From the collectd.conf documentation
Hostname Name
Sets the hostname that identifies a host. If you omit this setting, the
hostname will be
determinded using the gethostname(2) system call.
FQDNLookup true|false
If Hostname is determined automatically this setting controls whether or
not the daemon should
try to figure out the ``fully qualified domain name'', FQDN. This is
done using a lookup of the name
returned by gethostname.
Using this feature (i. e. setting this option to true) is recommended.
However, to preserve
backwards compatibility the default is set to false. The sample config file that
is installed with
makeinstall includes a line which sets this option, though, so that default
installations will have
this setting enabled.
I'll try modifying a config in my setup to omit the hostname but set the
FQDNLookup to true
-mark