Linux Guide

What is Unix?

Unix comes before linux, so if you know a little bit, it will be great for you. Unix is an operating system whose development started in 1969 for multi-user, multi-tasking. Unix is not free and open source os. It can be only utilized by its copywriters. So linux came into the picture. E.g: SunOS, Solaris, SCO Unix, HP/UX.

What is Linux?

To understand simply, like Windows, Mac, Linux is an operating system [OS] based on Linux Kernel. Operating systems lie between computer hardware and computer users, so that users can interact with computers easily. It was developed by Linus Torvalds in 1991.

It is free and open source means you can use it for free, view its source code. We can change the source code of linux and use it for personal as well as commercial purposes.

E.g: Ubuntu, Arch Linux, Debian GNU etc.

Where is linux?

• TV,
• Mobile Phones.
• Self Driving Car.
• Plane.
• Rocket.
• Many websites are hosted on Linux.

Who Uses Linux?

• US Government
• Top Tech Companies like Google, Microsoft, Amazon by various means.
• Hackers.
• Financial Institutes.
• Computer Programmers and Researchers.
• Those who want to acquire high technical knowledge.

Some Linux Distro:

• Ubuntu
• Fedora
• Elementory OS
• Red Hat OS
• Cent OS
• Kali Linux
• Arch Linux

Linux Vs Windows

• Linux is Free But Windows is Paid.
• Linux runs for months or years without reboot, but in windows often reboot is required.
• Most of the software is available for windows but not in linux.
• Linux is Secure than windows.
• Linux is Fully Customizable but Windows is not.

Points to Remember

• Folder in linux called directory.
• Linux is a case sensitive System. A is different than a.
• Avoid using filename as space.
• Super Admin is also called root who can do anything.
• Software is called a package.

Are all linux based OS free?

No, not all linux based OS are free. Enterprise level linux based operating systems are paid. E.g Red Hat is a paid OS, if we have a problem the Red Hat team will support and provide us a solution.

Basic Tour Of Ubuntu

Background Change, Datetime Settings, Wifi, Bluetooth etc.

Everyday Commands

Command	Meaning
whoami	Your current user name.
hostname	Your current host name.
pwd	Print working directory.
ls	List directory contents.
ls -l	List directory contents in long format.
touch	Create a file.
cat	Concatenate files and print on output i.e. read file.
users	Display currently logged in users.
cp	Copy file. E.g: cp file1.txt file2.txt
mv	Move file. E.g: mv file1.txt file2.txt
mkdir	Create a directory. E.g: mkdir work
rmdir	Remove directory. E.g: rmdir work
rm	Remove files or directory.
rm -R	Remove directory will contain all content.
cd	Change directory.
cd ..	One step back.
touch ch{1..9}.txt	Create file ch1 to ch9.
rm ch*	Delete all files starting from ch.
locate	find your file by name [Fast]. sudo updatedb
sudo	Forcefully do a job.
find	Find or search in file. [Slow]. E.g find -name "brp.txt"
date	Show date and time
sudo reboot	Restart computer
clear	Clear screen

User Management Command In Linux

Command	Meaning
sudo passwd username	Change password of user.
useradd username	Add new user without home directory.
useradd -m username	Add new user with home directory.
userdel username	Delete user without his/her user directory.
userdel -r username	Delete user with his/her user directory.
groupadd groupname	Add new user group.
groupdel groupname	Delete user group.
usermod -aG groupname username	Add user to group.
su username	Switch to specific user.
id username	Display user and group information.

Files

• /etc/passwd => to get user lists.
• /etc/group => to get groups details.
• /etc/shadow => to get hash password.