Why is DNS Resolution for my Domain Failing?

There are a few things you will want to check (there may be others):

[ ] Have you registered the domain with a registrar? Linode can host DNS records for your domain, but you will need to purchase your domain from a third party provider. You can search the internet for "Domain Registrar Reviews" to find one.

[ ] Is your domain currently active with your registrar?

An answer like this might involve additional investigation with your registrar.

whois example.com | grep "Status:"

Status: serverHold
Status: serverUpdateProhibited

[ ] Is your domain pointing to Linode's nameservers?:

whois example.com | grep "Name Server:"

Name Server: NS5.LINODE.COM
Name Server: NS1.LINODE.COM
Name Server: NS3.LINODE.COM
Name Server: NS2.LINODE.COM
Name Server: NS4.LINODE.COM

[ ] If you have recently made changes to your DNS records, have you waited the TTL + at least 15 minutes to ensure they are active and not cached?

[ ] Do you have any local resolvers configured for the system from which you are querying from that may be offering conflicting records?

[ ] Are there any overriding entries in your /etc/hosts file?

[ ] Can you perform the command dig @ns1.linode.com -tA example.com and get the answer you expect?

I hope this helps!