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c12s-kubespray/docs/dns-stack.md
Bogdan Dobrelya 82ee60fe8b Make dnsmasq daemon set optional 
Change additional dnsmasq opts:
- Adjust caching size and TTL
- Disable resolve conf to not create loops
- Change dnsPolicy to default (similarly to kubedns's dnsmasq). The
  ClusterFirst should not be used to not create loops
- Disable negative NXDOMAIN replies to be cached
- Make its very installation as optional step (enabled by default).
  If you don't want more than 3 DNS servers, including 1 for K8s, disable
  it.
- Add docs and a drawing to clarify DNS setup.
- Fix stdout logs for dnsmasq/kubedns app configs
- Add missed notifies to resolvconf -u handler
- Fix idempotency of resolvconf head file changes

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
2016-09-23 12:59:06 +02:00

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K8s DNS stack by Kargo

Here is an approximate picture of how DNS things working and being configured by Kargo ansible playbooks:

Image

Note that an additional dnsmasq daemon set is installed by Kargo by default. Kubelet will configure DNS base of all pods to use that dnsmasq cluster IP. You can disable it with the skip_dnsmasq var. This may be the case, if you're fine with Linux limit of max 3 nameservers in the /etc/resolv.conf. When skipped and bypassed directly to Kubedns's dnsmasq cluster IP, it greatly simplifies things by the price of limited nameservers though.

Nameservers are configured in the hosts' /etc/resolv.conf files from the nameservers (see also searchdomains) vars. While the upstream_dns_servers will define additional DNS servers for the dnsmasq daemon set running on all hosts (unless bypassed with skip_dnsmasq).