⚙️ Day 5: Understanding Linux Processes

A program is static code. A process is that code in action! 🚀

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🧠 Program vs. Process

Term	Definition	State
Program 📄	An executable file stored on the disk.	Passive (Doing nothing)
Process 🏃	A program currently running in memory (RAM).	Active (Executing tasks)

Every active Process has unique identifiers:

1. PID: Process ID (Unique number).
2. USER: Who started it.
3. %CPU: Processor usage.
4. %MEM: Memory usage.
5. COMMAND: The command that started it.

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📚 Key Terminologies

Before we dive into commands, let's clear up some terms:

1️⃣ Terminal vs. Shell

• Terminal: The window/interface where you type.
• Shell: The program interpreting your commands.

2️⃣ Foreground vs. Background

• Foreground: Interactive processes (occupy your terminal).
• Background: Runs silently behind the scenes.

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🕵️‍♂️ Viewing Processes: ps & ps aux

1. Basic View (ps)

Shows only processes running in the current shell session.

ps
# Output shows very few processes (usually just bash and ps itself)

2. Detailed View (ps aux)

The gold standard for viewing system activity.

ps aux
# Shows ALL processes from ALL users

Flags Breakdown:

• a: All users' processes.
• u: Display user/owner information.
• x: Include processes not attached to a terminal (background/daemons).

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📊 Monitoring Live: Task Manager Style

Want to see what's creating load in real-time?

1. The Classic: top

Updates in real-time.

top
# Press 'q' to quit

2. The Modern: htop

Colorful, interactive, and user-friendly. You can even use your mouse! 🖱️

htop
# A visual upgrade to top

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🔐 Processes & Ownership

Who controls the process?

Rule: You can only kill or manage processes you own (unless you represent the "Bank", i.e., root).

• kali (User): Can control/kill processes owned by kali.
• root (Admin): Can control ANY process.
• Other Users: Cannot touch your processes.

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