In this post, we will see few points to make your Kubernetes experience easier, secure and reproducible, especially on premise cluster.

I- Deploy using helm

Helm is described as a packets manager for Kubernetes. It allows you to package all your application specifications to easily redeploy on any cluster.

A basic helm repository is composed by :

  • Charts.yaml for the name, tags and version of your application
  • templates/ is the folder where you put all your Kubernetes .yaml files (deployments, services, ingresses...)
  • values.yaml is a key-value .yaml file where you put all the variables that you want to use in your templates' files.

For example, if you got this values.yaml : 

global:  
  dbName: test
  dbPassword: xahc5Ceej2keekoo

You can use theses variables in your templates/mysql-deployment.yaml file :

apiVersion: v1  
kind: Deployment  
apiVersion: extensions/v1beta1  
metadata:  
  name: mysql
  namespace: default
  labels:
    k8s-app: mysql
spec:  
  replicas: 1
  selector:
    matchLabels:
      k8s-app: mysql
  template:
    metadata:
      labels:
        k8s-app: mysql
    spec:
      containers:
      - image: mysql:latest
        name: mysql
        imagePullPolicy: Always
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: {{ .Values.global.dbPassword }}
        - name: MYSQL_DATABASE
          value: {{ .Values.global.dbName }}

To install your own helm chart, you can use this command : 

helm install --name=my-chart /chart-folder

If you make a change in your chart (manually or via CI), you can update it with this command : 

helm upgrade my-chart /chart-folder

II- Expose your services with Ingresses

There are many ways to expose a service in a Kubernetes cluster. If you don't use a cloud hosted cluster, you couldn't use the LoadBalancer type because nobody will provide you a public IP address.

The best way, for me, in a production-wide cluster, is to use an Ingress Controller like Nginx Ingress and to expose it via service's External IPs.

To make it possible, you need to route a public (or private) IP range on your k8s' workers and then you can create services like this : 

apiVersion: v1  
kind: Service  
metadata:  
  labels:
    svc: controller
  name: controller
  namespace: default
spec:  
  clusterIP: 10.32.35.129
  externalIPs:
  - 101.5.124.76
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8888
  selector:
    svc: controller
  type: ClusterIP

The external IP is then caught by workers' IPTables who NAT the traffic to the final Pod. If you do this for your Nginx Ingress service, you can now expose all your internal services behind one unique public IPv4 (and IPv6 soon).

If you think about High-availability, you need to share an IP between all your k8s workers (like keepalived) to route your Public IP's to it. (only on premise cluster).

III- Use TLS everywhere

To make your internal cluster communications' secures, it's a good point to use TLS in every deployment you create.

The first point is to expose your pod's service with TLS directly, so if you use a http only server in your container, why not configure TLS with embedded certificates.

The last point is to expose your TLS service to the Internet with full TLS encryption. So if you use an Ingress controller to expose your service, you need to create first, a TLS secret : 

kubectl -n default create secret tls pod1-tls --key privkey.pem --cert fullchain.pem

Then, you can create your TLS Ingress resource : 

apiVersion: extensions/v1beta1  
kind: Ingress  
metadata:  
  name: pod1
  namespace: default
  annotations:
    nginx.org/ssl-services: "pod1"
    kubernetes.io/ingress.class: "nginx"
spec:  
  tls:
  - hosts:
    - pod1.example.com
    secretName: pod1-tls
  rules:
  - host: pod1.example.com
    http:
      paths:
      - path: /
        backend:
          serviceName: pod1
          servicePort: 443

As you see, The service pod1 is fully exposed with TLS.

IV- Use Calico for Network policies

Calico is a tool that enables Secure networking for the cloud native era. It is compatible with Kubernetes that allows many awesome options like :

  • Fine-grained networking policy
  • Routed networking between workers
  • BGP with core routers if want to totally disable NAT
  • IPv6 on pods (really soon)
  • Multiple IP Pools

And many other folks !

If you got a Kubernetes cluster with Calico, you can enable isolation in a namespace with this command : 

kubectl annotate ns my-namespace "net.beta.kubernetes.io/network-policy={\"ingress\":{\"isolation\":\"DefaultDeny\"}}"

For example, you can create a Nginx pod/service on my-namespace. Nobody can talk to him because the namespace is annoted with DefaultDeny.
If you want to allow the access to your Nginx, you need to define this rule with a NetworkPolicy like this : 

kind: NetworkPolicy  
apiVersion: extensions/v1beta1  
metadata:  
  name: access-nginx
  namespace: my-namespace
spec:  
  podSelector:
    matchLabels:
      run: nginx
  ingress:
    - from:
      - podSelector:
          matchLabels: {}

So, with that, you can clearly define in your cluster, which pod can speak to which other pod. If you want to install Calico in your Kubernetes cluster, please take a look to the documentation

V- GlusterFS for painless volumes

If you don't use a cloud providers who provide volume plugin for Kubernetes (AWS or Google Cloud), you will need to create your own external volume providers for your cluster.

GlusterFS is a tool that allows to share data (volumes) between two or more Linux servers and to use them in your Kubernetes cluster.

You can find a lot of posts about how to make a GlusterFS cluster. When you achieve this, here is how to use it in your Kubernetes installation :

First, you will need to install glusterfs-client on each worker.

After that, you need to get a Endpoint in the desired namespace : 

{
  "kind": "Endpoints",
  "apiVersion": "v1",
  "metadata": {
    "name": "glusterfs-cluster",
    "namespace": "default"
  },
  "subsets": [
    {
      "addresses": [
        {
          "ip": "10.240.0.100"
        }
      ],
      "ports": [
        {
          "port": 1
        }
      ]
    }
  ]
}

and a Service in the same namespace : 

{
  "kind": "Service",
  "apiVersion": "v1",
  "metadata": {
    "name": "glusterfs-cluster",
    "namespace": "default"
  },
  "spec": {
    "ports": [
      {"port": 1}
    ]
  }
}

Now, with theses resources, you can use the name glusterfs-cluster as a volume provider. Here is an example of a MariaDB pod : 

      containers:
      - image: mariadb:latest
        name: mariadb
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: DiThoshePh6oe45fezfz
        volumeMounts:
        - name: db-folder
          mountPath: /var/lib/mysql
      volumes:
        - name: db-folder
          glusterfs:
            endpoints: glusterfs-cluster
            path: gluster-volume-name
            readOnly: false

VI- Install k8s dashboard

The Kubernetes dashboard is a nice UI to see your cluster's status. It is quite easy to deploy in a new or existing cluster, just follow theses steps : 

kubectl create -f https://git.io/kube-dashboard

When all pods are created, you can access the dashboard using kubectl proxy: 

kubectl proxy  
http://127.0.0.1:8001/ui

VII- Use RBAC

RBAC (Roles based authentification control) is the perfect way to clearly define who can access to what in your cluster.
To enable RBAC in a Kubernetes cluster, you need to set this flag in the kube-apiserver configuration (Caution, it can break something in running cluster): 

  --authorization-mode=RBAC

When RBAC is enabled and you want to get admin users, you can put them in the system:masters group (highest admin level).

To create, for example, an user developer restricted to the dev namespaces, you will need to create a Role and a RoleBinding ressource : 

kind: Role  
apiVersion: rbac.authorization.k8s.io/v1beta1  
metadata:  
  namespace: dev
  name: role-developer
rules:  
- apiGroups: ["*"] # "" indicates the core API group
  resources: ["*"]
  verbs: ["*"]
---
kind: RoleBinding  
apiVersion: rbac.authorization.k8s.io/v1beta1  
metadata:  
  name: rolebinding-developer
  namespace: dev
subjects:  
- kind: User
  name: developer
  apiGroup: rbac.authorization.k8s.io
roleRef:  
  kind: Role
  name: role-developer
  apiGroup: rbac.authorization.k8s.io

RBAC allow you to clearly define your users authorization. To go more deeper in RBAC in Kubernetes I suggest you read the official documentation.

VIII- Follow your deployment logs

Kubetail is a small bash script that allow you to follow logs of every pod in a Kubernetes deployment. 

wget https://raw.githubusercontent.com/johanhaleby/kubetail/master/kubetail  
chmod +x kubetail && mv kubetail /usr/local/bin

Imagine you got a deployment called nginx and scaled to 10 pods, you can follow the 10 pods' logs with this command : 

kubetail nginx -n my-namespace

IX- Clean your cluster !

Continues deployment on top of a Kubernetes cluster is great but it creates a lot of old Docker images who, if you do nothing, grow and grow on your Workers file-system.

A good practice, to avoid Linux problem on Docker host, is to use a dedicated partition for the Docker folder (default /var/lib/docker).

A second point is to automate worker's cleanup (delete old images) with cron, configuration manager or a better approach, by Kubelet directly.

If you use Deployment on Kubernetes, be sure to use .spec.revisionHistoryLimit to limit ReplicaSets history on your cluster. If you don't do this, you can get quickly more than 100 old ReplicaSets.

That all for now !