[GTALUG] SystemD vs Bind9 vs IPv6

Christopher Browne cbbrowne at gmail.com
Thu Oct 16 13:59:47 UTC 2014


I think I got bit yesterday by the above...

I was noticing terrible resolution speed, so checked messages (btw,
"service bind9 status" provides brief, but decent-ish characterization of
things), and noticed many messages indicating failing resolutions against
IPv6 addresses.

There is a common pair of bits of Bind configuration:
a) One might set options to prefer not to use IPv6 addresses, so in
/etc/bind/named.conf.options, change
   listen-on-v6 { all;};
to
   listen-on-v6 { none; };

b) This was where SystemD got into the mix...

Pass the "-4" option when running named to use only IPv4.  This seems to be
the highly significant bit.

On Debian-derived systems, the usual recipe is to add "-4" to
/etc/defaults/bind
  --> OPTIONS="-4"

However, the SystemD config for Bind9 lives in
/lib/systemd/system/bind9.service, and apparently there is recent change
there that that configuration no longer reads from /etc/defaults/bind, so
that to have named get the "-4" option requires altering
/lib/systemd/system/bind9.service.  Seems like it needs to be altered
directly.

This isn't necessarily a "SystemD bug", rather a packaging bug in Debian.
It still was fairly annoying.

I have yet to report it properly, probably deserves a bit more research, in
case my diagnosis is off a bit.

-- 
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"
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