How to flush the DNS cache on Ubuntu Server

What you’ll need

The only thing you’ll need to flush the DNS cache on your Ubuntu Server is a user with sudo privileges. With that user at the ready, let’s get to the flushing.

How to flush your DNS cache

Once upon a time, the DNS cache was flushed with a command like:

sudo systemd-resolve --flush-caches

The above command will still work on Ubuntu 20.04. But if you’ve upgraded to Jammy Jellyfish (22.04), the process has changed. This new command is backward compatible with 20.04

First, let’s view the statistics of our DNS cache with the command:

resolvectl statistics

You should see output similar to this:

Transactions
Current Transactions: 0

Total Transactions: 3520

Cache

Current Cache Size: 1

Cache Hits: 9

Cache Misses: 1388

DNSSEC Verdicts

Secure: 0

Insecure: 0

Bogus: 0

Indeterminate: 0

To flush the cache, issue the command:

resolvectl flush-caches

You should see the Cache Size entry reset to 0.

Believe it or not, that’s all there is to flush a DNS cache in Ubuntu. This works for both Ubuntu Server and Ubuntu Desktop. If you’ve gone down a network troubleshooting rabbit hole and nothing seems to work, you might try flushing the DNS cache and see if that doesn’t resolve your problem.