On Linux, as a system administrator, you often want to have a complete list of all the users and all the groups on your host.
It is quite crucial for security purposes to make sure that you have the correct amount of users and that you didn’t forget to delete some.
There are several ways to list users and groups on Linux.
First, you can read the passwd and the group file on your system, with cut commands to extract useful information.
A more effective way is to use the getent command that relies on the Name Service Switch, a Unix-based facility to define custom databases on your host.