On Fri, Feb 19, 2021 at 11:25:43AM +0000, Chris Green wrote:
On Fri, Feb 19, 2021 at 10:16:25AM +0000, Mark Rogers wrote:
I have an Ubuntu 18.04 server running VirtualMin.
I logged in today to do routine updates to discover it has lost its ability to resolve DNS queries. The server otherwise seems fine but I can't update it.
/etc/resolv.conf tells me that it's using 127.0.0.53 for DNS, which is systemd-resolvd.
systemd-resolve --status lists no nameservers, which will be where my problem is, but I work out where that information should come from.
I temporarily set Google DNS in resolv.conf and did the updates, but a reboot restored the 127.0.0.53 DNS configuration (as expected) and the problem is back.
I *think* VirtualMin is a red herring (it's not used for much and I've been planning to decommission it for years but not today!), and in any case it's just a glorified configuration tool with a GUI so any relevant settings should still be hiding under /etc somewhere, but where I have no idea. Suggestions?
The systemd implementation of resolv[conf] is, IMHO, a real can of worms. I've had various DNS issues on my little home LAN ever since systemd got involved with it. None of the issues I've had have been show stoppers but they have been annoying, e.g. failing to return address for short local names, a long delay for the first request, etc.
In the end I turned off the systemd caching DNS (i.e. the one on 127.0.0.53) and now rely solely on dnsmasq running on a Raspberry Pi on my LAN.
My /etc/resolv.conf on my LAN systems is now:-
nameserver 192.168.1.2 search zbmc.euSadly I can't immediately remember what configuration changes I made to do this. If you want details I'm sure I can dig them out, it'll just take a bit of digging into the resolv.conf setup.
A short look and it turns out to be *fairly* simple. If you change the symbolic link for /etc/resolv.conf from the default:-
/run/systemd/resolve/stub-resolv.conf
to:
/run/systemd/resolve/resolv.conf
Then searches will bypass the local cached DNS.
The man page for systemd-resolved does explain it all but in a very confusing way!