nss-mdns is a plug-in for the GNU Name Service Switch (NSS)
functionality of the GNU C Library (glibc) providing a hostname
resolution via Multicast DNS (aka Zeroconf, aka Apple Rendezvous, aka
Apple Bonjour), and effectively allowing name resolution by common
Unix/Linux programs in the ad-hoc mDNS domain .local.

nss-mdns provides only client functionality, which means that you have
to run a mDNS responder daemon separately from nss-mdns if you want to
register the local hostname via mDNS. I recommend Avahi.

By default, nss-mdns tries to contact a running avahi-daemon to resolve
hostnames and addresses and makes use of its superior record cacheing.