How can I flush the DNS cache on my Ready NAS?

Which NAS do you have?

Also, are you running a DNS server on the NAS? Not sure if there is anything cached if you aren't.

However, you can try /etc/init.d/networking restart

I have a ReadyNAS Duo v2. I never installed a DNS server, but this was the suggestion by a guy on the tracker forum.

Still no luck by the way. I can connect to another tracker fine, but I'm invisible on this certain one. Even though I'm seeding, the tracker doesn't see me seeding.

It seems unlikely that this is due to DNS caching.

Try using host to do a DNS lookup on the tracker (host trackername - no need for the udp:// or :port). If it succeeds, it will return the IP address associated with the tracker. You can then make sure that is the correct address. If the address is wrong, it could be caching, but it could also be blocked or redirected by your DNS server (usually your ISPs). If you have parental controls enabled in your router, that could also block/interfere with DNS.

Also, see if you can seed from another device on your home network.

I can seed just fine from my computer. It's just seeding to a specific tracker from this specific device that's causing problems.

Well, try using host on the NAS and see if it resolves to the correct IP [or not].

It ping the right IP and everything. I'm starting to wonder if the problem is on my side or not. I keep getting a "cannot connect to tracker" error. Other people connect just fine though.

And it's just on this one tracker too. Is there anywhere the NAS stores IP addresses like a hosts file or something?

if you enter go into ssh and type "hosts trackername"
does it give you the right IP address or not?????

IF yes, then it isn't a DNS cache, if not, there is a problem there to fix.