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How disable powerdns in microbosh and bosh ?
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Hi,
I understand that by default the micro-bosh has DNS enabled (i.e. hosts a powerDNS servers that gets injected by default in all VMs it manages). If the dns entry [1] is specified, additional DNS resolvers will be added to /etc/resolv.conf and the micro bosh powerDNS will remain (at the end as the last fallback ?) When micro-bosh is only used to instanciate a multi-vm bosh instance which does not rely on FQDN but rather on IP addresses, then it would make sense to disable DNS on microbosh to avoid bosh failing to resolve Iaas FQDN in case microbosh is down. On a multi-vm bosh cluter, it seems the power DNS would be disabled if any of the necessary dns property is missing [3], even through spec file [2] isn't explicit about it. I however wonder what's the best way to disable the DNS job in the micro-bosh, as the dns properties are typically not set in the microbosh manifest. Searching through forums I only found [4] mentionning specifying the "dynamic" type for the micro-bosh network implicitly disables the powerDNS job. I don't understand why there is a link between the two. Is there a more explict way to configure micro-bosh DNS ? Where are director properties [2] default values for micro set, and can they be overriden from the manifest file ? I tried assigning an empty dns.adress in the micro bosh manifest, but the bosh micro cli did not pick the modification "Will skip deploy due to no changes". Am I on the right track ? apply_spec: properties: dns: #Define an empty DNS address to disable the microbosh power DNS running by default. address: I tried looking at the concourse pipeline config and resources to get inspiration but could not find related bosh config yet. Thanks in advance, Guillaume. [0] https://bosh.io/docs/create-micro-manifest.html *MicroBOSH has a nameserver component called powerDNS. If, after you deploy MicroBOSH, you use it deploy other software, MicroBOSH will create VMs as it deploys that software. VMs that MicroBOSH creates use the powerDNS on their parent VM to resolve IP addresses.* [1] http://bosh.io/docs/networks.html [2] https://github.com/cloudfoundry/bosh/blob/05806e445d4784b5c44721dfe7dc89aeb353de66/release/jobs/director/spec#L149 [3] https://github.com/cloudfoundry/bosh/blob/7cd8b976a0489e47947c7f9ffc1c2db77dc5e3da/release/jobs/director/templates/director.yml.erb.erb#L67-L84 [4] https://groups.google.com/a/cloudfoundry.org/d/msg/bosh-users/6lfnOXMlBEU/hAJiewKL7wAJ |
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Pablo Alonso Rodriguez <palonsoro@...>
Hi.
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If you are trying to unset dns properties, maybe this might work (at least, DNS properties should not be set at director.yml): apply_spec: properties: dns: null However, as far as I have seen, microbosh DNS is set as the last entry at resolv.conf. According to the MAN page ( http://man7.org/linux/man-pages/man5/resolv.conf.5.html), it should be the last server tried. Furthermore, if all the servers fail, all the servers are retried again in the same order. Thus, I think that having microbosh in the last place of resolv.conf should not disturb you even if microbosh VMs crashes, provided that you have set other DNS servers in the networks section of your deployment manifest. The DNS servers that you provide should be tried in the first place and should be retried if there is a temporary network issue. 2015-06-17 13:22 GMT+02:00 Guillaume Berche <bercheg(a)gmail.com>: Hi, |
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Thanks a lot Pablo Alonso for your response and for your analysis that
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microbosh DNS is always placed at end of the resolv.conf and hence should not harm bosh resolution w.r.t. explicitly configured DNS resolvers. I'll try the null syntax out of curiosity. Guillaume. On Wed, Jun 17, 2015 at 3:03 PM, Pablo Alonso Rodriguez <palonsoro(a)gmail.com
wrote: Hi. |
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