From 0e49d214f907db101deaa1626fca687c81a0c583 Mon Sep 17 00:00:00 2001 From: Girish Kalele Date: Mon, 27 Jun 2016 16:14:21 -0700 Subject: [PATCH] Revert "Fix DNS documents to remove references to DNS as an optional addon." This reverts commit 8b3359f75d2884ed03aa05b498212419ec2d90db. --- docs/admin/dns.md | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/docs/admin/dns.md b/docs/admin/dns.md index d173e6813e..2e37cdaf83 100644 --- a/docs/admin/dns.md +++ b/docs/admin/dns.md @@ -1,8 +1,8 @@ --- --- -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 +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 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 @@ -15,24 +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 DNS query for `foo.bar`. -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). - +The cluster DNS server ([SkyDNS](https://github.com/skynetservices/skydns)) +supports forward lookups (A records) and service lookups (SRV records). ## How it Works -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). +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. ## Issues -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](https://kubernetes.github.io/docs/admin/multiple-zones.md) +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. ## 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). \ No newline at end of file