Day 1: Introduction to Linux & Shells

🔹 What is Linux?

• Linux is an open-source operating system (like Windows or macOS).
• Unlike Windows, Linux is command-line friendly and used widely in:
  • Servers & Cloud (AWS, Azure, GCP)
  • DevOps & SRE (automation, monitoring)
  • Cybersecurity (ethical hacking, SOC)

👉 Every Linux distribution (Ubuntu, Fedora, CentOS, Debian, etc.) shares the same basic commands.

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🔹 What is a Shell?

• A shell is a program that lets you talk to the operating system by typing commands.
• Think of it as a translator between you and the kernel.
• Common shells:
  • bash (most popular, default in many distros)
  • zsh (modern, customizable)
  • fish (user-friendly)

👉 You can check which shell you’re using:

echo $SHELL

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🔹 First Linux Commands to Try

whoami       # Shows your current username
pwd          # Prints current working directory
ls           # Lists files in current directory
uname -a     # Shows system, kernel & architecture info

👉 Example run:

$ whoami
t3p_user

$ pwd
/home/t3p_user

$ ls
Desktop  Documents  Downloads

$ uname -a
Linux ubuntu 5.15.0-78-generic #85-Ubuntu SMP x86_64 GNU/Linux

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🔹 Pro Tips

• Case-sensitive: LS ≠ ls.
• Use the man command for help: man ls
• Use clear to clean the terminal screen.

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📖 Learning Resources

• Linux Journey (Free Interactive Learning)
• Linux Command Handbook by FreeCodeCamp
• Practice in a browser: JSLinux Online Emulator

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✅ By the end of Day 1, you should:

• Know what Linux & Shell are.
• Run 4 basic commands (whoami, pwd, ls, uname).
• Be comfortable exploring with man pages.