On Wed, 25.03.15 04:20, Mikhail Morfikov (mmorfi...@gmail.com) wrote: > In the systemd-resolved manual we can read something like this: > > The DNS servers contacted are determined from the global settings in > resolved.conf(5), the per-link static settings in .network files, and > the per-link dynamic settings received over DHCP. > > 1. Let's say that I have set all the three settings, which one will be > applied?
Per-interface DHCP acquired DNS servers take precedence over manually configured per-interface DHCP servers. Global settings are used only if no per-interface DNS server settings are known. > 2. If I set the global settings via the /etc/systemd/resolved.conf file, > for instance: > > [Resolve] > DNS=127.0.2.1 > FallbackDNS=208.67.222.222 208.67.220.220 > > will this local resolver be used all the time, even when dhcp > server sends an ip address of other resolver in the network to > the client? No. It is only used if no per-interface DNS servers are known. They always take precedence. In this case FallbackDNS= is without effect, since it is only used if no other DNS servers is configured. In fact FallbackDNS= only makes sense if you leave DNS= empty in which case it is read from /etc/resolv.conf instead. In that case FallbackDNS= is used when /etc/resolv.conf is missing or contains no entries. > So UseDNS is set to false, and I thought the system will be using > the local resolver, but it sometimes uses the local settings and > sometimes not -- it depends on restarting the systemd-resolved > service, for example: You need to set UseDNS= to false and DNS= to the empty list in the interface file. Use "networkctl status -a" to check which per-interface DNS servers are being used. > # ls -al /etc/resolv.conf > lrwxrwxrwx 1 root root 32 2015-02-27 23:52:39 /etc/resolv.conf -> > /run/systemd/resolve/resolv.conf > > # cat /etc/resolv.conf > nameserver 127.0.2.1 > nameserver 192.168.1.1 > search mhouse.lh > > # systemctl restart systemd-resolved.service > # cat /etc/resolv.conf > nameserver 192.168.1.1 > nameserver 127.0.2.1 > search mhouse.lh > > (I've cut the comments for readability) Ah, this is actually a bug. The order wasn't stable. I fixed that now: http://cgit.freedesktop.org/systemd/systemd/commit/?id=822db23cfa98a9fbc48f41e11caafb6f1017e052 > 3. Shouldn't there be just one resolver in the /etc/resolv.conf > file? We write the global servers out first, followed by the per-interface ones. > 4. How to force the system to use the one particular resolver no matter > what? I know I could probably do that by creating a static file instead > of a link (and maybe chattr +i if necessary), but I want to do this > using the systemd native tools if that is possible of course. Turn off UseDNS= for all interfaces and set DNS= for them to the empty string. > 5. Is the /etc/resolv.conf file necessary when using systemd? Nope. Not if you list "resolve" instead of "dns" in your nsswitch.conf. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
