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Changing a user password in Linux is not just about executing a series of commands; it’s about ensuring the integrity and security of the system. With this guide, users will gain the confidence to perform this task efficiently and securely. Let’s dive into the process, where you’ll learn the steps to change a password, ensuring your Debian system remains secure.

Contents

  1. Changing User Password on Debian
    1. Opening the Terminal
    2. Gaining Root Access
    3. Change User Password
      1. Verifying Password Change
  2. Enforcing Password Update on Next Login
    1. Setting Password Expiry for Enhanced Security
    2. User Experience Post-Password Expiry
  3. Securely Disabling the Root Account
    1. Exiting the Root Account
    2. Locking the Root Account
    3. Confirming Root Account Disablement
  4. Modifying Group Passwords
    1. Changing a Group’s Password
    2. Removing a Group’s Password
    3. Restricting Group Access
  5. Best Practices for Changing User Passwords
    1. Selecting a Robust Password
    2. Avoiding Predictable Passwords
    3. Restricting Root Access Post-Changes
  6. Resources

Changing User Password on Debian

Opening the Terminal

Initiate the process by opening the terminal. For desktop environments, this involves clicking the terminal icon. In server environments, you’re typically already in a command-line interface. The terminal prompt appears once the terminal is open.

Gaining Root Access

Root or superuser privileges are required to change user passwords. Gain root access with this command and input your root password when prompted: 

su

Change User Password

As a root user, modify the user’s password using the following command: 

passwd username

Example output: 

Enter new UNIX password:
Retype new UNIX password:

In this command, replace “username” with the actual username. You’ll be prompted to enter and re-enter a new password. Ensure the new password is strong, combining upper and lower-case letters, numbers, and special characters.

Verifying Password Change

Upon successful password update, you should see: 

passwd: password updated successfully

To confirm the password change, log out and attempt to log in as the user with the new set password. Successful login indicates a successful password update.

Enforcing Password Update on Next Login

Setting Password Expiry for Enhanced Security

IMPORTANT NOTE: It's recommended organizations to not force regular password expiry.

Linux systems typically do not set password expiration by default. To enhance security, especially in environments requiring frequent password updates, use the passwd command with the --expire option. This command forces a user to update their password at their next login.

There is several case scenarios for this, like assigning a temporary password to a user for example, and force that user to change password on login.

The command syntax is as follows: 

sudo passwd --expire username

Replace ‘username’ with the actual username of the account. Upon execution, the system will display: 

passwd: password expiry information changed.

User Experience Post-Password Expiry

After setting the password to expire, the next time the user attempts to log in, they will encounter a message indicating that their password has expired.

Here is an example of what the user will see upon login: 

ssh username@192.168.0.1
 WARNING: Your password has expired.
 You must change your password now and login again!
 Changing password for username
 (current) UNIX password:
 Enter new UNIX password:
 Retype new UNIX password:
 passwd: password updated successfully
 Connection to 192.168.0.1 closed.
 Once the user sets a new password, the connection will be closed.

This prompt ensures the user enters a new password, following which the system will close the connection.

Securely Disabling the Root Account

Exiting the Root Account

Post making necessary changes as a root user in a Linux system, it’s critical to exit the root account to enhance security. To log out from the root account, enter this command in the terminal: 

exit

This command effectively logs you out from the root session, reverting you back to your standard user account.

On the default shell, if you see the symbol $, means you are logged in as a regular user and if you see the symbol #, you are effectively logged in as root.

WARNING 

Using root on Linux is generally discouraged because it grants unlimited system privileges, creating significant security risks. Any mistake or malicious program running as root has complete access to modify or damage your system. This bypasses important security protections and makes it difficult to track who made changes. It's much safer to use a regular user account and temporarily elevate privileges with [[sudo]] only when necessary for specific administrative tasks.

Locking the Root Account

Further securing the system involves locking the root account. This step is vital to prevent unauthorized root access. Execute the following command to lock the root account: 

sudo passwd -l root

This command disables the root account, making it inaccessible for login.

Confirming Root Account Disablement

To ensure the root account is indeed locked, attempt to log in as root. The system should display an error message confirming that the account is locked: 

Login incorrect or Account locked

This measure is a critical security practice in Linux administration, ensuring that the powerful root account remains secure and inaccessible for unauthorized use.

Modifying Group Passwords

Changing a Group’s Password

In Linux, updating a group’s password is made through the passwd command, combined with the -g option. This action is essential for maintaining group security and ensuring that all group members have the required access.

To change a group’s password, use this syntax: 

passwd -g groupname

Replace groupname with the actual name of the group. For instance, to modify the password for a group named testgroup, the command is: 

passwd -g testgroup

It’s important to note that this process doesn’t require the current group password. After executing the command, you’ll be prompted to enter the new password.

Removing a Group’s Password

To enhance accessibility within a group, the current password can be removed. This is done using the -r option along with -g, which eliminates the password requirement for group access: 

passwd -r -g groupname

Restricting Group Access

To restrict access to a specific group, the -R option is used with the -g option. This command ensures that only members of the specified group have access to its resources, barring all others: 

passwd -R -g groupname

This restriction is a key tool for administrators to control access to group resources in a Linux environment, ensuring that only authorized personnel have access.

Best Practices for Changing User Passwords

Selecting a Robust Password

When setting a new password on Debian, it’s crucial to choose one that’s strong and secure. A robust password includes a mix of upper and lower case letters, numbers, and special characters. This diversity makes the password more resistant to guessing and brute-force attacks.

Avoiding Predictable Passwords

It’s imperative to steer clear of passwords that are easy to guess. Common choices like “password,” “123456,” or simple patterns are vulnerable to security breaches. Opt for unique combinations that are not easily decipherable.

Restricting Root Access Post-Changes

After using the root account for system modifications, ensure to disable root access. This step is vital in safeguarding your Linux system against unauthorized access and potential security threats. On Debian this feature is not disabled by default, but it's good practice to effectively disable root when logging in using SSH.

Resources