Hostname Error

[slayer]

Always i try to install ispcpi got errors while im set up front end

****:/var/www/ispcp/engine/setup# perl ispcp-setup
Generating database keys, it may take some time, please wait...
If it takes to long, please check http://www.isp-control.net/documentation...setup_mean


Welcome to ispCP '1.0.0 OMEGA' Setup Dialog.
This program will set up ispCP OMEGA system on your server.

Next you are asked to enter a "fully qualified hostname" (FQHN).
For more infos read http://en.wikipedia.org/wiki/FQDN.

hostname: Unknown host
ERROR: External command '/bin/hostname -f 1>/tmp/ispcp-setup.hostname' returned '1' status !

I cant write anithing after i type the command perl ispcp-setup ... error

pls help T_T