This file should contain one entry, the fully qualified domain name of the administrative domain to which the local host's network belongs. You can supply this name to the Solaris installation program or edit the file at a later date.
In Figure 4–1, the networks are part of the domain deserts.worldwide, which was classified as a .com domain. Therefore, /etc/defaultdomain should contain the entry deserts.worldwide.com. For more information on network domains, refer to System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).