Unbound DNS Cache Fails After Patch 32 on Ubuntu 20

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L. Mark Stone
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Unbound DNS Cache Fails After Patch 32 on Ubuntu 20

Post by L. Mark Stone »

Last night I applied Patch 32 to a multi-server Zimbra system, where some of the hosts were running Linux dnsmasq for local caching and two of the newer mail stores on Ubuntu 20 were running Zimbra's Unbound DNS cache.

Patch 32 installed without errors on all hosts, and Zimbra worked OK immediately afterwards. But this morning we started seeing a large number of "NO_SUCH_BLOB" errors. Similarly, the local monitoring agents on these two mailstores were complaining they couldn't talk to the mothership.

Sure enough, Zimbra's Unbound had stopped resolving queries.

I did as the zimbra user:

Code: Select all

zmdnscachectl stop
zmprov ms `zmhostname` -zimbraServiceEnabled dnscache
and then installed dnsmasq on these two servers. After restarting Zimbra there, and the monitoring agent, everything was nominal once more.

I opened a Support Case as well for this.

zmcontrol -v output:

Code: Select all

Release 8.8.15.GA.4177.UBUNTU20.64 UBUNTU20_64 NETWORK edition, Patch 8.8.15_P32.
Hope that helps others, and that this is fixed in Patch 26/33.

Mark
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L. Mark Stone
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zimico
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Re: Unbound DNS Cache Fails After Patch 32 on Ubuntu 20

Post by zimico »

Thank Mark for your info. I always use named or dnsmasq for our production servers because I had some problems with Zimbra unbound and feel that it is not stable.
Regards,
Minh.
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Re: Unbound DNS Cache Fails After Patch 32 on Ubuntu 20

Post by L. Mark Stone »

Hi Minh!

Hope you and your family are doing well and staying safe!

I think part of the problem is that Zimbra is using Unbound 1.11, which was released in July 2020, whereas the current version is 1.16.0. The changelog (https://nlnetlabs.nl/projects/unbound/d ... und-1-16-0) indicates the interim versions contain a myriad of fixes for memory leaks, SERVFAIL and readagain fails. As Zimbra has made it a priority to upgrade past end-of-life components bundled with Zimbra, hopefully Unbound will get some attention sometime in the next few Patch releases. It is very convenient to use, especially on AWS when using Route 53 private zones for the Zimbra servers.

All the best,
Mark
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L. Mark Stone
Mission Critical Email - Zimbra VAR/BSP/Training Partner https://www.missioncriticalemail.com/
AWS Certified Solutions Architect-Associate
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