What is Linux?

Linux is an open-source operating system written in computer languages like C and other assembly languages. Our smartphones, cars, home appliances, desktops, refrigerators and even thermostats have run on Linux since the mid-1990s, which has now been globally accepted as a reliable and secure operating system. Operating systems (OS) are essential for any device, and Linux is currently the most popular operating system. 

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Linux comprises essential parts necessary to know before learning Linus commands. These are as follows: 

• Bootloader- A Bootloader is software responsible for booting a PC. A Bootloader is present in the boot section of any storage device, which locates and initiates the operating system on the device.
• Kernel- Kernel is the key element inside Linux, managing the entire CPU, memory, and other software, working as a core interface. 
• Init System- The Init system is a subsystem that helps bootstrap user space and controls daemons. In addition, this system is responsible for performing the boot process once initial booting is done and redeemed from the bootloader.
• Daemons- Daemons are background application services like sound, printing etc., managing the background processes rather than being under the user’s direct control.
• Graphical Server- Graphical Server subsystem in Linux displays graphics on the monitor screen. 
• Desktop Environment- A Desktop Environment is the interaction interface of Linux. Desktop Environment extends numerous built-in features like gaming, web browser, configuration tools, settings, etc. In addition, users can choose from various environments like GNOME, Cinnamon, Mate, Pantheon, Enlightenment, etc. 
• Applications- Linux has high-qualified applications installed immediately from a centralised location, just like Ubuntu. In addition, it is user-friendly and includes app store-like tools for easier navigation and configuration.

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The Linux Command Line

A Linux command line is an interface of text input from the user and commands executed by the system. The user has to manually type the commands for it to display on-screen and get executed by OS.

HOW TO USE THE COMMAND LINE?

First, open the Linux command line and pop open a command tool/command prompt by pressing the “CTRL+ALT+T” keys together. 

Logging in to Linux through a tool like PuTTY, will ready the command line on its own. When the command line is opened up, the user might see a prompt like (user@system:~$), which implies the system is ready to execute your commands. 

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IMPORTANT LINUX COMMANDS

The commands can complete all tasks on Linux, and they occur at the interface of the Linux terminal, though these commands are case-sensitive. Press the “CTRL+ALT+T” keys together to open the Linux terminal and execute any command by pressing the “ENTER” key. 

Here are a few important commands to keep in mind while you learn the Linux command line:

LINUX DIRECTORY COMMANDS

• pwd command- Used to display the location of the current directory. Syntax: pwd
• mkdir command- Used to create a new directory under any directory. Syntax: mkdir <directory name>

LINUX FILE COMMANDS

• touch command- Used to create multiple empty files. Syntax: touch <file name> and touch <file 1> <file 2>….<file n>
• cat command- Used to create a file, display its contents, copy the contents, etc. Syntax: cat [OPTION]…[FILE]… etc. Press “CTRL+D” keys together to save the file.

LINUX FILE CONTENT COMMANDS

• head command- Used to display the first ten lines of the contents of a file. Syntax: head <file name>
• tac command- The reverse of the cat command, it displays the file contents from the end. Syntax: tac <file name>

LINUX USER COMMANDS

• su command- Allows administration control from one user to another over Linux. Syntax: su <username>
• id command- Used to display the group ID or the User ID. Syntax: id

LINUX FILTER COMMANDS

• The sed command- Also called the stream editor; it helps in editing files and displays the edited content, without saving any data permanently. Syntax: command | sed’s / <oldWord> / <newWord> /’
• tr command- The tr command is used to translate file content. Syntax: command | tr <’old’> <’new’>

LINUX UTILITY COMMANDS

• The find command- Used to find certain files within the directory. The (.) symbol is used to find current directory names, and the (/) is used to find any roots. Syntax: find. -name “*pdf”
• The date command- Used to find dates, time zones, etc. Syntax: date 

LINUX NETWORKING COMMANDS

• The ip command- Used to assign any IP address or initialise/disable any system interface. Syntax: ip or an ip addr
• The mail command- Used to send emails from the command line. Syntax: mail -s “Subject” <recipient address> 

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