domainname - display or set the name of the current NIS domain for this
The domainname command, when used without an argument, displays the name of
the current domain. When used with argument, sets the current Network
Information Service (NIS) domain name to the specified domain name.
A domain is a logical grouping of networked-connected systems established
for the purpose of sharing a common set of NIS data files. Domains are only
used by NIS.
The NIS maps for a particular domain are stored in the directory
/var/yp/domainname on each NIS server. Each NIS map contains a set of
keys and associated key values. For example, in a map called hosts.byname,
the host names stored there constitute the keys. The corresponding internet
addresses of each host constitute the associated key values.