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Merge pull request #742 from girishkalele/dns_doc_fixup

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Fix DNS documents to remove references to DNS as an optional addon.
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johndmulhausen
2016-06-29 15:25:48 -07:00
committed by GitHub
parent 64b6a65de5 c634053ec1
commit 89ea52c058
1 changed files with 19 additions and 17 deletions
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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). ## Introduction
If enabled, a DNS Pod and Service will be scheduled on the cluster, and the kubelets will be
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. 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 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 `foo`. A Pod running in namespace `quux` can look up this service by doing a
DNS query for `foo.bar`. DNS query for `foo.bar`.
The cluster DNS server ([SkyDNS](https://github.com/skynetservices/skydns)) The Kubernetes cluster DNS server (based off the [SkyDNS](https://github.com/skynetservices/skydns) library)
supports forward lookups (A records) and service lookups (SRV records). supports forward lookups (A records), service lookups (SRV records) and reverse IP address lookups (PTR records).
## How it Works ## How it Works
The running DNS pod holds 4 containers - skydns, etcd (a private instance which skydns uses), The running Kubernetes DNS pod holds 3 containers - kubedns, dnsmasq and a health check called healthz.
a Kubernetes-to-skydns bridge called kube2sky, and a health check called healthz. The kube2sky process The kubedns process watches the Kubernetes master for changes in Services and Endpoints, and maintains
watches the Kubernetes master for changes in Services, and then writes the in-memory lookup structures to service DNS requests. The dnsmasq container adds DNS caching to improve
information to etcd, which skydns reads. This etcd instance is not linked to performance. The healthz container provides a single health check endpoint while performing dual healthchecks
any other etcd clusters that might exist, including the Kubernetes master. (for dnsmasq and kubedns).
## Issues ## Kubernetes Federation (Multiple Zone support)
The skydns service is reachable directly from Kubernetes nodes (outside The 1.3 release introduced Federation (Ubernetes) support for multisite Kubernetes installations. There are
of any container) and DNS resolution works if the skydns service is targeted DNS changes introduced that will allow the lookup of services using a six part DNS name.
explicitly. However, nodes are not configured to use the cluster DNS service or See [Federation docs](/docs/admin/multiple-zones/) for more details on multiple site support.
to search the cluster's DNS domain by default. This may be resolved at a later
time.
## 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).