Kubernetes & Docker examples at Nucleus

We run a fairly default Kubernetes installation in our VMware environment. Most of the Kubernetes documentation also applies to our setup.

It is highly recommended to read about the concepts and tasks section of the Kubernetes docs before continueing.

Your Kubernetes configuration

Our support department will give you your Kubernetes configuration file, tailored to your setup.

To see an example, have a look in kubetl.config-example.

Once you have your configuration, save it on your local machine as kubectl.config.

Talk to your Kubernetes cluster

With a working config, you can now talk to your Kubernetes cluster via the CLI by referencing your configuration file.

$ kubectl --kubeconfig=kubectl.config get services
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.248.0.1   <none>        443/TCP   1d

You can run multiple clusters by referencing a different config file with ---kubeconfig for your kubectl command.

Persistent storage in Kubernetes

The persistence layer is handled by VMware. Creating a persistent volume consists of 2 steps.

First, create a persistent volume claim.

---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: mariadb-pv-claim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 3Gi

The above example will create a persistent volume named mariadb-pv-storage that is 3GB in size.

You'll want to consider a long-term naming scheme for your persistent volumes before you start creating new volumes.

To use this storage claim, your config will look like this.

---
apiVersion: v1
kind: ReplicationController
metadata:
  name: mariadb-rc
spec:
  replicas: 1
  selector:
    app: mariadb
  template:
    metadata:
      name: mariadb-rc
      labels:
        app: mariadb
    spec:
      volumes:
      - name: mariadb-pv-storage
        persistentVolumeClaim:
          claimName: mariadb-pv-claim
      containers:
      - name: mariadb
        image: mariadb:latest
        ports:
        - containerPort: 3306
        volumeMounts:
        - mountPath: "/var/lib/mysql"
          name: mariadb-pv-storage

In this example, the following lines are the most important:

    spec:
      volumes:
      - name: mariadb-pv-storage
        persistentVolumeClaim:
          claimName: mariadb-pv-claim
      containers:
        volumeMounts:
        - mountPath: "/var/lib/mysql"
          name: mariadb-pv-storage

This uses the previously claimed space and mounts it on /var/lib/mysql inside your mariadb container.