How to Flush the DNS Cache on BlueQuartz

09:59.15 - Tuesday 4th September 2007   (Link to This Entry)

Imagine you've just added a new domain to your BlueQuartz server. It was previously on another IP address and you've added the relevent DNS entries on your box, changed your nameservers and the new site shows up in your browser - great, all as expected.

But then you check email delivery and find that, while email from outside the server is being delivered, anything generated on the server, or send via that server's SMTP, is being sent off to the old IP address. The problem you have is that your server is caching the old DNS entries until they expire.

In Linux, DNS Caching is handled by the nscd process. To restart this process, and thus flus the DNS cache, you'll need to type one of the following while logged in as root:

/etc/rc.d/init.d/nscd restart    (for general Linux, or... )
/etc/init.d/nscd restart         (for BlueQuartz)

You may find that this doesn't work, in which case, try using 'stop' instead of restart, ping your domain name from the server, then use 'start' to restart the service. Your updated IP address should now show up.