Tools of the trade - Linux and SQL

###Operating Systems (OS)

The OS serves as the interface between computer hardware and users. It ensures efficiency and ease of use by managing computer operations.

###Key Concepts

Hardware

The physical components of a computer.

Application

A program that performs a specific task.

• >Applications send requests to the OS, which forwards them to the hardware.
• >Hardware communicates back to the OS, which relays information to applications.

Boot Process

When a computer is turned on:

1. >BIOS/UEFI:
   • >BIOS: Prevalent in older systems, it contains loading instructions.
   • >UEFI: A modern replacement for BIOS, more advanced and flexible.
2. >Bootloader: Software that loads the operating system.

Resource Allocation

The OS manages memory and resources to optimize CPU usage across multiple tasks and processes.

Virtual Machines and Virtualization

• >Virtual Machine (VM): A virtual representation of a physical computer.
• >Virtualization: Creating virtual versions of machines using software.

Interfaces

• >User Interface: Allows users to control OS functions.
• >Graphical User Interface (GUI): Uses visual icons (e.g., Start menu, Taskbar).
• >Command Line Interface (CLI): Text-based interaction via commands.

###Linux Overview

An open-source operating system derived from UNIX.

Linux Components

1. >User: Interacts with the system.
2. >Applications: Perform specific tasks.
3. >Shell: Command-line interpreter.
4. >Filesystem Hierarchy Standard (FHS): Organizes data.
5. >Kernel: Manages processes and memory.
6. >Hardware: Physical components.

Popular Linux Distros

1. >

   Red Hat Enterprise Linux (CentOS)

2. >

   Slackware (SUSE)

3. >

   Debian (Ubuntu, Kali Linux)

   

Linux Commands

1. >

   pwd

   : Prints current directory.
2. >

   ls

   : Lists files and directories.
3. >

   cd

   : Changes directory.
4. >

   grep

   : Searches a file for specified strings.
5. >

   mkdir

   : Creates directories.
6. >

   rm

   : Removes files or directories.
7. >

   mv

   : Moves files.
8. >

   chmod

   : Changes file permissions.

File Permissions

• >Types: Read (r), Write (w), Execute (x).
• >Owners: User (u), Group (g), Others (o).

Basic Shells

1. >Bash: Most common.
2. >Zsh: Enhanced features.
3. >Csh/Ksh: Older alternatives.

###Security Analysts and Linux

• >Analyze logs, manage files remotely, and configure permissions.
• >Use commands and tools like

  tcpdump

  , Wireshark, and Metasploit.

###Databases and SQL

Core Concepts

1. >Database: Organized data collection.
2. >Relational Database: Tables connected by relationships.
3. >SQL (Structured Query Language): Interacts with databases.

Key SQL Queries

1. >

   SELECT

   : Returns specified columns.
2. >

   FROM

   : Identifies the table.
3. >

   WHERE

   : Filters results based on conditions.

Joins in SQL

1. >INNER JOIN: Matches rows in multiple tables.
2. >LEFT JOIN: Includes all rows from the first table and matched rows from the second.
3. >RIGHT JOIN: Includes all rows from the second table and matched rows from the first.
4. >FULL OUTER JOIN: Combines all rows from both tables.

###Additional Notes

Penetration Testing Tools

1. >Metasploit: Exploits vulnerabilities.
2. >Burp Suite: Tests web app weaknesses.
3. >John the Ripper: Password cracking.

Linux Package Management

• >A package is software used individually or as part of applications.
• >Package Managers: Tools for installation and management.

###Advanced Commands

1. >

   sudo

   : Temporary elevated privileges.
2. >

   man

   : Detailed documentation for commands.
3. >

   whatis

   : Command summaries.
4. >

   apropos

   : Searches command manuals.

###File System Hierarchy in Linux

• >

  Root (

  /

  ): The top-level directory.

• >

  Organizes directories and subdirectories.

• >

  Example structure:

  

###Conclusion

Linux and its tools provide a flexible environment for various use cases, from development to cybersecurity. Mastering its commands, file systems, and interfaces opens pathways to efficient computing.