Linux is a free and open-source operating system based on Unix. It is widely used in servers, cloud, and DevOps because it is stable, secure, and fast.

Key Features of Linux

• Open Source - Source code is free and publicly available; anyone can modify it
• Multi-User - Multiple users can work at the same time, each with separate permissions
• Multi-Tasking - Runs multiple processes simultaneously with efficient CPU and memory usage
• Security - Strong file permissions (read, write, execute), user-based access control, less prone to viruses
• Stability - Runs for long periods without rebooting; preferred for servers and production systems
• Portability - Runs on different hardware: mobiles, servers, cloud, IoT, supercomputers
• CLI (Command Line Interface) - Powerful terminal control; easy automation using shell scripts (important for DevOps)
• Networking - Built-in support for TCP/IP, SSH, FTP, HTTP; used as base OS for network servers
• File System - Supports ext4, xfs, nfs, and more; everything is treated as a file
• Free - No license cost; reduces infrastructure expenses

Virtualization

Virtualization is the process of creating virtual versions of physical hardware — allowing multiple virtual machines (VMs) to run on one physical machine.

How It Works (Flow) - type 2 flow

Applications  // running app in VM
     ↓
Guest OS (Linux / Windows)   // OS inside VM
     ↓
Virtual Machine   // version of CPU, Memory and all
     ↓
Hypervisor    // Brain of VM
     ↓
Host OS (only in Type-2, optional)
     ↓
Physical Hardware

Key Components

• Physical Hardware - Actual machine: CPU, RAM, Disk, Network Card