Short and Crispy

Components of OS

1. Kernel
   • A kernel is that part of the operating system which interacts directly with the hardware and performs the most crucial tasks.
   • Heart of OS/Core component
   • Very first part of OS to load on start-up.
2. User space
   • Where application software runs, apps don’t have privileged access to the underlying hardware. It interacts with kernel.
   • App: GUI, CLI

Software

# Topic covered
* Systems software
* Application software
* Operating System(OS)
* Types of OS
* Multithreading vs Multitasking 

Internet

Since the explosive growth of web-based applications, every developer stands to benefit from understanding how the Internet works. Through this article and its accompanying introductory series of short videos about the Internet from code.org, you will learn the basics of the Internet and how it works. After going through this article, you will be able to answer the following questions:

Git Standard Practices

1. Using .gitignore

Useful .gitignore templates: GitHub

The .gitignore file is a text file that tells Git which files or folders to ignore in a project. A local .gitignore file is usually placed in the root directory of a project. You can also create a global .gitignore file and any entries in that file will be ignored in all of your Git repositories.

1.1 What is version control?

• Version control is a management system that allows you to record and track changes in your source code and files so that you can recall certain versions later.
• It’s like a Google Doc for programming, where you can collaborate with multiple people working on the same code and see the source code’s history

Ultimately, using a version control system allows teams to streamline their development process, which improves their overall efficiency

Command Line Basics Crash Course

Video - https://www.youtube.com/watch?v=cBokz0LTizk

Given above is a quick super-fast course in using the command line. It is intended to be done rapidly in about a day, and not meant to teach you advanced shell usage.

Some Advance unix commands

• crontab, tail, Screen, grep, compress, wc

CRONTAB

• The crontab is a list of commands that you want to run on a regular schedule

# Shows all Crontab
crontab -l

# Edit Crontab
crontab -e

# Remove all cron tab --> Be careful
crontab -r

Unix Intermediate commands

• lsof, kill, ifconfig
• chmod wget
• who whois
• Print user detail

# users name
who

# time of last system boot
who -b

Bread and Butter Commands - all important

• This article provides practical examples of most frequently used commands in Linux/UNIX.

man - Super Important
cd ( Understand flags - dot ., double dot .., tilda~, dash -)
mkdir, mv
cp with recursive flag
ls with different flags
pwd, rm, sudo, apt
touch, cat, less, more
tail, rsync, grep
find - Super Important
sort, date, wc
tree (needs to be installed additionally)

Part 1: Ubuntu Users and Groups

Linux is a multi-user operating system. This means multiple people can be logged in and working on the same system simultaneously, and the system needs a way to differentiate their access.

1. Types of Users

Root User (Superuser):

The King/Queen: This is the most powerful user account (root). It has absolute, unrestricted access to the entire system.

UID 0: The root user always has a User ID (UID) of 0.