How to clear DNS cache in 18.04

Solution 1:

This should clear it

# sudo systemd-resolve --flush-cache

You can check with

# sudo systemd-resolve --statistics

• it should show 0 in Current cache size

  DNSSEC supported by current servers: no
  Transactions
  Current Transactions: 0
  Total Transactions: 93750
  
  Cache
    Current Cache Size: 0
    Cache Hits: 18686
  Cache Misses: 28576
  
  DNSSEC Verdicts
        Secure: 0
      Insecure: 0
         Bogus: 0
  Indeterminate: 0
  

Solution 2:

Maybe this version also has two (2) DNS caches, like Ubuntu 20.10.

Please check the full tutorial to flush DNS caches:

https://askubuntu.com/a/1315569/136919