Subdomain, delayed setup (though it appeared to be setup)
I setup an A record for a subdomain about 20 minutes ago (it's about 2:00 AM EST), and I setup a vhost in apache. Apache didn't complain when I restarted it, and the Linode Manager showed the A record as being there. However, up to a few minutes ago, trying to visit subdomain.example.com showed a server not found error, while example.com and mail.example.com both work fine. It seems to be connecting fine now, I am just wandering why there was about a 20 minute delay.
So one possibility is that you just missed the prior update when you made your change you could see a full 15 minute latency between an edit and it being live in the Linode servers.
The other possibility is that the update occurred more quickly (since, on average it should only take about half the quarter hour update cycle) but that you tested before it happened and your local DNS resolver - either your own or your ISPs - cached the negative response. Then, even once the Linode servers had new information you had to wait for your local resolver's negative cache entry to time out.
When in doubt, you can always directly query (with a tool like nslookup or dig) the Linode nameservers (ns1-ns5.linode.com) to see what data they have.
It didn't mention anything about the 15 minute wait. I just added another subdomain, (…)
Not sure about a brand new domain addition, but I just brought up the editing screen for an existing domain and at the bottom it shows:
> NOTE: Changes made to a master zone will take effect in our nameservers every quarter hour.
so I think that's still the interval.