jbo5112 wrote:If OpenDNS is used as a fallback, I'm pretty sure it affects every DNS lookup that isn't found on the normal server.
That is how OpenDNS works, correct. But again, OpenDNS is only used when the default DNS is not working properly on your Linux Mint installation.
My default DNS is working properly on my Linux Mint installation, so going to your example page http://invalid.opendns.redirect.pastebay.net/
returns as expected Firefox's "Unable to connect" error. OpenDNS is not used if it is not needed.
jbo5112 wrote:I have a caching DNS server on my computer
You do not; dnsmasq is running in non-caching mode and is included as a way to improve DNS resolution handling when using VPNs (like for example for people connecting from remote location to their corporate network). If you look up your dnsmasq process with ps you can see with what parameters it was started. It is started by NetworkManager. Here is how NetworkManager invokes it on Linux Mint 14:
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/usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces --pid-file=/var/run/sendsigs.omit.d/network-manager.dnsmasq.pid --listen-address=127.0.1.1 --conf-file=/var/run/nm-dns-dnsmasq.conf --cache-size=0 --proxy-dnssec --enable-dbus=org.freedesktop.NetworkManager.dnsmasq --conf-dir=/etc/NetworkManager/dnsmasq.d
From the manpage you can see that --cache-size=0 means it is indeed running in non-caching mode (as caching could possibly be exploited):
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Set the size of dnsmasq's cache. The default is 150 names. Setting the cache size to zero disables caching.
jbo5112 wrote:If I disable OpenDNS and clear my DNS cache, I get the proper DNS lookup failed page.
This is curious, and I'm not sure what could be causing your default DNS to fail initially (triggering the fallback to OpenDNS).
jbo5112 wrote:I don't know their business model
OpenDNS has several commercial services targeted at businesses. Their free services are supported by ads you get to see when you go to non-existent domain. There are various ways to disable that redirection if you so desire.
I understand some of your concerns, though have hopefully laid to rest some above. You are not the first to voice your concern/distrust of OpenDNS. Should Linux Mint instead use Google's DNS as a fallback DNS, there would be other users (if not some of the same) that would voice their concern/distrust of that. There's no pleasing everybody...
The intent of the Linux Mint developers is for those users for which their default DNS isn't working properly on Linux Mint, to not be without a DNS and so to be able to continue to use Internet (and perhaps do a search and figure out how to fix that issue). A common cause is running Linux Mint on a virtual machine with a misconfigured virtual network.