Day 6 : Linux File Permissions

Understanding Linux File Permissions

File permissions in Linux are crucial for securing and managing access to files and directories. Here's a simple explanation of how they work and how you can manage them.

Categories of Users

1. Owner: The user who created the file or directory.

2. Group: A group of users who share similar permissions.

3. Others: All other users on the system.

Permission Types

Each file or directory has three types of permissions:

• Read (r): Allows viewing the content of a file or listing the contents of a directory.

• Write (w): Allows modifying the content of a file or adding/removing files in a directory.

• Execute (x): Allows running a file as a program or entering a directory.

Viewing Permissions

To view the permissions of a file, use the ls -ltr command:

ls -ltr filename

The output will show the permissions in a string like -rwxr-xr--. Here’s a breakdown:

• The first character indicates the type (- for file, d for directory).

• The next three characters (rwx) are the permissions for the owner.

• The middle three characters (r-x) are the permissions for the group.

• The last three characters (r--) are the permissions for others.

Changing Permissions

1. Change Ownership: Use chown to change the owner.

    chown new_owner filename
   

2. Change Group: Use chgrp to change the group.

    chgrp new_group filename
   

3. Change Permissions: Use chmod to change permissions.

    chmod u+rwx filename    # Add read, write, and execute permissions for the owner
    chmod g-w filename      # Remove write permission for the group
    chmod o=r filename      # Set read-only permission for others
   

4. Task Example

5. Create a File:

    touch myfile.txt
   

6. View Permissions:

    ls -ltr myfile.txt
   

7. Change Permissions:

    chmod u+x myfile.txt     # Add execute permission for the owner
    chmod g+r myfile.txt     # Add read permission for the group
    chmod o-r myfile.txt     # Remove read permission for others
   

   View Changes:

    ls -ltr myfile.txt
   

By understanding and using these commands, you can effectively manage who can access and modify your files, ensuring better security and organization within your Linux system.