I spent a couple hours today fighting with Linux update clients for OpenDNS and DNS-o-matic (dnsomatic.com). I tried three update clients: inadyn, ddclient, and finally update-dnsomatic.
I couldn’t figure out why I kept getting authentication errors like “401 Unauthorized” and “skipping update” and “badauth” from either OpenDNS or DNS-o-matic.
As it turns out, when the update client asks for your username, what it really wants is your email address. And when it asks for your password, it wants you to have a relatively simple (numbers and letters only) password, not one with any special characters.
After changing my password to a simpler one, and using my email address to login, I was set.
As an aside, if you’re new to this, the easiest client to handle, in my opinion, is update-dnsomatic.
And I only stumbled upon this, but if you use both DynDNS and OpenDNS, the simplest way to update both is to use DNS-o-Matic (with the update-dnsomatic client). It’s a service put out by OpenDNS that will detect changes to your IP and make changes to several services for you — so all you need is one update client (and configuration) on your end rather than several.