁 Working with Files 

touch file.txt          # create a new empty file
mkdir newfolder         # make a directory
rm file.txt             # delete a file
rmdir folder            # delete a folder
mv old.txt new.txt      # rename or move
cp file.txt copy.txt    # copy files
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📄 Viewing Content 

cat file.txt      # show file contents
less file.txt     # view long files
head file.txt     # first 10 lines
tail file.txt     # last 10 lines
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👤 Linux Users and Permissions

Users

  • root: superuser with full power
  • Regular users: limited power, safer

Permissions

Every file has:

  • Owner, Group, and Others
  • Read (r), Write (w), Execute (x) permissions 
ls -l
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Example:

-rwxr-xr--  1 user group 1234 file.sh
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Means:

  • Owner can read/write/execute
  • Group can read/execute
  • Others can only read

🔧 Installing Software (Debian/Ubuntu style) 

sudo apt update
sudo apt install nmap
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  • sudo: run as root
  • apt: package manager
  • install: download and setup software

🧠 Mental Model: Everything Is a Command

In Linux:

  • You don’t click — you command
  • Even graphical apps are wrappers around terminal commands
  • You gain power through understanding, not clicking

✅ Summary: What You Should Know Now

Concept Why It Matters
Linux is modular You can control and customize everything
Shell & terminal Interface to run commands, scripts
Filesystem Understand where everything lives
Permissions Secure access and prevent errors
Package manager Easily install/update/remove tools

Top comments (1)

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alexahayes profile image
Alexa Hayes •

Amazing!