Linux Basics: A Comprehensive One-Line Guide to Essential Concepts

Linux is a cornerstone of the IT world, powering servers, desktops, and embedded devices. Whether you're a beginner or brushing up, here's a concise guide covering key Linux concepts with commands to get started.


1. What is Linux?

Linux is an open-source operating system built around the Linux kernel, offering flexibility, stability, and community-driven development.


2. Linux Kernel and Distributions

  • Kernel: The core of Linux, managing hardware and system processes.

  • Distributions: Variants of Linux, such as Ubuntu (sudo apt install), CentOS (yum install), and Fedora (dnf install).


3. Linux Filesystem

  • Structure: Hierarchical organization starting at /.

  • Key Directories:

    • /home (user files)

    • /etc (configuration files)

    • /bin (essential commands like ls, cp)

  • Command: ls / to view root directories.


4. User Management

  • Create a user: sudo useradd username

  • Change password: sudo passwd username

  • Check current user: whoami

  • File permissions: chmod u+x filename to grant execution permission to the user.


5. Command Line Basics

  • Navigate: cd /path/to/directory

  • List files: ls -l

  • Create directory: mkdir myfolder

  • Copy files: cp source.txt destination/


6. Process and Job Management

  • Check running processes: ps aux

  • Monitor system: top

  • Kill a process: kill PID (replace PID with the process ID from ps).

  • Background job: Run command & to execute a job in the background.


7. Package Management

  • Ubuntu/Debian: sudo apt update && sudo apt install packagename

  • CentOS/RHEL: sudo yum install packagename

  • Fedora: sudo dnf install packagename

  • List installed packages: dpkg -l or rpm -qa.


8. Networking Essentials

  • Ping a server: ping google.com

  • Check network interfaces: ifconfig or ip addr

  • Network connections: netstat -tuln


9. Shell Scripting

  • Create a script: Use a text editor (e.g., nano script.sh) and start with #!/bin/bash.

  • Example:

#!/bin/bash
echo "Hello, Linux!"

10. Security

  • File ownership: chown user:group filename

  • View permissions: ls -l

  • SSH into a server: ssh user@hostname

  • Basic firewall setup: sudo ufw enable and sudo ufw allow 22 (allow SSH).


11. Conclusion

Mastering Linux requires practice, and these concepts form the foundation for advanced topics like DevOps and Cloud Computing. Start experimenting with these commands to deepen your understanding.