File Permissions and Access Control Lists

In the Linux world, making sure files and folders are safe and accessible involves understanding something called "file permissions." It's like having a set of rules that determine who can do what with a file.

1. Three User Categories:

   • Owner: This is the person who created the file. They have the most control.

   • Group: Files are part of a group, and members of that group share some access.

   • Others: Everyone else who has access to the system but isn't the owner or in the group.

2. Commands to Change Ownership and Group:

   • To change the owner: chown newowner myfile.txt

   • To change the group: chgrp newgroup myfile.txt

3. Changing Others' Permissions:

   • Use chmod to change permissions. For example, to allow others to read a file: chmod o+r myfile.txt

Task: Changing User Permissions As a task, try changing permissions for the owner using:

$ chmod u+w myfile.txt

This adds write permission for the owner.

File Permissions in Action: Imagine you have a room (file) and keys (permissions). The owner has the master key and can do anything. Group members have their keys to specific doors, and others have a limited set of keys. We use commands to change locks or give more keys.

Access Control Lists (ACL):

• Traditional permissions are like having general keys.

• ACL is like having a fancy key card system where you can specify who can access which rooms.

Commands to Check and Modify ACL:

• To check ACL: getfacl myfile.txt

• To modify ACL (e.g., give specific access to a new user): setfacl -m u:newuser:rw myfile.txt

Conclusion: Linux file permissions are like having rules for who can do what with your files. Changing ownership, group, and permissions helps manage access. Think of it like having keys to different doors. And if you need more detailed control, there's something called Access Control Lists (ACL) for fine-tuning access. Understanding these basics ensures your files are both secure and accessible.