[CentOS] Could not resolve host: mirror.centos.org

Александр Кириллов писал 2014-09-06 18:32:
>>> There seems to be a problem with my local dns server resolving
>>> mirror.centos.org.
>>> I know something about dns but obviously not enough to figure out 
>>> what
>>> might be wrong here or how to fix
>>> this in bind configs. The SERVFAIL errors below seem to be related to
>>> AAAA and MX queries for the domain.
>>> Please advise. TIA.
>>> 
>>> 
>>> # host mirror.centos.org 8.8.8.8
>>> Using domain server:
>>> Name: 8.8.8.8
>>> Address: 8.8.8.8#53
>>> Aliases:
>>> 
>>> mirror.centos.org has address 69.167.139.9
>>> 
>>> 
>>> # host mirror.centos.org
>>> mirror.centos.org has address 66.109.26.212
>>> Host mirror.centos.org not found: 2(SERVFAIL)
>>> Host mirror.centos.org not found: 2(SERVFAIL)
>>> 
>>> 
>>> # tail -F /var/named/chroot/var/named/data/named.run
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 85.12.30.226#53
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 93.113.36.66#53
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 94.46.190.42#53
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 85.12.30.226#53
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 93.113.36.66#53
>>> error (FORMERR) resolving 'mirror.centos.org/AAAA/IN': 
>>> 94.46.190.42#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 85.12.30.226#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 93.113.36.66#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 94.46.190.42#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 85.12.30.226#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 93.113.36.66#53
>>> error (FORMERR) resolving 'mirror.centos.org/MX/IN': 94.46.190.42#53
>>> 
>> 
>> Try asking the correct type (A record only) and you'll have the 
>> correct
>> answer : the three PDNS servers having delegation for 
>> mirror.centos.org
>> will only answer for A records (we have obviously no MX record for
>> mirror.centos.org and, unfortunately, no AAAA records for those 
>> machines
>> either)
>> 
>> PS : host is considered "deprecated" so switch to dig instead ? ;-)
> 
> Thanks for your answer, Fabian,
> I forgot to mention in the OP that the source of the error is yum with
> scl repo enabled:
> 
> # yum distro-sync
> Loaded plugins: fastestmirror, priorities, refresh-packagekit, 
> security, verify
> ...
> http://mirror.centos.org/centos/6/SCL/x86_64/repodata/repomd.xml:
> [Errno 14] PYCURL ERROR 6 - "Could not resolve host: mirror.centos.org
> (Could not contact DNS servers)"
> Trying other mirror.
> Error: Cannot retrieve repository metadata (repomd.xml) for
> repository: scl. Please verify its path and try again

This is an ipv6-enabled system and that's probably why yum tries to get 
an ipv6 address first for mirror.centos.org and fails miserably. For 
whatever reason I do not get an authoritative negative response for AAAA 
query from upstream servers. Well an easy fix is to hardcode an ipv4 
address for mirror.centos.org in /etc/hosts and forget it. I suspect 
miconfiguration on centos.org side as scl is the only  repo which gives 
me troubles but don't have the time to dig into this.