You’re about to move an application (or an entire data center!) to a new environment and you want to see what fully qualified domain names (FQDNs) you may have lingering around in your server’s hosts files.

Smart move. Failing to do this is often the cause of heartache in migration scenarios.

Usually, this would be a pretty painful and manual task of logging on to each server, searching through /etc/hosts and noting down the impacts in some spreadsheet. Thankfully you can now use our ‘hosts’ tool to help you quickly make sense of it all, effortlessly digging through each line and even aggregating all your hosts files by unique FQDN to keep it simple:

dns-tools hosts --dir hostfiles/ -r

Now, imagine that you have an application hosted on a server with an IP of ‘’ that you are planning on moving to the cloud. You want to quickly find out if you have any hardcoded references to this IP in any of your system’s hosts files that will need to be updated when you migrate. Our ‘hosts’ tool’s filter function can quickly narrow down which severs hosts file contain that IP:

dns-tools hosts --dir hostfiles --ip

You now have a list of all the hosts files that you need to remediate during your migration. Eiter update them in flight, or better yet: use DNS. :-)

Get dns-tools today!