Lesson 2: Understanding File Permissions

In Linux, everything is a file, and every file has Permissions. This is the heart of Linux security.

The Three Musketeers: Owner, Group, Others

Every file has three types of people who can interact with it:

1. Owner (u): Usually the person who created the file.
2. Group (g): A collection of users with shared access.
3. Others (o): Everyone else on the system.

The Three Powers: Read, Write, Execute

For each type of person, we can grant or deny:

• Read (r): Ability to see the contents.
• Write (w): Ability to change the contents.
• Execute (x): Ability to run the file (if it's a script or program).

Interactive Mission

Let's look at a real-world example. On a server, the /etc/shadow file contains encrypted passwords. Only the root (admin) user should be able to read it.

Steps to Complete:

1. Who are you? Type whoami to confirm you are the root user.
2. Inspect the target: Use ls -l /etc/shadow to see its permissions. You'll see something like -rw-r-----.
3. Create your own secure vault: Create a file named secure.txt and make it so only you can read or write to it using chmod 600 secure.txt.

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