✨ What is Linux? - Linux is an open-source operating system modeled on UNIX. It's the foundation of many cloud infrastructures and has a significant presence in the server world, among other places.
✨ Basic Fundamentals of Linux: - Kernel: It's the core component of the system that interacts with hardware. - Shell: An interface that allows users to interact with the kernel using command lines or scripts.
- File System: Hierarchical structure where all the data is organized.
**Note: Comprehensive Insight into the Linux File System
- Processes: Running instances of programs. Linux treats almost everything as a process.
- User & Groups: Security and permissions are based on users and groups.
✨ The Command Line Interface (CLI)
One of the defining features of Linux is the command line interface or CLI. Unlike graphical user interfaces (GUIs), the CLI requires users to type commands to interact with the system. This might seem intimidating at first, but it offers significant advantages, such as greater control and efficiency.
Common Linux CLI commands:
ls: List files and directories.cd: Change the current directory.mkdir: Create a new directory.touch: Create a new file.cp: Copy files or directories.mv: Move or rename files or directories.rm: Remove files or directories.pwd: Print the current working directory.
✨ File System Hierarchy
Linux organizes files and directories in a hierarchical structure. The root directory is denoted by /, and all other directories and files branch out from there. Understanding this hierarchy is crucial for navigation and proper file management.
Common directories include:
/bin: Essential system binaries./etc: Configuration files./home: User home directories./usr: User-installed software./var: Variable data (e.g., logs)./tmp: Temporary files./dev: Device files.
✨ Users and Permissions
Linux is known for its robust user and permission management system. Each user has a unique username and belongs to one or more groups. File permissions are specified using a combination of read (r), write (w), and execute (x) permissions for the owner, group, and others.
The chmod command is used to change file permissions, while chown is used to change file ownership. Understanding and managing these permissions is crucial for securing your system.
✨ Package Management
Linux distributions come with package management systems that make it easy to install, update, and remove software. For instance, Ubuntu uses apt, while CentOS uses yum. These tools fetch software from online repositories, ensuring that you always have access to the latest updates and security patches.
To install a package, you typically use a command like:
sudo apt-get install package_name
✨ Update and Upgrade
Regular system updates and upgrades are essential to keep your Linux system secure and up-to-date. Use the following commands to perform these tasks:
sudo apt-get update: Update the package lists.sudo apt-get upgrade: Upgrade installed packages.
sudo apt-get dist-upgrade: Upgrade the distribution.
✨ System Information
You can retrieve important system information using various commands, such as:
uname -a: Display system information.df -h: Show disk usage.free -h: Display memory usage.toporhtop: Monitor system processes.
- ls - The most frequently used command in Linux to list directories
- pwd - Print working directory command in Linux
- cd - Linux command to navigate through directories
- mkdir - Command used to create directories in Linux
- mv - Move or rename files in Linux
- cp - Similar usage as mv but for copying files in Linux
- rm - Delete files or directories
- touch - Create blank/empty files
- ln - Create symbolic links (shortcuts) to other files
- cat - Display file contents on the terminal
- clear - Clear the terminal display
- echo - Print any text that follows the command
- less - Linux command to display paged outputs in the terminal
- man - Access manual pages for all Linux commands
- uname - Linux command to get basic information about the OS
- whoami - Get the active username
- tar - Command to extract and compress files in Linux
- grep - Search for a string within an output
- head - Return the specified number of lines from the top
- tail - Return the specified number of lines from the bottom
- diff - Find the difference between two files
- cmp - Allows you to check if two files are identical
- comm - Combines the functionality of diff and cmp
- sort - Linux command to sort the content of a file while outputting
- export - Export environment variables in Linux
- zip - Zip files in Linux
- unzip - Unzip files in Linux
- ssh - Secure Shell command in Linux
- service - Linux command to start and stop services
- ps - Display active processes
- kill and killall - Kill active processes by process ID or name
- df - Display disk filesystem information
- mount - Mount file systems in Linux
- chmod - Command to change file permissions
- chown - Command for granting ownership of files or folders
- ipconfig - Display network interfaces and IP addresses
- traceroute - Trace all the network hops to reach the destination
- wget - Direct download files from the internet
- ufw - Firewall command
- iptables - Base firewall for all other firewall utilities to interface with
- apt, pacman, yum, rpm - Package managers depending on the distro
- sudo - Command to escalate privileges in Linux
- cal - View a command-line calendar
- alias - Create custom shortcuts for your regularly used commands
- dd - Majorly used for creating bootable USB sticks
- whereis - Locate the binary, source, and manual pages for a command
- whatis - Find what a command is used for
- top - View active processes live with their system usage
- useradd and usermod - Add new user or change existing users data
- passwd - Create or update passwords for existing users