At Fri, 24 May 2024 09:20:44 -0700 CentOS mailing list <discuss@xxxxxxxxxxxxxxxx> wrote:
>
> I asked:
>
> > I have a CentOS stream 8 system (C8) which runs its own internal
> > name server (BIND 9). In the past, it used an external name server
> > on another machine but that server has been stopped. The resolv.conf
> > file on C8 has been modified to remove the reference to the old
> > server and NetworkManager has been restarted. However, CUPS and
> > other programs on C8 continue to send queries to the old server,
> > all of which eventually time out (of course). The bogus queries to
> > the old server are answered with ICMP destination/port unreachable,
> > confirming that the old name server is not running. But these bogus
> > queries take time and the delays are very annoying.
> >
> > I've also restarted CUPS without effect. There are no references to the
> > old server in /etc/named.conf, but there are references to the subnet
> > it was on as there are other machines there that need to use the new
> > name server. I haven't yet rebooted C8 but I'm prepared if necessary.
> >
> > Is there something else I should do before rebooting C8? Is that even
> > likely to solve the problem?
>
> Aleksandar Ivanisevic wrote:
>
> > Do you have nscd running? Try restarting that.
>
> Simon Matter wrote:
>
> > Doesn't systemd do some kind of its own name resolution thing these days?
> >
> > Maybe someone else can say more about this.
>
> Thanks. But nscd is not running. Perusing all the active systemd
> services, I restarted systemd-resolved and systemd-networkd but that
> doesn't seem to have had any effect.
I have found that systemd-resolved is sometimes "fishy" if you are trying to
use a local Bind9 name server. systemd-resolved is way too "clever" for its
own good. Maybe that is a good thing in some cases, but I have found it
problematical for a LAN with a "real" (eg bind9) name server providing names
for local machines.
Normally, with systemd-resolved running /etc/resolv.conf is NOT an editable
file, but a symlink to a file under systemd-resolved control, and usually
systemd-resolved is running its own caching only name server (dmasq?) that is
caching 8.8.8.8 -- eg none of the local network machines are DNS resolved
(which is fine on an ad-hoc LAN). At least that is what happens by default
under Ubuntu. I found it easier to just stop and disable systemd-resolved and
then manually edit /etc/resolv.conf to reference the local Bind9 name server
when I set up a LAN with a local Bind9 name server.
--
Robert Heller -- Cell: 413-658-7953 GV: 978-633-5364
Deepwoods Software -- Custom Software Services
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