Module 2

1. The All-Powerful "Root" and sudo

The Root user is the god-mode account. It can delete the entire operating system with one command. Because that's dangerous, we use sudo (SubUser DO).

Command: sudo [command]

Analogy: It’s like a security guard giving you a temporary master key. You perform one task, then give the key back.

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2. Understanding Permissions (ls -l)

When you run ls -l, you see a string like this: -rwxr-xr--

This string is broken into three sets of three:

• User (Owner): What the person who owns the file can do.
• Group: What members of the file's assigned group can do.
• Others: What everyone else on the system can do.

The Letters:

• r (Read): Can view the file.
• w (Write): Can edit/delete the file.
• x (Execute): Can run the file (like a program or script).

3. Changing Permissions (chmod)

You change permissions using the chmod command. The easiest way is using numbers:

• 4 = Read
• 2 = Write
• 1 = Execute

You add them together to get the permission level.

• 7 (4+2+1) = Full access (rwx) 5 (4+0+1) = Read & Execute (r-x) 6 (4+2+0) = Read & Write (rw-) Example: chmod 755 myfile.txt (Owner gets 7, Group gets 5, Others get 5). 4. Managing Users sudo useradd [name]: Creates a new user. sudo passwd [name]: Sets the password for that user. sudo chown [user]:[group] [file]: Changes who owns the file.

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  Module 2 Practical Challenge

  This is where you act like a real System Administrator. Create a New Identity: Create a user named app_user. Give them a password. The Secret Folder: Create a directory in /home called top_secret. Lock it Down: Change the ownership of top_secret so it belongs to app_user. Restrict Access: Change the permissions (chmod) so that app_user can do everything (7), but nobody else on the system (group and others) can even see inside the folder (00). Hint: The command will look like sudo chmod 700 /home/top_secret Test It: Try to cd into that folder as your regular user. You should get a "Permission Denied" error. Then try sudo cd (or sudo ls) to see if the "master key" works.

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  Continue to Module 3