Introduction to Linux Operating System
Kali Linux is a specialized Linux distribution primarily developed as a replacement for Backtrack. It is designed for penetration testing and security auditing. Known for its comprehensive suite of tools that facilitate successful testing tasks.
Backtrack was the precursor to Kali Linux, providing a wide range of tools for penetration testing and advanced security methodologies.
Knoppix is a Debian-based OS, designed to run from CD/DVD or USB. Portable, flexible, ideal for testing and system recovery.
Debian is an open-source OS with the Linux kernel. Known for stability, security, and adherence to free software principles. Many Linux distributions, including Kali, are based on Debian.
Kali Linux evolved from Backtrack with advancements in security tools, usability, and stability.
Kali Linux 1.0 released in 2013, providing advanced tools for security professionals.
Developed by Mati Aharoni and Devon Kearns of Offensive Security.
The kernel is the core program of an OS, managing hardware and software resources.
It decides which running programs get CPU, RAM, and access to peripherals like keyboards, printers, and monitors.
1️⃣ Monolithic Kernel
2️⃣ Micro Kernel
3️⃣ Hybrid Kernel
Controls system resources and manages interactions between hardware and software.
Temporary storage for programs and data. Kernel allocates memory to processes.
Interface to interact with Linux through commands.
-
Bash: Most common, default shell (
$prompt) -
Bourne Shell: Original Unix shell (
/bin/sh) -
Csh: C-like syntax (
%prompt)
Defines directory structure and file placement.
| Directory | Purpose |
|---|---|
| /bin | Essential commands |
| /boot | Boot files |
| /dev | Device files |
| /etc | Configurations |
| /home | User directories |
| /lib | Shared libraries |
| /media | Mount removable media |
| /mnt | Temporary mount points |
| /opt | Optional software |
| /root | Root user's home |
| /sbin | System admin utilities |
| /srv | Service-specific data |
| /tmp | Temporary files |
| /usr | Read-only shared data |
| /var | Variable data, logs |
| /proc | Running process info |
| /lost+found | Recovered file fragments |
| /run | Temporary process storage |
| Type | Description |
|---|---|
- |
Regular file |
d |
Directory |
c |
Character device file |
b |
Block device file |
s |
Local socket file |
p |
Named pipe (FIFO) |
l |
Symbolic link |
-
Regular files:
touch file.txt -
Directory:
mkdir folder -
Local Socket:
/var/run/apache2.sock -
Named Pipe:
mkfifo mypipe -
Symbolic Link:
ln -s target linkname
| Operator | Function |
|---|---|
; |
Execute sequential commands |
& |
Background execution |
&& |
Execute next only if previous succeeds |
# |
Comment |
# Append to a file
echo "Hello World" >> file.txt
# Pipe example
cat file.txt | grep "Hello"