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Fix DNS documents to remove references to DNS as an optional addon.

This commit is contained in:
Girish Kalele 2016-06-27 16:13:11 -07:00
parent 0e49d214f9
commit c634053ec1
1 changed files with 19 additions and 17 deletions
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36
docs/admin/dns.md
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@ -1,8 +1,10 @@
---
---
As of Kubernetes 0.8, DNS is offered as a [cluster add-on](http://releases.k8s.io/{{page.githubbranch}}/cluster/addons/README.md).
If enabled, a DNS Pod and Service will be scheduled on the cluster, and the kubelets will be
## Introduction
As of Kubernetes 1.3, DNS is a built-in service launched automatically using the addon manager [cluster add-on](http://releases.k8s.io/{{page.githubbranch}}/cluster/addons/README.md).
A DNS Pod and Service will be scheduled on the cluster, and the kubelets will be
configured to tell individual containers to use the DNS Service's IP to resolve DNS names.
Every Service defined in the cluster (including the DNS server itself) will be
@ -15,25 +17,25 @@ in namespace `bar` can look up this service by simply doing a DNS query for
`foo`. A Pod running in namespace `quux` can look up this service by doing a
DNS query for `foo.bar`.
The cluster DNS server ([SkyDNS](https://github.com/skynetservices/skydns))
supports forward lookups (A records) and service lookups (SRV records).
The Kubernetes cluster DNS server (based off the [SkyDNS](https://github.com/skynetservices/skydns) library)
supports forward lookups (A records), service lookups (SRV records) and reverse IP address lookups (PTR records).
## How it Works
The running DNS pod holds 4 containers - skydns, etcd (a private instance which skydns uses),
a Kubernetes-to-skydns bridge called kube2sky, and a health check called healthz. The kube2sky process
watches the Kubernetes master for changes in Services, and then writes the
information to etcd, which skydns reads. This etcd instance is not linked to
any other etcd clusters that might exist, including the Kubernetes master.
The running Kubernetes DNS pod holds 3 containers - kubedns, dnsmasq and a health check called healthz.
The kubedns process watches the Kubernetes master for changes in Services and Endpoints, and maintains
in-memory lookup structures to service DNS requests. The dnsmasq container adds DNS caching to improve
performance. The healthz container provides a single health check endpoint while performing dual healthchecks
(for dnsmasq and kubedns).
## Issues
## Kubernetes Federation (Multiple Zone support)
The skydns service is reachable directly from Kubernetes nodes (outside
of any container) and DNS resolution works if the skydns service is targeted
explicitly. However, nodes are not configured to use the cluster DNS service or
to search the cluster's DNS domain by default. This may be resolved at a later
time.
The 1.3 release introduced Federation (Ubernetes) support for multisite Kubernetes installations. There are
DNS changes introduced that will allow the lookup of services using a six part DNS name.
See [Federation docs](/docs/admin/multiple-zones/) for more details on multiple site support.
## For more information
## References
- [Docs for the DNS cluster addon](http://releases.k8s.io/{{page.githubbranch}}/cluster/addons/dns/README.md)
See [the docs for the DNS cluster addon](http://releases.k8s.io/{{page.githubbranch}}/cluster/addons/dns/README.md).