What is 750 permission in Linux?

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Managing file and directory permissions in Linux is crucial for maintaining security and proper access control. The chmod command allows you to change these permissions. This guide will explain what chmod 750 means, ensuring clear and practical understanding.

What Does chmod 750 Mean?

When you set permissions to 750 using chmod, it translates to:

  • User (Owner): Read (4) + Write (2) + Execute (1) = 7
  • Group: Read (4) + Execute (1) = 5
  • Others: No permissions = 0

In summary, chmod 750 gives full access (read, write, and execute) to the owner, read and execute permissions to the group, and no permissions to others.

Breaking Down chmod 750

To understand chmod 750, let’s break it down by each digit:

  1. First Digit (7): Permissions for the user (owner)
  • Read (4): The user can read the file/directory.
  • Write (2): The user can modify the file/directory.
  • Execute (1): The user can execute the file or navigate into the directory. Total: 4 + 2 + 1 = 7
  1. Second Digit (5): Permissions for the group
  • Read (4): Group members can read the file/directory.
  • Execute (1): Group members can execute the file or navigate into the directory. Total: 4 + 1 = 5
  1. Third Digit (0): Permissions for others
  • No permissions are granted to others.

Applying chmod 750

To set permissions to 750, you use the chmod command followed by the desired permission and the path to the file or directory.

Command:

chmod 750 /path/to/file_or_directory

Explanation:

  • chmod: The command to change file and directory permissions.
  • 750: Sets read, write, and execute permissions for the user, read and execute permissions for the group, and no permissions for others.
  • /path/to/file_or_directory: The path to the file or directory you want to modify.

Example Usage

Example 1: Setting chmod 750 for a Directory

chmod 750 /path/to/important_directory
  • This command ensures that only the owner has full control, the group can read and execute, and others have no access.

Example 2: Setting chmod 750 for a File

chmod 750 /path/to/script.sh
  • This command allows the owner to read, write, and execute the script, the group to read and execute it, and prevents others from accessing it.

Verifying Permissions

After applying chmod 750, you can verify the permissions using the ls -l command.

Example:

ls -l /path/to/important_directory

Output:

drwxr-x--- 2 user group 4096 Jan  1 12:00 important_directory

Explanation:

  • drwxr-x---: Indicates read, write, and execute permissions for the owner, read and execute permissions for the group, and no permissions for others.

Security Considerations

Setting chmod 750 is a good practice for directories and files that should be accessed only by the owner and certain group members. It prevents unauthorized access by others, enhancing the security of sensitive files and directories.

Common Use Cases

  • Private Directories: Use chmod 750 for directories containing sensitive information that only the owner and trusted group members should access.
  • Scripts and Executables: Use chmod 750 for scripts and executables that the owner can modify, and the group can execute, but others should not access.

Conclusion

Understanding and using chmod 750 helps maintain security and proper access control in your Linux system. By setting read, write, and execute permissions for the owner, read and execute permissions for the group, and no permissions for others, you ensure that sensitive files and directories are protected from unauthorized access. This approach helps safeguard your system and maintains a balance between usability and security.