CUS 1150 LINUX LECTURE 2

Kernel

Core part of the operating system, acting as a bridge between the software apps and the hardware.

OS Components

Kernel as its core, user interface, file management, network services and various utility applications.

Shell

Facilitates communication between hardware and applications, ensuring efficient and secure multitasking.

Manages system stability and secure access.

Monolithic Kernel

All OS services run in the kernel space, which is fast but has less fault isolation.

Unix, Linux, Open VMS, XTC-400.

Microkernel

Most services moved to user space, allowing for better reliability but more overhead.

Minix 3 and Mach.

Hybrid Kernel

Mixes monolithic and microkernel to allow for speed and better safety.

Windows NT and MacOS.

Nanokernel

Extremely minimal kernel, providing also basic hardware abstraction.

Nemesis and MIT Exokernel projects.

Exokernel

Separates protection and management, gives app direct control over hardware abstractions so apps decide what to build.

Function of Kernel

Process, memory, device, file system, resource, security and access control, and inter process communication management.

Key Points in Kernel

First part of the OS to load at boost, and stays active.

Operates in privileged mode, where user apps can't directly access hardware.

Applications request the kernel via system calls/software interrupts.

Kernel executes requested operation, and returns result to user space.

Context switching as needed to allow multitasking.

Shell

Allows users to interact with the OS by entering commands. Support scripting to automate tasks and provide control over system operations either through the Command Line Shell or the Graphical Shell.

OS vs Kernel

Kernel Input/Output Subsystem

Fundamental component of modern operating systems responsible for managing all input/output operations on a computer.

I/O Request Scheduling

Core responsibility of the I/O subsystem.

Determines order of Execution to improve overall system performance and fair sharing of I/O devices.

Hopes to reduce wait time, response time, and turnaround time.

Maintains a wait queue, and reorder requests to optimize disk access and minimize seek time/latency.

Buffering

Temporary memory area technique used in data transfer to handle speed mismatched between devices and apps for different transfer sizes to allow smooth data flow.

Buffer may exist between two devices or a device and an app.

Roles of UI And Kernel of OS

User can access the kernel or the OS through system calls this is a programmatic way in which a computer program requests a service from the kernel.

User mode cannot access hardware resources, while kernel mode can access hardware like RAM and printer.

Structure of Systems Call

Due to security reasons, user apps cannot access hardware, so it requests the OS through system calls for these.

Monolithic Pros and Cons

Faster process execution and smaller source at the expense of one failure crashing the entire system, not being portable, and its large difficult management size.

Microkernel Pros and Cons

New services can be added without OS modification and kernel process crashes don't crash the whole system, at the cost of more software requirements, complicated process management and difficult to fix messaging bugs.

Hybrid Pros and Cons

No need for testing reboot and faster third-party integration, at the expense of increased bugs due to multi interfaces and difficult module maintenance for some admins.

Nanokernel Pros and Cons

Small footprint and low overhead for high performance, along with high modularity and flexibility for more customization, at the expense of being more complex of a system design.

Exokernel Pros and Cons

High performance and low overhead as user apps can directly control hardware resources and flexibility, at the expense of the kernel having to provide fine-grained control over hardware resources to user apps.

Linux Distribution

OS built on the Linux kernel, bundled with essential software, tools and package managers and customized to serve different users.

Ubuntu

One of the mostly widely used Linux distributions, especially for beginners.

Easy to install, long term support versions and a large software repository.

Used in DevOps, AI and data science environments.

Benefits include no licensing cost, strong community support, high customization and reliable production systems.

Kali Linux

Specifically designed for cybersecurity takes with over 600 security tools for penetration testing, digital forensics, network monitoring, reverse engineering and ethical hacking.

Developed by Offensive Security as a Debian-based open source Linix distribution.

Kali Key Features

1. Preinstalled Security Tools

2. Free and Open Source

3. Cross-Platform and Lightweight

4. Live Boot and Customization directly from a USB

5. Regular Updates with Strong Community Support

Kali Origins

1. Evolved from Backtrack, which was itself based on Ubuntu.

2. Released in March 2013 by Offensive Security as a modern, standardized penetration-testing environment.

3. Base system built on the Debian repository for a balance between stability and cutting-edge features for compatability with tools and hardware.

4. Developed by Offensive Security, experts in penetration testing training.

5. Goal is to offer a complete, ready-to-uze toolkit for ethical hackers.

Debian

Known for stability and is often used as the base for other distributions. Good voice for a solid, secure system without the latest features.

Robust environment for desktops and servers that are mainly used by advanced users and developers.

Layered Structure of Debian OS

1. Hardware

2. Linux Kernel

3. System Utilities

4. Application and Desktop

Debian Hardware

Represents physical components of the computer, like CPU, memory, storage and input/output.

Allows for multiple architectures.

Debian Linux Kernel

Core of the Debian OSm

Manages tasks like memory allocation, process scheduling, file handling, device control and overall resource management.

Debian System Utilties

Includes the APT ( advanced package tool ) package manager, dpkg, system libraries and GNU to provide access to over 59k software packages.

Essential tools for system administration, file management,text processing and package operations.

Debian Applications

Represents user-facing apps, desktop environments ( GNOME, KDE, Xfce ) and third party software.

Underlying layer used to provide web browsing, office productivity, development tools and multimedia.

Debian Free Software Guidelines

Main repository contains only free sofrware, giving users complete freedom to run, study, modify and distribute the software.

Fedora Linux

Linux distribution known for cutting-edge features, modern design, and strong security. Developed by the Fedora Project and sponsored by Red Hat, its mainly used for software development, enterprise systems and general desktop use.

Fedora Uses

Software devs, system admins, cloud computing, containerization and desktop productivity.

Stock Gnome Desktop

Provides clean, modern, unmodified GNOME desktop.

Smooth user friendly experience with a keyboard centric workflow.

Editors in Fedora

1. Workstation

2. Server

3. CoreOS

4. IoT

5. Silverblue

Fedora requires 64-bit Intel CPU, 2 GB minimum RAM, minimum 20 GB free, and 8 GB USB for bootable media.

Arch Linux

Independently developed Linux distribution known for its simplicity, and does not come with pre-installed graphics so you can shape how you want with a DIY approach.

Full control over installed packages, clean and minimal installations, continous updates through rolling release, and extensive documentation through the famous Arch wiki.

Mint

User-friendly and community driven Linux distribution based on Ubuntu, aiming to provide a reliable and elegant operating system with a focus on simplicity.

Features the Cinnamon desktop environment for users transitioning from other operating systems.

Pros of Mint

1. Beginner friendly

2. Good functionality

3. Stability and performance

4. Secure and privacy focused

5. Customization

6. Long Term Support and Updates

Use Case of Linux Distributions

1. Enterprise ( Red Hat, CentOS )

2. Cybersecurity ( Kali Linux )

3. Developers ( Fedora )

4. Multimedia Creation ( Ubuntu )

5. Lightweight and old hardware use ( Lubuntu )

Benefits of Linux

1. Cost Free and Open Source

2. Customizable

3. Secure

4. Resource Efficient

5. Development

6. Diverse Options

7. Stability and Reliability

8. Active Community

Desktop Environments of Fedora

KDE Plasma ( Highly Customizable )

Gnome

Xfce ( Lightweight and Fast )

Lxqt/Lxde ( lightweight old system design )