Command-Line Techniques for Listing Linux Users

Linux offers powerful command-line tools for system administrators to view and manage user accounts. Knowing how to list users efficiently helps you audit your system, monitor access, and ensure proper security configurations.

Listing Users from the /etc/passwd File

All user information is stored in the /etc/passwd file. You can display the file content using:

cat /etc/passwd

cat /etc/passwd

Each line represents a single user account, containing details like username, UID, GID, home directory, and shell. To extract only usernames, use:

cut -d: -f1 /etc/passwd

cut -d: -f1 /etc/passwd

This provides a simple list of all users on the system.

Using the getent Command

The getent command retrieves entries from administrative databases such as passwd or group. It’s more reliable for systems that use centralized authentication like LDAP.

getent passwd

getent passwd

To show just usernames:

getent passwd | cut -d: -f1

getent passwd | cut -d: -f1

This lists both local and network-based users if the system integrates with directory services.

The compgen Command

For a quick overview, compgen is a convenient command:

compgen -u

compgen -u

This outputs all usernames registered on the system. Similarly, to view all groups:

compgen -g

compgen -g

Checking Currently Logged-In Users

To find which users are actively logged in, use:

who

who

or

w

w

These commands show user sessions, terminal activity, and login times.

Combining Commands

You can combine commands for better insights. For example, to count total users:

getent passwd | wc -l

getent passwd | wc -l

This helps administrators track the number of registered accounts.

Conclusion

Mastering command-line techniques for listing users is essential for Linux administrators. Whether using /etc/passwd, getent, or compgen, these commands simplify user auditing and enhance security monitoring.