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

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This reverts commit 8b3359f75d.
This commit is contained in:
Girish Kalele
2016-06-27 16:14:21 -07:00
parent 8b3359f75d
commit 0e49d214f9
1 changed files with 15 additions and 14 deletions
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docs/admin/dns.md
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--- ---
--- ---
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). As of Kubernetes 0.8, DNS is offered as a [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 If enabled, 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
@@ -15,24 +15,25 @@ 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 Kubernetes cluster DNS server (based off the [SkyDNS](https://github.com/skynetservices/skydns) library) The cluster DNS server ([SkyDNS](https://github.com/skynetservices/skydns))
supports forward lookups (A records), service lookups (SRV records) and reverse IP address lookups (PTR records). supports forward lookups (A records) and service lookups (SRV records).
## How it Works ## How it Works
The running Kubernetes DNS pod holds 3 containers - kubedns, dnsmasq and a health check called healthz. The running DNS pod holds 4 containers - skydns, etcd (a private instance which skydns uses),
The kubedns process watches the Kubernetes master for changes in Services and Endpoints, and maintains a Kubernetes-to-skydns bridge called kube2sky, and a health check called healthz. The kube2sky process
in-memory lookup structures to service DNS requests. The dnsmasq container adds DNS caching to improve watches the Kubernetes master for changes in Services, and then writes the
performance. The healthz container provides a single health check endpoint while performing dual healthchecks information to etcd, which skydns reads. This etcd instance is not linked to
(for dnsmasq and kubedns). any other etcd clusters that might exist, including the Kubernetes master.
## Issues ## Issues
The 1.3 release introduced Federation (Ubernetes) support for multisite Kubernetes installations. There are The skydns service is reachable directly from Kubernetes nodes (outside
DNS changes introduced that will allow the lookup of services using a six part DNS name. of any container) and DNS resolution works if the skydns service is targeted
See [Federation docs](https://kubernetes.github.io/docs/admin/multiple-zones.md) 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.
## For more information ## For more information
See [the 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).