I've found a solution using DNS Lookup - Online Tool | HackerTarget.com
Luckily the site has an API to which makes downloading a list of DNS records simple using something like curl. The API is designed to be used in an ad-hoc fashion not for bulk queries and is limited to 100 (total) requests from a single IP Address per day.
Quick word of warning, I'm using this script on a pfSense server that's using pfblocker for ad domain blocking. Whilst the script uses standard FreeBSD/Linux type commands, the paths to those commands maybe different when run on a pi-hole.
Enough preamble, here's the script:
echo "" > /root/youtube/youtube-domains.txt echo "" > /root/youtube/youtube-filtered.txt echo "" > /root/youtube/youtube-ads.txt /usr/local/bin/curl "https://api.hackertarget.com/hostsearch/?q=googlevideo.com" > /root/youtube/youtube-domains.txt cat /root/youtube/youtube-domains.txt | cut -d, -f1 > /root/youtube/youtube-filtered.txt /usr/bin/sed '1d' /root/youtube/youtube-filtered.txt > /root/youtube/youtube-ads.txt
Lines 1 - 3 clear down text files, as per previous scripts above
Line 4 downloads the DNS records from api.hackertarget.com in comma separated variables format: domain,IP address
Line 5 removes the second entry per line (the IP address)
Line 6 removes the top entry from the resulting file. This just has the text "googlevideo.com" in it
Done!
As I say, works for me under pfSense with pfblocker, so should work under pi-hole with minor modification