Re: [gentoo-user] Re: DNS server packages

[Alan McKinnon]

On 12/10/2015 19:43, James wrote:
> Alan McKinnon <alan.mckinnon <at> gmail.com> writes:
>
>
>>> I need to setup DNS primary/secondary systems on gentoo. So right now
>>> I'm looking for a suggested list of packages to install with Bind,
>>> iptables and DNSSEC-tools as these (2) gentoo dns servers will only
>>> run the minimum packages to operate securely?
>> auth or cache?
>
> These are the (2) net facing primary and slave dns servers, just for the
> few domain names I willauthenticate. They'll be behind a firewall
> (iptables/dmz) with no internal zone information.  Strictly auth, public
> facing, with DNSsec. The plan is to go slow with manual configuration and
> and slow add features like a database, as I roll out new auth-DNS servers
> on newer, embedded hardware (very small very low power, but lots of ram
> (2G)). So over time the scope will evolve. It's a manual approach to a
> refresher for me.  Eventually one of the auth-dns-slaves will be an arm
> cluster for performance testing on mesos. (That's a ways off).
>
>
> So also, the iptables rules for such a setup will need to be revisited,
> dusting off what I use to use. Again, the importance is trying different
> packages and sniffing the results and examining log files (manually and with
> scripts) on a log host. So only ports 53 (public/routable net visible
> and port 22 from a select sets of private ips is all these will need.

Then you need your chosen name server (bind), your chosen fw ruleset
generators (iptables, maybe some other front end) and maybe fail2ban or
one of it's friends if you find some port gets hammered.

Block all ports except 53 and 22, send all logs to a remote syslogger
and trawl through them to your heart's content. All very usual and normal.


>> First of all, bind is a pain to use. Reason: it's actually a reference
>> implementation that as usual got forced into production use. It's slower
>> than it could be because it deals with every possible corner case per RFC.
>> As an auth server (few queries) it's OK
>
> Bind is an old acquaintance of mine:: been a few years, hence the post.
> I may test/migrate to something else, later.

OK. For a few domains there's no benefit to using something other than
what you already know.

>
>> As a cache (many queries), there are better servers out there. I prefer
>> unbound.
>
> A Caching DNS server for internal usages is another project for another
> time. It will be totally isolated; still, good to know.
>
>
>>> Also, what is the (nominal) minimum amount of RAM needed to keep all
>>> routes in ram in these  name servers?
>> I don't understand. DNS servers don't keep routes in memory - routers do
>> that. Perhaps you mean cached DNS records?
>> DNS is light on RAM, there are only so many records typical users will
>> look up. DNS caches not too long ago ran for years problem free with a
>> puny few hundred MB. It's not something to be worried about.
>
> There should be a way to keep all the responses for the zones info they
> server in ram?  I know it often happens without intervention, but surely
> there are published methods to insure this info is kept "in ram" like bcachefs?
>
> Also flushing and ram usage status monitoring, as these auth dns servers
> will eventually migrate to low power embedded machines where keeping
> things in ram is critical to performance.

I can't help but feel you are worried about a problem that doesn't
exist. It takes lots and lots and lots of zones to get above 1M disk
space. How much ram do you think you need?

DNS caches are resource intensive (the upper limit on what they cache is
the internet)
DNS auth servers are not (their upper limit is how many bytes in the
zones) and they tend to idle most of the time. Well unless you do silly
things like set all TTLs to 1 (or god forbid, 0) and your auth server
becomes a cache

>
> 'eix -cC net-dns | grep auth'   <shows::    knot and nsd
>
> Curiously, Are they better, more easily secured solutions?
>
>
> It's been a hwile for me.... so a vetting of the packages is the first step
> for this minimal, manual setup of the auth-dns servers for a few domain names::
>
>
> Bind9, dnssec-tools, iptables:: any other packages relevant/germane
> on a amd-default profile [1] ?

Yes, that's about it.
Add in all the other usual server stuff you like to use - monitoring,
logging, notifications, mail, whatever


-- 
Alan McKinnon
alan.mckinnon@×××××.com