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Introduction

In Linux, each file and directory has a specific set of permissions that control the actions users can perform on it. These permissions determine who can read, write, or execute a file/directory. Understanding and correctly setting these permissions is crucial for maintaining system security and functionality.

Prerequisites

• Basic knowledge of Linux command line
• Access to a Linux system for practicing commands
• Familiarity with the concept of users and groups in Linux

Understanding Permissions

Permissions in Linux are represented by a three-digit code, with each digit reflecting the permissions set for the file’s owner, the group, and others (public), respectively. Here’s a breakdown of what each digit represents:

• 0: No permission
• 1: Execute
• 2: Write
• 3: Write and execute
• 4: Read
• 5: Read and execute
• 6: Read and write
• 7: Read, write, and execute

Example: Setting Permissions

For instance, a file with permissions set to 754 implies the following:

• The Owner can read, write, and execute the file.
• The Group can read and execute the file.
• The Public can only read the file.

Common Permission Levels

Understanding common permission levels helps in setting appropriate permissions for different types of files and directories.

Files

• 600: Makes a file inaccessible to everyone except the owner.
• 644: Readable by everyone, suitable for files like HTML documents.
• 666: File can be read and modified by everyone, used for files that might be modified by scripts.
• 755: File can be read and executed by everyone, common for scripts.
• 777: Writable and executable by everyone, not recommended due to security concerns.

Directories

• 711: Files within the directory can be executed by everyone, but the directory contents cannot be listed.
• 755: Files and contents of the directory can be seen and executed by everyone, standard for web directories.
• 777: Allows full read/write/delete access to everyone, not recommended for security reasons.

Conclusion

Understanding and correctly setting file permissions is crucial for securing your Linux system. By using the permission codes , you can ensure that files and directories have the appropriate level of accessibility, thus protecting your system from unauthorized access.

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