bug#22209: name resolution failures in installer image

[ludo@gnu.org (Ludovic Courtès)]

Ricardo Wurmus <rekado@elephly.net> skribis:

> Leo Famulari <leo@famulari.name> writes:
>
>> On Sat, Dec 19, 2015 at 09:04:41AM +0100, Florian Paul Schmidt wrote:
>>> After booting the installer image, doing the ifconfig/dhclient dance,
>>> preparing the target fs, mounting it and starting the guix system init
>>> invocation at some point in time, though not predictably so, but
>>> usually after a couple of minutes (about 10 or so) name resolution
>>> will start to fail causing guix system init to fail.
>>
>> A little more information:
>>
>> I was installing on i686 bare metal from the current USB installation
>> image.
>>
>> I installed vim in the installation environment, and then when I
>> tried to run `guix system init...` I couldn't resolve hydra.gnu.org,
>> google.com, and a few other sites. I could resolve the domain
>> famulari.name, but not another domain that points to the same machine.
>>
>> I installed dig and could successfully query the nameserver described in
>> /etc/resolv.conf for hydra.gnu.org.
>
> Could this be related to cached resolution failures in nscd?  Have you
> tried restarting the nscd service?

That sounds likely.

Nscd caches negative lookups, but normally only for 20 seconds (see
%nscd-minimal-caches in (gnu system install)).  So if you look up
hydra.gnu.org before the network is set up, it’ll remember for 20s that
this is a lookup failure, even if you’ve set up the network in the
meantime.

However, nscd is reportedly behaving strangely:
<http://bugs.gnu.org/20816>.

Do you initially get successful lookups for hydra.gnu.org, and
eventually lookup failures?

Ludo’.