The /usr/bin/getent command will display a list of entries, Get Entries. The entries are resolved by Name Service Switch Libraries, which are configured in the /etc/nsswitch.conf file. This file has a list of databases and libraries that will be used to access those databases.

For example, we could use the getent passwd command to display all users, or getent group to display all groups. We could extend this though to commands such as getent hosts to display host file entries and getent aliases to display user aliases on the system.

The nsswitch.conf file will define the libraries used to access the passwd database. On a standard CentOS system, /etc/passwd is often the only local file, but an enterprise system could include Lightweight Directory Access Protocol (LDAP) modules. In the next chapter, we will learn more using directory services.

We search the /etc/nsswitch file for the passwd database using grep:

# grep passwd /etc/nsswitch.conf

We can see that on my system, we just use...