At Fri, 24 May 2024 09:20:44 -0700 CentOS mailing list discuss@lists.centos.org 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.