Mesos allows dynamic sharing of cluster resources between Kubernetes and other first-class Mesos frameworks such as [Hadoop][1], [Spark][2], and [Chronos][3].
Mesos clusters can be deployed on nearly every IaaS cloud provider infrastructure or in your own physical datacenter. Kubernetes on Mesos runs on-top of that and therefore allows you to easily move Kubernetes workloads from one of these environments to the other.
Update your PATH to more easily run the Kubernetes-Mesos binaries:
```bash
$ export PATH="$(pwd)/_output/local/go/bin:$PATH"
```
Identify your Mesos master: depending on your Mesos installation this is either a `host:port` like `mesos_master:5050` or a ZooKeeper URL like `zk://zookeeper:2181/mesos`.
In order to let Kubernetes survive Mesos master changes, the ZooKeeper URL is recommended for production environments.
```bash
$ export MESOS_MASTER=<host:portorzk://url>
```
Create a cloud config file `mesos-cloud.conf` in the current directory with the following contents:
```bash
$ cat <<EOF>mesos-cloud.conf
[mesos-cloud]
mesos-master = ${MESOS_MASTER}
EOF
```
Now start the kubernetes-mesos API server, controller manager, and scheduler on the master node:
Kube-dns is an addon for Kubernetes which adds service discovery to the cluster. For a detailed explanation see [DNS in Kubernetes][4].
The kube-dns addon runs as a pod inside the cluster. The pod consists of three co-located containers:
- a local etcd instance
- the [skydns][11] DNS server
- the kube2sky process to glue skydns to the state of the Kubernetes cluster.
The skydns container offers DNS service via port 53 to the cluster. The etcd communication works via local 127.0.0.1 communication
We assume that kube-dns will use
- the service IP `10.10.10.10`
- and the `cluster.local` domain.
Note that we have passed these two values already as parameter to the apiserver above.
A template for an replication controller spinning up the pod with the 3 containers can be found at [cluster/addons/dns/skydns-rc.yaml.in][11] in the repository. The following steps are necessary in order to get a valid replication controller yaml file:
- replace `{{ pillar['dns_replicas'] }}` with `1`
- replace `{{ pillar['dns_domain'] }}` with `cluster.local.`
- add `--kube_master_url=${KUBERNETES_MASTER}` parameter to the kube2sky container command.
In addition the service template at [cluster/addons/dns/skydns-svc.yaml.in][12] needs the following replacement:
Check with `kubectl get pods --namespace=kube-system` that 3/3 containers of the pods are eventually up and running. Note that the kube-dns pods run in the `kube-system` namespace, not in `default`.
To check that the new DNS service in the cluster works, we start a busybox pod and use that to do a DNS lookup. First create the `busybox.yaml` pod spec:
```bash
cat <<EOF>busybox.yaml
apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: default
spec:
containers:
- image: busybox
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
name: busybox
restartPolicy: Always
EOF
```
Then start the pod:
```bash
kubectl create -f busybox.yaml
```
When the pod is up and running, start a lookup:
```bash
kubectl exec busybox -- nslookup kubernetes
```
If everything works fine, you will get this output:
