Knowledge Base

What is Linux?

Linux is an open-source operating system kernel that was first developed by Linus Torvalds in 1991. It later merged with the GNU project to form the Linux distributions we know today. Although Linux is just a kernel, it is often used as a complete operating system along with GNU tools and other open-source software. This combination is often referred to as "Linux."

Key Points:

• Open Source: The source code can be viewed, modified, and distributed by anyone.
• Kernel: Forms the basis of the operating system; provides communication between hardware and software.
• Distribution: A ready-to-use operating system formed by combining the kernel, GNU tools, and other applications.

The main purpose of Linux is to allow users to control and customize their computers. Different distributions cater to different user needs and preferences.

Why is Linux So Popular?

There are many reasons for Linux's popularity:

• Free and Open Source: You don't have to pay any license fees to use Linux. The open source code allows users to modify and customize the system as they wish.
• Security: Linux is quickly updated and patched for security vulnerabilities. Thanks to its open source nature, it is constantly audited by security experts.
• Stability: Linux systems are generally very stable and can run for long periods without restarting.
• Flexibility: Linux can be used on a wide variety of platforms, from desktop computers to servers, embedded systems to mobile devices.
• Community Support: Linux has a large and active community. This community provides support to users, solves problems, and develops new features.
• Performance: Linux uses resources efficiently and generally performs better than Windows or macOS. It is an important reason why it is preferred, especially in server environments.

Real-Life Example: Large companies such as Google, Amazon, and Facebook use Linux in a large part of their infrastructure. These companies are able to serve millions of users thanks to the reliability, performance, and scalability of Linux.

What Does Linux Distribution Mean? Why Are There Different Distributions?

A Linux distribution (distro) is a ready-to-use operating system built on top of the Linux kernel. A distribution includes various components in addition to the kernel, such as GNU tools (e.g., bash, coreutils), a desktop environment (e.g., GNOME, KDE), system services (e.g., systemd), application software (e.g., LibreOffice, Firefox), and installation tools.

The main reasons for having different Linux distributions are:

• Different Target Audiences: Some distributions are aimed at beginners, while others appeal to experienced users. For example, Ubuntu has a user-friendly interface for beginners, while Arch Linux is designed for experienced users who want more customization.
• Different Use Cases: Some distributions are optimized for server use, while others are more suitable for desktop use. For example, CentOS is a popular choice for server applications, while Linux Mint is more suitable for desktop users.
• Different Philosophies: Some distributions adhere more strictly to the free software philosophy, while others support commercial software as well. For example, Debian adheres strictly to free software principles, while Fedora has a more innovative approach and is open to trying the latest technologies.
• Different Package Management Systems: Each distribution uses a different package management system to install, update, and remove software. For example, Debian and Ubuntu use .deb packages, while Fedora and CentOS use .rpm packages. Arch Linux uses its own package management system called pacman.

Step by Step: The Process of Choosing a Linux Distribution

1. Determine Your Needs: What will you use the operating system for? Desktop, server, development environment, etc.
2. Consider Your Experience Level: Are you a beginner or an experienced user?
3. Do Your Research: Learn about different distributions. Read user reviews and make comparisons.
4. Try in a Live Environment: Many distributions can be run in a live environment. This allows you to try the operating system before installing it.
5. Perform the Installation: Install the distribution you have chosen on your computer.

What Are the Main Differences Between Linux Distributions?

The main differences between Linux distributions are:

• Kernel Version: Different distributions use different Linux kernel versions. Newer kernel versions generally offer better hardware support and performance improvements.
• Desktop Environment: Distributions come with different desktop environments. Different desktop environments such as GNOME, KDE, XFCE, LXDE have different appearances, features, and resource consumption.
• Package Management System: Distributions use different package management systems to install, update, and remove software. Different package management systems such as APT (Debian/Ubuntu), RPM (Fedora/CentOS), Pacman (Arch Linux) use different commands and tools.
• System Services: Distributions use different system initialization systems to manage system services. Different system initialization systems such as Systemd, SysVinit, Upstart control how the system is started and which services are started.
• Default Applications: Distributions come with different applications by default. For example, Ubuntu usually comes with LibreOffice and Firefox, while Fedora usually comes with GNOME and Firefox.
• Community Support: Each distribution has its own community. Some distributions have larger and more active communities, while others have smaller and more niche communities.

How to Use Command Line (Terminal) in Linux? What are the Basic Commands?

The command line (terminal) in Linux is a text-based interface. The command line is a powerful and flexible way to interact with the system. You can perform many tasks faster and more efficiently than with a graphical interface.

Basic Commands:

• pwd: Shows the current working directory.
• ls: Lists the files and folders in the current directory. The ls -l command shows detailed information about the files (permissions, size, date, etc.). The ls -a command also shows hidden files.
• cd: Changes the directory. For example, the cd Documents command goes to the Documents folder. The cd .. command goes to the parent directory. The cd ~ command goes to the home directory.
• mkdir: Creates a new directory. For example, the mkdir NewDirectory command creates a directory named NewDirectory.
• rmdir: Deletes an empty directory. For example, the rmdir NewDirectory command deletes the empty directory named NewDirectory.
• rm: Deletes files. For example, the rm file.txt command deletes the file named file.txt. The rm -r directory command deletes the directory and all files within it (use with caution!).
• cp: Copies files or directories. For example, the cp file.txt copy.txt command copies the file named file.txt as copy.txt. The cp -r directory new_directory command copies the directory and all files within it as new_directory.
• mv: Moves or renames files or directories. For example, the mv file.txt new_file.txt command renames the file named file.txt as new_file.txt. The mv file.txt directory command moves the file named file.txt into the directory.
• cat: Displays the content of a file. For example, the cat file.txt command shows the content of the file named file.txt in the terminal.
• less: Displays the content of a file in pages. Useful for large files.
• head: Displays the first few lines of a file. For example, the head -n 10 file.txt command shows the first 10 lines of the file named file.txt.
• tail: Displays the last few lines of a file. For example, the tail -n 10 file.txt command shows the last 10 lines of the file named file.txt. The tail -f file.txt command shows new lines added to the file in real-time (useful for monitoring log files).
• grep: Searches for a specific text within files. For example, the grep "word" file.txt command searches for the word "word" within the file named file.txt.
• sudo: Runs the command with administrator (root) privileges.
• man: Displays help pages about commands. For example, the man ls command shows the help page about the ls command.

Code Example:

# Creating a directory and a file inside it
mkdir documents
cd documents
echo "Hello World!" > file.txt
cat file.txt

These commands create a directory named "documents", navigate into that directory, write the text "Hello World!" to a file named "file.txt", and then display the contents of that file.

How to Ensure Security in Linux? What are the Basic Security Tips?

Linux has a solid foundation in terms of security, but vulnerabilities can occur if it is not configured correctly. Here are some basic security tips to keep your Linux system secure:

• Keep Up-to-Date: Regularly update your operating system and all your applications. Updates close security vulnerabilities and improve performance.
• Use Strong Passwords: Use strong and unique passwords for all user accounts. Passwords should be at least 12 characters long and include uppercase and lowercase letters, numbers, and symbols.
• Enable Two-Factor Authentication (2FA): If possible, enable two-factor authentication for all important accounts. This ensures that your account remains secure even if your password is compromised.
• Disable Unnecessary Services: Disable all services that you do not use. This reduces the attack surface and frees up system resources.
• Use a Firewall: A firewall monitors network traffic and blocks unauthorized access. You can use firewall tools like iptables or ufw in Linux.
• Use the Root Account Carefully: The root account has full authority over the system. Only use the root account when necessary and always protect it with a strong password.
• Take Regular Backups: Back up your data regularly. In the event of an attack or hardware failure, you can restore your data.
• Monitor Logs: Monitor system logs regularly. If you detect abnormal activity, take immediate action.
• Check Software Sources: Only install software from trusted sources. Installing software from unknown or untrusted sources can make your system vulnerable to malware.
• Use SELinux or AppArmor: Security modules like SELinux or AppArmor limit applications' access to system resources. This prevents the entire system from being compromised even if an application is compromised.

Real-Life Example: To secure a web server, a firewall can be configured, unnecessary ports can be closed, SSH access can be secured, and regular security scans can be performed. Additionally, it is important to keep web applications up to date and protected against security vulnerabilities.

What Programming Languages and Development Tools Are Used in Linux?

Linux supports a wide variety of programming languages and development tools for software development. Here are some commonly used programming languages and development tools in Linux:

• C/C++: The Linux kernel and many system programs are written in C/C++. C/C++ is ideal for performance-critical applications. GCC (GNU Compiler Collection) and Clang are commonly used C/C++ compilers on Linux.
• Python: Python is a popular programming language due to its easy-to-learn syntax and extensive library support. It is used in many areas such as web development, data analysis, machine learning, and automation.
• Java: Java is widely used for enterprise applications due to its platform independence and scalability. OpenJDK and Oracle JDK are Java development kits used on Linux.
• JavaScript: JavaScript is used to develop interactive web applications that run in web browsers. Node.js allows JavaScript to be run on the server side.
• PHP: PHP is a widely used scripting language for web development. Many popular content management systems such as WordPress, Drupal, and Joomla are written in PHP.
• Go: Go is a programming language developed by Google that prioritizes performance and concurrency. It is ideal for developing cloud-based applications and network services.
• Ruby: Ruby is a programming language known for its simple and elegant syntax, used for web development. Ruby on Rails is a popular web development framework.
• Shell Scripting: Shell scripting languages such as Bash and Zsh are used to automate system administration tasks.

Development Tools:

• GNU Debugger (GDB): A debugger used to debug C/C++ programs.
• Valgrind: A tool used to detect memory leaks and other memory errors.
• Git: Version control system. Used to track code changes and collaborate.
• Make: A tool used to compile and manage projects.
• Docker: A platform used to run applications in containers.
• Visual Studio Code, Eclipse, IntelliJ IDEA: Integrated development environments (IDEs).

Code Example (Python):

# A simple Python program
def greet(name):
  print("Hello, " + name + "!")

greet("World")

This program prints "Hello, World!".

Case Study: A web development team is developing a web application running on Linux servers. The team is developing the back-end of the application using Python and Django, while developing the front-end using JavaScript and React. They are tracking code changes using Git and running the application in containers using Docker.