This weekend I came across several pages on the web suggesting ways to flush the DNS cache on Ubuntu. I will not point to the offending pages here but they are easy to find with Google. Most of them are wrong in several ways.

1. Ubuntu doesn’t install a DNS cache by default
2. Most of the pages say something along the lines of to flush the DNS cache you need to restart the nscd deamon.
3. See 1
4. As a result of 1 – They tell you to install nscd so that you can then restart nscd!
5. I redirect your attention to issue 1.

If you really want a local cache then I would suggest installing unbound which will work better and give you DNSSEC as well.