Understanding Operating Systems (Theory & Hands-on)

🟢 1. What is an OS? How does it manage hardware & software?

An Operating System (OS) is a software layer between the hardware and user applications. It manages:
✅ Hardware: CPU, RAM, Disk, Network, Peripherals.
✅ Software: Applications, Processes, Security, User Interface.

🛠 Hands-on Task: Check OS Details   [ detailed explanation with output and breakdowns : click here ]

✅ Windows: Open Command Prompt (cmd) and run:

cmd

systeminfo

✅ Linux: Open Terminal and run:

bash

uname -a
lsb_release -a

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🟢 2. Types of OS: Windows, Linux, macOS, Unix – Key Differences

Feature	Windows	Linux	macOS	Unix
Source Code	Closed	Open Source	Closed	Open (BSD, AIX)
File System	NTFS, FAT32	EXT4, XFS, Btrfs	APFS	UFS, ZFS
Security	Weak (by default)	Strong	Strong	Strong
User Interface	GUI-Based	CLI & GUI	GUI	CLI & GUI

🛠 Hands-on Task: Find OS Type [ detailes explanation with output and break down : click here ]

✅ Windows:

cmd

echo %OS%

✅ Linux:

bash

cat /etc/os-release

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🟢 3. OS Architecture: Kernel, User Space, System Calls, Libraries

✅ Kernel – Core of the OS (controls hardware). [ for detailed content : click here ]
✅ User Space – Where applications run. [ for detailed content : click here ]
✅ System Calls – Bridge between user space & kernel. [ for detailed content : click here ]
✅ Libraries – Pre-written code apps use. [ for detailed content : click here ]

🛠 Hands-on Task: Check Kernel Details [ for detailed explanation with output and breakdown : click here ]

✅ Windows:

powershell

Get-ComputerInfo | Select-Object OsName, OsArchitecture, WindowsVersion, OsBuildNumber

✅ Linux:

bash

uname -r  # Kernel version

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🟢 4. Boot Process

Windows Boot Process

🔹 BIOS/UEFI → MBR/GPT → Bootloader → Kernel Load → Login
✅ Check Boot Configuration in Windows:

cmd

bcdedit

✅ List Startup Services in Windows:

cmd

wmic startup get caption,command

Linux Boot Process

🔹 GRUB → Init/Systemd → Kernel → User Space
✅ Check Boot Logs in Linux:

bash

dmesg | less
systemctl list-units --type=service --state=running

✅ List Systemd Services in Linux:

bash

systemctl list-units --type=service

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🟢 5. Filesystem Structure & Permissions

Windows File System

• Uses NTFS, FAT32.
• Supports ACL (Access Control List) for permissions.

✅ Check File System in Windows:

cmd

fsutil fsinfo drives

✅ Check NTFS Permissions:

cmd

icacls C:\Users\YourUser

Linux File System

• Uses EXT4, XFS, Btrfs.
• File permissions: chmod, chown, umask.

✅ Check Linux File System:

bash

df -Th

✅ Change File Permissions in Linux:

bash

chmod 755 myfile.txt
chown user:group myfile.txt

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🟢 6. Process & Memory Management

Windows:

• Uses Task Manager to monitor processes.
• Virtual Memory (Pagefile.sys) for swapping.

✅ Check Running Processes in Windows:

cmd

tasklist
wmic process list brief

✅ Kill a Process in Windows:

cmd

taskkill /IM notepad.exe /F

Linux:

• Uses Virtual Memory, Paging, Swapping.
• Manage processes with ps, top, htop.

✅ Check Running Processes in Linux:

bash

ps aux
top
htop  # (If installed)

✅ Kill a Process in Linux:

bash

kill -9 <PID>

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🚀 Final Hands-on Tasks (Complete These)

✅ Install Windows 10/11 and Linux (Kali, Ubuntu, Arch) in VirtualBox or VMware.
✅ Experiment with Windows Services:

cmd

sc query
wmic service get name, state

✅ Use Linux Commands:

bash

ls -l
cat /etc/passwd
find / -name "*.conf"
grep "root" /etc/passwd
awk '{print $1}' /etc/passwd
sed 's/root/admin/g' /etc/passwd
tmux new -s hacking-session