Without an argument, domainname displays the name
of the current domain, which typically encompasses a group of hosts or passwd entries under the same administration.The domainname command is used by various components of Solaris to
resolve names for types such as passwd, hosts and aliases. By default, various naming services
such as NIS, NIS+, the Internet Domain Name Service (DNS) and sendmail(1M)
use this domainname to resolve names. The domainname is normally a valid Internet domain name.
The domainname for various naming services can
also be set by other means. For example, ypinit can
be used to specify a different domain for all NIS calls. The file /etc/resolv.conf can be used
to specify a different domain for DNS lookups.
For sendmail, the domainname can be
specified through the sendmail_vars entry in
the /etc/nsswitch.conf file, or through the /etc/mail/sendmail.cf file. Only the superuser can set the name
of the domain by specifying the new domainname as an
argument. The domain name of the machine is usually set during boot-time
through the domainname command in the /etc/init.d/inetinit file. If the new domain name is not saved in the /etc/defaultdomain file, the machine will revert back to the old domain after rebooting.