I come back to a message that just help me with a server:
>Dominic Hargreaves a écrit : >> >> I did just notice that there is a third state that the file sometimes >> ends up in, as well as the expected one which begins "Generated by >> Network Manager". This is a file which just contains one nameserver >> entry containing the IPv6 resolver. Odd. > > That may be generated from received IPv6 router advertisements (RA) by > rdnssd if installed. In that case, you can remove this package if you > don't need DNS resolution through the IPv6 server. Otherwise, check > whether the package resolvconf is installed.It could be good to have this package, rdnssd, mentionned in this doc:
among the packages that can alter /etc/resolv.conf
Indeed, I guess rdnssd was recently added to debian stable, I presume it is not very well known, but it's installed by default.
In my case, installing a virtual server in a quite common and tested environnement, just for the first time with debian 8.4, I came up with a server that simply had no DNS resolution, and no way to solve the problem with the classic static /etc/resolv.conf, or debconf parameters in /etc/network/interfaces.
I understand it's because the router where this server is connected is partially IPv6 aware (connected to an IPv6 network, but without IPv6 configured). This package detects some kind of IPv6 dns, and starts overwtitting /etc/resolv.conf. But it was quite hard to find the trick. Most documentation about /etc/resolv.conf overwrite problems propose hooks and workarounds.
I'm new in this list (it's why I copy/paste the meesage I reference). Sorry if there is a better place for this comment that I missed.