Aca te mando una explicacion

Usage: hostname [-v] {hostname|-F file} set host name (from file)
domainname [-v] {nisdomain|-F file} set NIS domain name (from file)
hostname [-v] [-d|-f|-s|-a|-i|-y] display formated name
hostname [-v] display host name

hostname -V|--version|-h|--help print info and exit

dnsdomainname=hostname -d, {yp,nis,}domainname=hostname -y

-s, --short short host name
-a, --alias alias names
-i, --ip-address addresses for the host name
-f, --fqdn, --long long host name (FQDN)
-d, --domain DNS domain name
-y, --yp, --nis NIS/YP domain name
-F, --file read host name or NIS domain name from given file

This command can get or set the host name or the NIS domain name. You can
also get the DNS domain or the FQDN (fully qualified domain name).
Unless you are using bind or NIS for host lookups you can change the
FQDN (Fully Qualified Domain Name) and the DNS domain name (which is
part of the FQDN) in the /etc/hosts file.

Gracias por la explicacion.