useradd and userdel in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the useradd command do in Linux?

The useradd command creates a new user account on the system. It sets up the user's home directory, default shell, and other settings.

beginner

What is the purpose of the userdel command?

The userdel command deletes a user account from the system. It can also remove the user's home directory and files if used with the right options.

intermediate

How do you create a user with a specific home directory using useradd?

Use useradd -d /path/to/home username. The -d option sets the home directory for the new user.

intermediate

What option with userdel removes the user's home directory and mail spool?

The -r option deletes the user's home directory and mail spool along with the user account: userdel -r username.

beginner

Why should you be careful when using userdel -r?

Because it permanently deletes the user's home directory and files. If important data is there, it will be lost. Always back up if needed.

Which command creates a new user account in Linux?

A useradd

B userdel

C usermod

D passwd

useradd is used to create new user accounts.

What does the -r option do with userdel?

A Resets the user password

B Removes the user account only

C Renames the user account

D Removes the user account and home directory

The -r option deletes the user account and the user's home directory.

How do you specify a custom home directory when adding a user?

A useradd -h /home/custom user

B useradd -d /home/custom user

C useradd -m /home/custom user

D useradd --home /home/custom user

The -d option sets the home directory path.

Which command deletes a user account but keeps the home directory?

A userdel username

B userdel -r username

C useradd username

D usermod -d username

userdel username deletes the user but leaves the home directory intact.

What should you do before running userdel -r?

A Nothing, it is safe always

B Change the user's password

C Back up important user files

D Restart the system

Backing up files prevents data loss since -r deletes user files.

Explain how to add a new user with a custom home directory and then delete that user including their files.

Think about the options that control home directory and file removal.

Describe the risks of using userdel -r and how to avoid them.

Consider what happens to user data when deleting accounts.

Practice

1. What does the useradd command do in Linux?

easy

A. Lists all users on the system

B. Deletes an existing user account

C. Changes the password of a user

D. Creates a new user account

Solution

1. Step 1: Understand the purpose of useradd

   The useradd command is used to create new user accounts on a Linux system.

2. Step 2: Differentiate from other commands

   userdel deletes users, passwd changes passwords, and listing users is done by other commands like cat /etc/passwd.

3. Final Answer:

   Creates a new user account -> Option D

4. Quick Check:

   useradd = create user [OK]

Hint: Remember: add means create, del means delete [OK]

Common Mistakes:

• Confusing useradd with userdel
• Thinking useradd lists users
• Mixing useradd with password commands

2. Which of the following is the correct syntax to create a user with a home directory?

easy

A. useradd -r username

B. useradd username

C. useradd -m username

D. userdel -m username

Solution

1. Step 1: Identify the option for creating home directory

   The -m option with useradd creates the user's home directory.

2. Step 2: Check other options

   -r is for system users or removing files with userdel, so it is incorrect here.

3. Final Answer:

   useradd -m username -> Option C

4. Quick Check:

   -m means make home directory [OK]

Hint: Use -m with useradd to create home folder [OK]

Common Mistakes:

• Using userdel instead of useradd
• Forgetting the -m option for home directory
• Using -r option with useradd

3. What will be the result of this command sequence?

useradd -m alice
userdel alice

medium

A. User alice is deleted but home directory remains

B. User alice and home directory are deleted

C. User alice is created but deletion fails

D. Syntax error occurs

Solution

1. Step 1: Create user alice with home directory

   useradd -m alice creates user alice and a home folder.

2. Step 2: Delete user alice without -r option

   userdel alice deletes the user but does not remove the home directory unless -r is used.

3. Final Answer:

   User alice is deleted but home directory remains -> Option A

4. Quick Check:

   userdel without -r keeps files [OK]

Hint: userdel needs -r to remove home directory [OK]

Common Mistakes:

• Assuming home directory is deleted without -r
• Thinking userdel fails without -r
• Confusing useradd options with userdel

4. You run userdel -r bob but get an error saying user bob does not exist. What is the likely cause?

medium

A. The home directory is missing

B. User bob was never created

C. You need to use useradd to delete users

D. The -r option is invalid with userdel

Solution

1. Step 1: Understand the error message

   The error says user bob does not exist, so the system cannot delete a non-existent user.

2. Step 2: Check command validity

   userdel -r bob is valid syntax to delete user and home directory, so the error is not due to syntax.

3. Final Answer:

   User bob was never created -> Option B

4. Quick Check:

   User must exist before deletion [OK]

Hint: Check if user exists before deleting [OK]

Common Mistakes:

• Thinking -r is invalid option
• Trying to delete users with useradd
• Assuming home directory missing causes error

5. You want to create a script that adds a user with a home directory and then deletes the user along with all their files. Which commands should you use in order?

hard

A. useradd -m username; userdel -r username

B. useradd username; userdel username

C. userdel -r username; useradd -m username

D. userdel username; useradd username

Solution

1. Step 1: Add user with home directory

   Use useradd -m username to create the user and their home folder.

2. Step 2: Delete user and all files

   Use userdel -r username to remove the user and their home directory and files.

3. Final Answer:

   useradd -m username; userdel -r username -> Option A

4. Quick Check:

   Add with -m, delete with -r for files [OK]

Hint: Add with -m, delete with -r to remove files [OK]

Common Mistakes:

• Deleting before adding user
• Forgetting -m when adding user
• Forgetting -r when deleting user