THE FQDN

You can’t change the FQDN
(as returned by hostname –fqdn) or
the DNS domain name (as returned by
dnsdomainname) with this command. The
FQDN of the system is the name that
the resolver(3) returns for the host
name.

Technically: The FQDN is the name
gethostbyname(2) returns for the host
name returned by gethostname(2). The
DNS domain name is the part after the
first dot.

Therefore it depends on the
configuration (usually in
/etc/host.conf) how you can change
it. Usually (if the hosts file is
parsed before DNS or NIS) you can
change it in /etc/hosts.

NOTES

The address families hostname tries when looking up the FQDN,
aliases
and network addresses of the host are determined by the
configuration
of your resolver. For instance,on GNU Libc systems,the
resolver can
be instructed to try IPv6 lookups first by using the inet6
option in /etc/resolv.conf.

FILES

/etc/hosts /etc/hostname This file should only contain domain name and not the full FQDN.