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