Do you hate it when your ISP has old cached records because of a high TTL on the DNS record of the relevant domain? In plain English this means you often can't connect to a site or service because your ISP's DNS servers haven't gotten word of the new IP address (probably because they haven't checked). There are also some that are notorious for ignoring TTL and not updating records for days!
But if you are lucky and smart enough to have your own Linux based DNS server you can do the following:
rndc dumpdb -cache
This let's you see the cached entries by writing the bind cache to /var/named/data/cache_dump.db
If you just want to clear your DNS cache:
The above flushes all of your DNS cache which is never a bad idea since it saves memory and increases the performance potentially.
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