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I am trying to get all the A records for some domains. The best way I have found is to use https://www.whatsmydns.net and the nexcess tool. The issue is that it is very slow to copy paste them and sort through all the trash. I tried some scraping but the javascript means it breaks half the time.

Another idea was to just run the dns queries from my server but I am unsure how effective that would be since most dns servers are anycast.

Is it possible to write a script that did "nslookup google.com 8.8.8.8" and kept going through a list of dns servers then outputted just the IP addresses from the A records to a file named google.com.txt or something and removed any duplicates.

Thanks in advance!

  • 1
    are you comfortable missing some round-robin A records? It sounds like you're wanting a zone transfer ("get all the A records for some domains"), which has been locked down for ... some time now. – Jeff Schaller Aug 24 '15 at 17:04
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The dig(1) or host(1) commands can be automated to lookup A records:

% for d in example.com example.org; do dig +short A $d; done 
93.184.216.34
93.184.216.34
% for d in example.com example.org; do host -t A $d; done                   
example.com has address 93.184.216.34
example.org has address 93.184.216.34
%

As a script, one way would be:

$ cat domlu
#!/bin/sh
# accepts list of domains one per line on standard input, emits unique
# A records for said domains (assuming no errors, etc).
( while read domain; do
  dig +short A "$domain"
done ) | sort -u
$ cat hl
example.com
example.org
$ chmod +x domlu 
$ ./domlu < hl
93.184.216.34
$ 
  • How can I make it iterate through a list of dns servers I create? This is exactly what I was looking for thx! – user130040 Aug 24 '15 at 17:23
  • Put the command above into a script. Then source another file with your list of servers set as a variable. So your script would start with something like: . ./servers.list for d in $servers; do ... Then in the servers.list file put in something like: servers="example.com example.org" (hmm...doesn't look like comments support block formatting. Someone may have to help me clarify this, or just add it to the answer.) – Rick Chatham Aug 24 '15 at 18:17

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