Re: Does Postfix cache resolv.conf? [SOLVED]
Christoph Anton Mitterer put forth on 1/11/2010 5:31 PM: Using the resolvconf package, should solve your problems, the Debian postfix package ships rules for resolvconf in order to automatically update the chroot resolv.conf. resolvconf has a long list of conflicts including ifupdown and bind8/9. I've heard of some folks running bind locally on their (large) mail servers for dnsbl lookups (yes, instead of rbldnsd) and other purposes. Would using resolvconf break bind? Aptitude seems to suggest this. Does one need to be extra careful if/when installing this package? What kind of collateral damage does this pagkage cause, if any? Conflicts: bind ( 1:8.3.4-1), bind9 ( 1:9.2.1-7), dhcp-client (= 3.0.1betaRC4-1), dhcp-client ( 2.0pl5-18), dhcp3-client ( 3.0+3.0.1rc11-5), dhcpcd ( 1:1.3.22pl4-7), divine, dnsmasq ( 1.13-2), ifupdown ( 0.6.4-4.1), laptop-net ( 2.21-1), pcmcia-cs ( 3.2.5-1), pdnsd ( 1.1.10par-4), pppconfig ( 2.3.1), pppoeconf ( 1.0), pump ( 0.8.15-1), runit ( 1.8.0-3), totd ( 1.4-4), udhcpc ( 0.9.8cvs20050124-3), webmin ( 1.150-2), webmin-wvdial ( 1.160-3), whereami ( 0.3.3), xisp -- Stan
Re: Does Postfix cache resolv.conf? [SOLVED]
On Tue, 2010-01-12 at 04:02 -0600, Stan Hoeppner wrote: resolvconf has a long list of conflicts including ifupdown and bind8/9. Uhm has it? Would using resolvconf break bind? Unlikely,.. at least I'm using it together with bind9 Aptitude seems to suggest this. Well the resolvconf package conflicts against some specific versions, which were until then not made compatible with it. Does one need to be extra careful if/when installing this package? There's a readme included in the package which lists mist common pitfals, but usually all of them should be fixed in current package versions. What kind of collateral damage does this pagkage cause, if any? Well the worst thing is probably that your resolving doesn't work for some time and you'll have to remove the package again... Cheers, Chris. smime.p7s Description: S/MIME cryptographic signature
Re: Does Postfix cache resolv.conf?
Wietse Venema: Apparently postfix missed the switching of nameservers and did not learn of the new DNS until restart. Is this a bug or a feature? Like most programs, Postfix never reads /etc/resolv.conf. Yes, I suspected that. Instead, that file is read by the NSSWITCH system library functions, and the DNS system library functions. Postfix does not run on bare metal - instead it runs on an operating system that provides libraries and other runtime support. The strange thing is that postfix apparently was the only application on that box, which was unable to resolve names after the change of DNS. Following a restart it worked fine. So it must be something running in the context of postfix, e.g. a library, which causes the problem. I just try to figure out, what postfix does differently as compared to roughly a dozen of other applications, which were subject to the same change of DNS and eventually use the same system libraries. I'm just the kind of guy, who likes to know why something is happening. Since there are a lot of applications inventing wheels (the broken bind9 apparently crashes in its self-made memory manager), knowing that postfix doesn't is a useful input. Thanks a lot. Regards, - lars.
Re: Does Postfix cache resolv.conf? [SOLVED]
Thanks Stefan, The Debian packages of Postfix are running smtpd in a chroot by default. The files necessary for this are copied by the init script /etc/init.d/postfix - and amongst them is the resolv.conf you changed. It's exactly this. The chroot has its own copy of (caches) resolv.conf. Regards, - lars.
Re: Does Postfix cache resolv.conf? [SOLVED]
On Jan 11, 2010, at 4:23 PM, Dr. Lars Hanke wrote: It's exactly this. The chroot has its own copy of (caches) resolv.conf. And the command 'postfix check' will tell you if there's a problem (my server just now): r...@server# postfix check postfix/postfix-script: warning: /var/spool/postfix/etc/hosts and /etc/hosts differ -- Glenn English g...@slsware.com
Re: Does Postfix cache resolv.conf? [SOLVED]
On Tue, 2010-01-12 at 00:23 +0100, Dr. Lars Hanke wrote: Thanks Stefan, The Debian packages of Postfix are running smtpd in a chroot by default. The files necessary for this are copied by the init script /etc/init.d/postfix - and amongst them is the resolv.conf you changed. It's exactly this. The chroot has its own copy of (caches) resolv.conf. Using the resolvconf package, should solve your problems, the Debian postfix package ships rules for resolvconf in order to automatically update the chroot resolv.conf. Cheers, Chris. smime.p7s Description: S/MIME cryptographic signature
Re: Does Postfix cache resolv.conf?
* Dr. Lars Hanke l...@lhanke.de: I had a quite strange issue. About a week ago my bind9 broke down and I could not get it running again on the same machine. So moved it to another machine and changed the /etc/resolv.conf of my machines to try both IP. Apparently everything worked fine. Today I was puzzled that the corresponding bug-report to the Debian list was somehow missing. I resent it watching the postfix logs and found that potfix was missing the MX entry of my relay host and refused to send. Since the host itself actually does not have a MX entry, I was sidetracked assuming postfix was not smart enough to strip the host name from the domain. During this trouble shooting I had postfix reload its configuration a couple of times. After setting the name in [] postfix reported that the A entry was missing, which definitely was wrong. I restarted postfix and voilá it continued working like it did all the years before. Now I know that it is smart enough to strip the relay host name from the domain to lookup MX. ;) Apparently postfix missed the switching of nameservers and did not learn of the new DNS until restart. Is this a bug or a feature? Postfix Version: 2.5.5 (Current Debian stable) The Debian packages of Postfix are running smtpd in a chroot by default. The files necessary for this are copied by the init script /etc/init.d/postfix - and amongst them is the resolv.conf you changed. I guess what happened is: 1. You didn't disable smtpd's chroot in master.cf. 2. You changed /etc/resolv.conf without copying it to the chroot. 3. You restarted Postfix using Debian's init script which copied the changed resolv.conf file to the chroot. Stefan
Re: Does Postfix cache resolv.conf?
On Sun, 10 Jan 2010 11:32:34 +0100 Dr. Lars Hanke l...@lhanke.de wrote: I had a quite strange issue. About a week ago my bind9 broke down and I could not get it running again on the same machine. So moved it to another machine and changed the /etc/resolv.conf of my machines to try both IP. Apparently everything worked fine. Today I was puzzled that the corresponding bug-report to the Debian list was somehow missing. I resent it watching the postfix logs and found that potfix was missing the MX entry of my relay host and refused to send. Since the host itself actually does not have a MX entry, I was sidetracked assuming postfix was not smart enough to strip the host name from the domain. During this trouble shooting I had postfix reload its configuration a couple of times. After setting the name in [] postfix reported that the A entry was missing, which definitely was wrong. I restarted postfix and voilá it continued working like it did all the years before. Now I know that it is smart enough to strip the relay host name from the domain to lookup MX. ;) Apparently postfix missed the switching of nameservers and did not learn of the new DNS until restart. Is this a bug or a feature? This is true of most services, not just postfix. They will read /etc/resolv.conf at startup and not again unless told to do so -- John
Re: Does Postfix cache resolv.conf?
Dr. Lars Hanke: Apparently postfix missed the switching of nameservers and did not learn of the new DNS until restart. Is this a bug or a feature? Like most programs, Postfix never reads /etc/resolv.conf. Instead, that file is read by the NSSWITCH system library functions, and the DNS system library functions. Postfix does not run on bare metal - instead it runs on an operating system that provides libraries and other runtime support. Wietse
