passwd (change password) in Linux CLI - Commands & Configuration

Introduction

Sometimes you need to change your login password on a Linux system to keep your account secure or update it after it expires. The passwd command lets you do this easily from the command line.

When you want to update your own user password for security reasons.

When an administrator needs to reset another user's password.

When a password has expired and you are prompted to change it at login.

When setting a new password after creating a user account.

When you suspect your password has been compromised and want to change it immediately.

Commands

This command lets the current user change their own password. It will prompt you to enter your current password first, then ask for the new password twice to confirm.

Terminal

passwd

Expected Output

Changing password for user yourusername.

Current password:

New password:

Retype new password:

passwd: password updated successfully

As an administrator, this command changes the password for user 'alice' without needing her current password. It will prompt for the new password twice.

Terminal

sudo passwd alice

Expected Output

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully

→

sudo - Run the command with administrator privileges to change another user's password.

Key Concept

If you remember nothing else, remember: passwd securely updates user passwords by prompting for the current password (unless run as admin) and confirming the new password twice.

Common Mistakes

Typing the new password only once without confirmation.

The passwd command requires you to enter the new password twice to avoid typos and ensure accuracy.

Always enter the new password twice exactly as prompted.

Trying to change another user's password without sudo or root privileges.

Without proper permissions, passwd will not allow changing other users' passwords.

Use sudo before passwd to gain the necessary permissions.

Entering the wrong current password when changing your own password.

The command will reject the change if the current password is incorrect.

Make sure to enter your current password correctly before setting a new one.

Summary

Use 'passwd' to change your own password securely by entering your current password and confirming the new one.

Administrators can change other users' passwords using 'sudo passwd username' without needing the current password.

Always enter the new password twice to confirm and avoid mistakes.

Practice

1. What does the passwd command do in Linux?

easy

A. It changes the password of a user securely.

B. It lists all users on the system.

C. It creates a new user account.

D. It deletes a user account.

Solution

1. Step 1: Understand the purpose of passwd

   The passwd command is designed to change user passwords securely on Linux systems.

2. Step 2: Compare options with command function

   Options B, C, and D relate to user management but not password changes. Only It changes the password of a user securely. correctly describes passwd.

3. Final Answer:

   It changes the password of a user securely. -> Option A

4. Quick Check:

   passwd changes passwords = A [OK]

Hint: Remember: passwd is for changing passwords only [OK]

Common Mistakes:

• Confusing passwd with user creation commands
• Thinking passwd lists users
• Assuming passwd deletes accounts

2. Which of the following is the correct syntax to change the password for user alice as root?

easy

A. passwd -p alice

B. passwd -u alice

C. passwd --change alice

D. passwd alice

Solution

1. Step 1: Recall root usage of passwd

   Root can change any user's password by running passwd username.

2. Step 2: Analyze options for correct syntax

   Only passwd alice uses the correct syntax. Options A, B, and C use invalid or non-existent flags.

3. Final Answer:

   passwd alice -> Option D

4. Quick Check:

   Root changes user password with passwd username = D [OK]

Hint: Use passwd username as root to change others' passwords [OK]

Common Mistakes:

• Adding wrong flags like -u or -p
• Using --change which is not a valid option
• Trying to change password without specifying username as root

3. What will happen if a normal user runs the command passwd root?

medium

A. The root password will be changed immediately.

B. The user will be prompted to enter the current root password.

C. The command will fail with a permission error.

D. The user's own password will be changed instead.

Solution

1. Step 1: Understand user permissions for passwd

   Only root can change other users' passwords. Normal users cannot change root's password.

2. Step 2: Predict command behavior for normal user

   When a normal user tries passwd root, the system denies permission and shows an error.

3. Final Answer:

   The command will fail with a permission error. -> Option C

4. Quick Check:

   Normal user cannot change root password = A [OK]

Hint: Only root can change other users' passwords; others get permission error [OK]

Common Mistakes:

• Assuming normal user can change root password
• Thinking user will be asked root's current password
• Believing user's own password changes instead

4. You run passwd alice as root but get the error: passwd: Authentication token manipulation error. What is the most likely cause?

medium

A. The password entered does not meet complexity rules.

B. You forgot to run the command with sudo or as root.

C. The user alice does not exist.

D. The passwd command is not installed.

Solution

1. Step 1: Understand the error meaning

   The error usually means insufficient permissions to update password files.

2. Step 2: Identify cause based on command context

   If not run as root or with sudo, passwd cannot change another user's password, causing this error.

3. Final Answer:

   You forgot to run the command with sudo or as root. -> Option B

4. Quick Check:

   Permission error means missing root privileges = C [OK]

Hint: Run passwd with root or sudo to avoid permission errors [OK]

Common Mistakes:

• Assuming user does not exist without checking
• Thinking password complexity causes this error
• Believing passwd is missing from system

5. You want to automate changing passwords for multiple users listed in a file users.txt. Which script snippet correctly changes each user's password to NewPass123 using passwd?

hard

A. for user in $(cat users.txt); do echo -e "NewPass123\nNewPass123" | passwd $user; done

B. while read user; do echo "NewPass123" | passwd --stdin $user; done < users.txt

C. for user in users.txt; do passwd $user NewPass123; done

D. cat users.txt | passwd -p NewPass123

Solution

1. Step 1: Understand how to feed password to passwd

   The passwd command reads password from standard input when piped, requiring password twice (new and confirmation).

2. Step 2: Analyze each script snippet

   while read user; do echo "NewPass123" | passwd --stdin $user; done < users.txt uses --stdin which is not standard on all systems. for user in $(cat users.txt); do echo -e "NewPass123\nNewPass123" | passwd $user; done correctly uses echo -e to send password twice piped to passwd. for user in users.txt; do passwd $user NewPass123; done incorrectly treats file name as user list. cat users.txt | passwd -p NewPass123 misuses passwd with pipe and -p which is invalid.

3. Final Answer:

   for user in $(cat users.txt); do echo -e "NewPass123\nNewPass123" | passwd $user; done -> Option A

4. Quick Check:

   Pipe password twice to passwd in loop = B [OK]

Hint: Pipe password twice with echo -e inside loop to automate [OK]

Common Mistakes:

• Using non-standard --stdin option
• Not sending password twice for confirmation
• Treating filename as username list without reading
• Misusing passwd options