if [ ! -z $new_host_name ]; then
    hostname $new_host_name.${new_domain_name:-local}
    hostname >/etc/hostname
    sed -i "s/\([0-9]*\.[0-9]*\.[0-9]*\.[0-9]*\).*$old_host_name\.$old_domain_name.*/\1    $new_host_name.${new_domain_name:-local}     $new_host_name/" /etc/hosts
fi