Operating System Fundamentals, History, Types, and Linux Overview

Operating System Overview

An operating system (OS) is the interface between computer hardware and users (programs or people), managing resources and providing services for applications.

Core Components

Kernel

Device drivers

Process management

Memory management

File system

Network stack

Security mechanisms

Historical Development

Manual processing

Batch processing (online and offline)

Time‑sharing systems

Real‑time systems

OS Classifications

Batch OS

Time‑sharing OS

Personal desktop OS

Server OS

Mobile OS

Parallel and distributed OS

Real‑time OS

Key Functions

Device driver support

Process scheduling and management

Security enforcement

Network protocol handling

Memory allocation and swapping

File system services

GNU/Linux Ecosystem

GNU provides essential tools (gcc, glibc, vi, etc.) while the Linux kernel, originally created by Linus Torvalds in 1991, forms the core. Together they constitute GNU/Linux, distributed under the GPL license.

Licensing Models

GPL (v1, v2, v3) – copyleft, requires derivative works to remain GPL.

LGPL – weaker copyleft, allows linking from proprietary software.

BSD – permissive, permits proprietary derivatives.

Apache – permissive with patent protection.

MIT – minimal restrictions.

Versioning Schemes

Linux kernel versions have evolved from simple incremental numbers (0.01, 0.02 …) to three‑part A.B.C schemes (major.minor.patch) and later to time‑based A.B.C.D formats, where stability is no longer indicated by even/odd numbers.

Linux History and Distributions

From the first 0.01 kernel to modern releases (4.x, 5.x, 6.x), Linux has grown into a foundation for servers, desktops, mobile devices, and supercomputers. Major distributions include:

Red Hat Enterprise Linux (RHEL) and CentOS

Fedora

Debian and Ubuntu (and derivatives like Mint)

openSUSE, SLES

Arch Linux, Gentoo, Slackware

Kali Linux (security testing)

Package Management

RPM (Red Hat, openSUSE) – tools: yum, dnf, zypper DEB (Debian, Ubuntu) – tools: dpkg, apt-get Pacman (Arch Linux)

Portage (Gentoo)

Linux Kernel Features

Portability across architectures (x86, ARM, PowerPC, SPARC, MIPS, etc.)

Extensive network protocol support (TCP/IP, SCTP, high‑speed Ethernet)

Dynamic loadable modules

System call interface for privileged operations

Process and thread management (fork, exec, kill, signal)

Virtual memory with paging and swapping

Virtual File System (VFS) abstraction layer

Role of Linux in Modern IT

Linux powers the majority of web servers, cloud infrastructure, big‑data clusters, high‑performance computing, and many embedded devices. It is also the basis for Android and various virtualization solutions (KVM).

IT Career Paths Related to Linux

Linux system administrator / operations engineer (DevOps, SRE)

Red Hat certification tracks (RHCSA, RHCE, RHCA, etc.)

Software development using C/C++, scripting (Shell, Python), and package building

Source: https://blog.51cto.com/yingyima/2363295