Currently, Gentoo's /etc/conf.d/net is used for setting the DNS domain name and the NIS domain name. This functionality should be integrated into /etc/init.d/hostname.

Suggested implementation:

hostname="ninja2" -> set hostname to "ninja2", no DNS domain name.
hostname="ninja2.funtoo.org" -> set hostname to "ninja2", DNS domain to "funtoo.org" (FQDN: ninja2.funtoo.org)

we may want to add nisdomainname= variable for setting the NIS domain name via the nisdomainname command.