User access auditing is a critical aspect of maintaining a secure and efficient computing environment. It provides a detailed record of user activities, helping administrators identify potential security risks, ensure compliance with access control policies, and detect any unauthorized or suspicious activities. Regular user access audits can also aid in troubleshooting, system optimization, and forensic investigations. In essence, user access auditing is not just about security, but also about gaining insights into user behavior and system usage, which are invaluable for improving system reliability and performance.

1. Understand the Basics of Linux Permissions: Linux permissions are the first line of defense in securing your system. They determine who can read, write, and execute files. The three types of Linux permissions are User (u), Group (g), and Others (o). Familiarize yourself with the `chmod` command to modify these permissions and the `ls -l` command to view them.

2. Use the `last` Command: The `last` command in Linux provides a list of the last logged-in users on your system. This is a great tool for auditing user access as it allows you to see who has been accessing your system and when. Regularly check this log to keep track of user activity.

3. Audit User Accounts with `cat /etc/passwd`: This command will display a list of all user accounts on your Linux system. Regularly auditing this list can help you identify any unauthorized or inactive accounts that should be removed or disabled to enhance system security.

4. Monitor User Activity with `w` and `who` Commands: The `w` command displays who is currently logged in and what they are doing, while the `who` command shows who is currently logged in. Regularly monitoring user activity can help you identify any suspicious behavior.

5. Leverage Linux Auditing System (Auditd): Auditd is a powerful tool that allows you to monitor almost any event on your Linux system. You can use it to track security-related events, record system calls, and log any changes to your system files. Regularly review the logs generated by Auditd to ensure there are no unauthorized changes or activities on your system.

Regular monitoring and auditing of user activities are crucial to maintaining a secure Linux environment.

*This article was written with the help of AI tools and Grammarly.