Files in Linux:

1. Everything is a File:

   • In Linux, everything is treated as a file, including directories, devices, and even network sockets.

   • This uniformity simplifies interactions with various system components.

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1. File Types:

   • Regular Files: Contain data (text, binary, etc.).

   • Directories: Organize files into a hierarchical structure.

   • Devices: Represent hardware devices (e.g., /dev/sda for the first hard drive).

   • Symbolic Links: Point to other files or directories.

   • Special Files: Represent system resources (e.g., /proc for process information).

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1. File Naming Conventions:

   • Case-sensitive: "File.txt" and "file.txt" are different.

   • Use of special characters: Be cautious with characters like spaces and symbols.

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Linux File Structure:

1. Root Directory (/):

   • Top-level directory containing all other directories and files.

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1. Standard Directories:

   • /bin: Essential binary executables.

   • /etc: Configuration files.

   • /home: User home directories.

   • /var: Variable data (logs, temporary files).

   • /usr: User programs and utilities.

   • /lib: Shared libraries.

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1. Special Directories:

   • /dev: Device files.

   • /proc: Process information.

   • /sys: Kernel and device configuration.

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1. Temporary Directory (/tmp):

   • Temporary files used by applications and users.

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Linux File System Security:

1. File Permissions:

   • Read (r), Write (w), Execute (x):

     • r: View file contents.

     • w: Modify file contents.

     • x: Execute as a program or enter a directory.

   • Permissions for Owner, Group, and Others.

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1. User Ownership (chown):

   • Change the owner of a file or directory.

   • Helps control access to sensitive files.

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1. Root Privileges:

   • Root user (superuser) has unrestricted access.

   • Use sudo to execute commands with root privileges.

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1. File System Hierarchy Standard (FHS):

   • Standardizes file and directory names across distributions.

   • Enhances consistency and predictability.

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1. Mount Points:

   • Different filesystems can be mounted at specific directories.

   • Improves system organization and security.

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1. File Auditing:

   • Some Linux distributions support file auditing.

   • Tracks file access and modifications for security monitoring.

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1. File Encryption:

   • Encryption tools (e.g., LUKS) can secure entire filesystems or individual files.

   • Adds an extra layer of protection for sensitive data.

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The Linux file system, with its uniform treatment of everything as a file and a well-organized structure, contributes to the security and stability of the operating system. Understanding and managing file permissions play a crucial role in securing the Linux environment. 🛡️🐧

Some Useful commands while working with the Linux files.

1. Viewing a file's content (cat, less, more):

   • cat filename: Displays the entire content of a file.

   • less filename or more filename: Allows you to navigate through large files interactively.

    cat fruits.txt

1. Changing file permissions (chmod):

   • chmod permissions filename: Changes the access permissions of a file.

    chmod 755 filename

1. Checking command history (history):

   • history: Displays a list of recently executed commands.

    history

1. Removing a directory (rmdir, rm -r):

   • rmdir directory_name: Removes an empty directory.

   • rm -r directory_name: Removes a directory and its contents.

    rmdir my_directory

1. Creating and viewing files (touch, echo, cat):

   • touch filename: Creates an empty file.

   • echo "content" > filename: Adds content to a file.

   • cat filename: Displays the content of a file.

    touch fruits.txt
    echo "Apple\nMango\nBanana\nCherry\nKiwi\nOrange\nGuava" > devops.txt

1. Displaying top and bottom lines (head, tail):

   • head -n 3 filename: Displays the top three lines of a file.

   • tail -n 3 filename: Displays the bottom three lines of a file.

    head -n 3 fruits.txt
    tail -n 3 fruits.txt

1. Creating and comparing files (touch, diff):

   • touch filename: Creates an empty file.

   • diff file1 file2: Shows the differences between two files.

    touch Colors.txt
    diff fruits.txt Colors.txt

Text Editors in Linux:

1. Vim:

   • vim filename: Opens the Vim editor for the specified file.

   • Press i to enter insert mode, make changes, then press Esc and :wq to save and exit.

    vim filename

1. Nano:

   • nano filename: Opens the Nano editor for the specified file.

   • Use arrow keys to navigate, make changes, then press Ctrl + X, Y, and Enter to save and exit.

    nano filename

File Permissions in Linux:

1. File Permissions:

   • File permissions in Linux are represented by three sets of characters: owner, group, and others.

   • Each set consists of three characters: r (read), w (write), and x (execute).

2. Changing File Ownership (chown):

   • chown new_owner:new_group filename: Changes the owner and group of a file.

    chown user1:group1 fruits.txt

1. Manipulating File Permissions (chmod):

   • chmod +permission or chmod -permission: Adds or removes a specific permission.

   • chmod ugo+rw filename: Gives read and write permissions to owner, group, and others.

    chmod +x script.sh

These commands and concepts form a foundation for working in a Linux environment, especially within the context of your DevOps journey. Feel free to experiment with these commands in your terminal to gain hands-on experience! 🚀