kubespray/roles/kubernetes/preinstall/templates/dhclient_dnsupdate.sh.j2

#!/bin/sh
#
# Prepend resolver options to /etc/resolv.conf after dhclient`
# regenerates the file. See man (5) resolver for more details.
#
if [ $reason = "BOUND" ]; then
  if [ -n "$new_domain_search" -o -n "$new_domain_name_servers" ]; then
    RESOLV_CONF=$(cat /etc/resolv.conf | sed -r '/^options (timeout|attempts|ndots).*$/d')
    OPTIONS="options timeout:2\noptions attempts:2\noptions ndots:{{ ndots }}"

    printf "%b\n" "$RESOLV_CONF\n$OPTIONS" > /etc/resolv.conf
  fi
fi