Isp error

[Alex1]

root@alex-desktop:/var/www/ispcp/engine/setup# perl ispcp-setup


Welcome to ispCP '1.0.0 RC6 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 !
root@alex-desktop:/var/www/ispcp/engine/setup#

why?