nscd and DNS cache

[Ed Greshko]

On 05/18/2012 01:19 PM, JD wrote:
>
>
> On Thu, May 17, 2012 at 9:46 PM, Gordon Messmer <yinyang at eburg.com
> <mailto:yinyang at eburg.com>> wrote:
>
>     On 05/17/2012 09:19 PM, JD wrote:
>
>         That's excellent info. contradicts what other people have replied.
>
>
>     I also meant to point out that if you select nscd rather than a local caching
>     server, you don't need 127.0.0.1 in resolv.conf.  glibc connects to nscd via a
>     Unix socket rather than via IP.  The same is true of sssd on newer releases of
>     Fedora.  (nscd is, I believe, deprecated by Fedora in favor of sssd).
>     -- 
>
>
> I have switched to dnsmasq and so far, it is not too bad.
> Albeit, it's cache purge algorithm seems to have a very
> short ttl for any translation - like about 3 to 5 minutes!!!
> I looked for a  configuration in dnsmasq.conf that would
> force dnsmasq to keep a translation for a longer time in
> it's tables. I have not found it, or I must be going blind :)
>

There should not be a configuration for that.  If there is, then dnsmasq would be
going against the recommendations of the DNS RFCs.

The response to a DNS request includes a TTL (Time To Live).  According to the RFC....

TTL          which is the time to live of the RR.  This field is a 32
                bit integer in units of seconds, an is primarily used by
                resolvers when they cache RRs.  The TTL describes how
                long a RR can be cached before it should be discarded.


So, dnsmasq is dropping the records from its cache according to when the owner of the
record wants it.  This is how the DNS system is supposed to work.

-- 
Never be afraid to laugh at yourself, after all, you could be missing out on the joke
of the century. -- Dame Edna Everage