Managing User Password Policies with the `lchage` Command (with examples)

The lchage command is a tool used in Linux systems to display or modify the password expiration policies for user accounts. This utility allows system administrators to ensure that users maintain their password security by enforcing various policies such as password expiry, mandatory password changes, and warning periods before password expiration. The command helps in maintaining a secure user authentication setup by controlling how and when user passwords should be updated.

Use Case 1: Disable Password Expiration for the User

Code:

sudo lchage --date -1 username

Motivation:

In certain environments, it might be necessary to disable password expiration for specific users, especially for service accounts or system accounts that are tightly integrated into automated workflows and scripts. Consistent password expiration for these users could potentially disrupt critical services or processes. Therefore, administrators may choose to disable password expiration temporarily or permanently for these accounts to avoid such disruptions.

Explanation:

• sudo: Executes the command with superuser privileges, which is necessary for modifying user password policies.
• lchage: The command invoked to manage password policies.
• --date -1: Uses the --date flag with a value of -1, which tells lchage to effectively disable password expiration by setting no expiration date.
• username: Specifies the user account for which the password expiration is being disabled.

Example Output:

While disabling password expiration might not provide a direct output confirmation, administrators can verify changes by using the lchage command to list the user’s password policy (covered in the next use case).

Use Case 2: Display the Password Policy for the User

Code:

sudo lchage --list username

Motivation:

Regular reviews of user password policies can be crucial for ensuring compliance with security policies and standards. By displaying the password policy for a user, an administrator can verify settings such as password age, maximum age, and warning period before expiration. It is an essential capability for auditing and understanding the current security posture regarding user accounts.

Explanation:

• sudo: Runs the command with the required administrative privileges.
• lchage: Calls the tool that manages password change policies.
• --list: A flag that instructs the tool to display a report of the current password policy settings for the specified user.
• username: Indicates the specific user account you want to retrieve the policy information for.

Example Output:

Last password change   : Jan 01, 2023
Password expires       : never
Password inactive      : never
Account expires        : never
Minimum number of days between password change        : 0
Maximum number of days between password change        : never
Number of days of warning before password expires     : 7

Use Case 3: Require Password Change for the User After a Certain Number of Days

Code:

sudo lchage --maxdays number_of_days username

Motivation:

To improve security, organizations often enforce regular password changes. By enforcing a maximum number of days a password can be used, you can ensure that users frequently update their passwords, thus reducing the risk of unauthorized access from compromised credentials that are guessed or broken over time.

Explanation:

• sudo: Used to execute the command with necessary administrative rights.
• lchage: The command for changing password policies.
• --maxdays: Specifies the maximum number of days a password can be valid before requiring a change.
• number_of_days: A placeholder indicating how many days the user can have the same password.
• username: The account for which you are setting this policy.

Example Output:

This change does not generate a visual output; the effectiveness of this change can be checked using the --list option previously described.

Use Case 4: Start Warning the User a Certain Number of Days Before the Password Expires

Code:

sudo lchage --warndays number_of_days username

Motivation:

Providing users with sufficient notice before their passwords expire is crucial to prevent sudden lockouts. Configuring a warning period gives users the lead time to prepare and change their passwords before they expire, ensuring uninterrupted access and usability.

Explanation:

• sudo: Executes the command with administrative permissions.
• lchage: The command at the heart of managing password policies.
• --warndays: Sets the number of days before password expiration that the system should begin issuing warnings to the user.
• number_of_days: Represents the warning period in days before the password’s expiry.
• username: Identifies which user account the warning policy is to be applied to.

Example Output:

Similar to other administrative changes, this does not produce a direct output, but its success can be verified with the --list option.

Conclusion

The lchage command provides a powerful set of tools for Linux system administrators to manage user password policies effectively. Whether disabling password expiration, setting expiration policies, or configuring warning periods, it offers various options to ensure a secure and well-maintained user authentication environment. By understanding these use cases, administrators can ensure that their systems are both user-friendly and secure.