Pod resolv.conf modification on the fly

start.sh

#!/bin/bash
set -ex

export DNS_TCP=${DNS_TCP:-false}

if [ "$DNS_TCP" == true ]; then
    # enable tcp DNS resloving
    if [ $(grep -w options /etc/resolv.conf | wc -l) -eq 0 ]
    then
        echo "options use-vc" >> /etc/resolv.conf
    else
        mapfile </etc/resolv.conf resolv && sed -r 's/(options.*)/\1 use-vc/g; s/^\s+//g' <<<"${resolv[*]}" > /etc/resolv.conf
    fi
fi