don't deliver gPXE to systems which allready have that user class option
[pxelator] / bin /
drwxr-xr-x   ..
-rwxr-xr-x 2362 dhcpd.pl
-rwxr-xr-x 61 install-debian.sh
-rwxr-xr-x 80 install-http.sh
-rwxr-xr-x 333 install-iso.sh
-rwxr-xr-x 70 network-config.sh
-rwxr-xr-x 1732 tftpd.pl