Re: systemd.resolved problems
On Fri 25 Mar 2022 at 07:59:15 (+0800), Jeremy Ardley wrote:
> On 25/3/22 7:26 am, Greg Wooledge wrote:
> > On Fri, Mar 25, 2022 at 06:51:55AM +0800, Jeremy Ardley wrote:
> > > I've been having continual problems with postfix and errors in the mail
> > > log about unresolved MX and A records. Not all the time but often
> > > enough to be annoying. I discovered postfix was using the
> > > systemd.resolved server for DNS.
It was consistently AAAA records causing the holdup in my log:
https://lists.debian.org/debian-user/2022/03/msg00656.html
> > > I did some experiments with resolvectl and there were serious delays
> > > looking up sites or just plain failures. In comparison my bind9 instance
> > > never had a problem and returned instantly. ( systemd.resolved used the
> > > same forwarders as my bind9 )
The same here. The delay was often /after/ the lookup had succeeded,
but meant that you didn't get back to the prompt until a timeout expired.
(I was comparing with resolvconf.)
> > > Is there any compelling reason to use systemd.resolved over ordinary DNS ?
> > > If not, why was it inflicted on debian?
> > It's disabled by default. It's there if you wish to try it, but out of
> > the box, it does absolutely nothing except sit there taking up space.
>
> Are you sure it's disabled by default? I don't recall converting over
> to it on my various machines. And when I search on it there are lots
> of pages about how to disable it, and virtually none on how to enable
> it.
>
> I thought there might be some voodoo reason to do with something
> called dbus - of which I know nothing, nor the obscure journald.
The same thread as above comments on the surprise prevention of
renaming the wireless interface caused by merely installing iwd:
https://lists.debian.org/debian-user/2022/03/msg00727.html
If you then go ahead and configure it, the default resolver is set
to systemd-resolved. If you don't create the symlink necessary for
that to work, /etc/resolv.conf remains empty.
So there do appear to be some gotchas in play nowadays.
> Anyway, bind9 works pretty well as a local caching nameserver
I'm sticking with resolvconf for the time being.
Cheers,
David.
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