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Root User & Sudo

In Linux, not all users are equal. Some have more power than others.

root is the system administrator - User ID: 0

What Details
Home folder /root (not /home/root)
Power No limits, no permission checks
Danger Can delete the entire system

With root you can:

  • Edit/delete any file
  • Install/remove software
  • Create/delete users
  • Change any permission

Why you never log in as root: Older Linux systems required logging in as root. One mistake could destroy everything. Modern Linux locks the root account and uses sudo instead.

Your User Account

When you installed Linux, you created a user (e.g., /home/your-username).

Your user is NOT root. You have limited permissions.

ls /root
# ls: cannot open directory '/root': Permission denied

You can't even look inside /root - that's the root user's personal home folder.

sudo - Superuser DO

sudo lets you run a single command as root.

sudo ls /root
# [sudo] password for your-username:
# (shows files inside /root)
  • Type your user password (not root's password)
  • Linux remembers you for a few minutes so you don't have to retype sudo

Kill sudo timeout

If you want to forget the cached password immediately:

sudo -k

Now the next sudo will ask for password again.

Check who you are

whoami        # your-username
sudo whoami   # root (sudo changes who you are temporarily)

id            # your user ID (UID) and groups (GID)
sudo id       # root's user ID (UID=0)
Command What it does
sudo <command> Run command as root
sudo -k Forget cached sudo password
whoami Show current user
id Show user ID and groups

Check Your Understanding

1. Who is root?

What is the root user in Linux?

Reveal Answer

The root user is the system administrator with user ID 0. It can do anything - no limits, no permission checks.

2. Why not log in as root?

Why do modern Linux systems lock the root account and use sudo instead?

Reveal Answer

One mistake as root can destroy the entire system. Using sudo limits damage to a single command.

3. What does sudo do?

You try to look inside /root but get "Permission denied".

What command do you type to view the contents of /root?

Reveal Answer

sudo ls /root

4. sudo timeout

You just used sudo. Now you want to make sure the next sudo asks for your password again.

What command do you type?

Reveal Answer

sudo -k (kills the cached password)

5. Root Location

Where does the root user's home directory live?

Reveal Answer

/root (not /home/root)