Kubernetes packaging and deploying¶

Helm¶

Helm is the best way to find, share and use software built for Kubernetes
Helm is a package manager for Kubernetes
It helps you to manage Kubernetes applications
Helm is maintainted by the CNCF - The Cloud Native Computing Foundation (together with Kubernetes, fluentd, linkderd, and others)
- Is’s now maintained in collaboration with Microsoft, Google, Bitnami and the helm contributor community.
To start using helm, you first need to download the helm client (https://github.com/helm/helm/releases/tag/v2.11.0)
You need to run helm init to initialize helm on the kubernetes cluster
- This will install Tiller
- If you have RBAC installed (recent clusters have it enabled now by default), you’ll also need to add a ServiceAccount and RBAC rules
After this, helm is ready to use, and you can start installing charts

Charts¶

Helm uses a packaging format called charts
- A chart is a collection of files that describe a set of Kubernetes resources
- A single chart can deploy an app, a piece of software or a database for example
- It can have dependencies, e.g. to install wordpress chart, you need a mysql chart
- You can write your own chart to deploy your application on Kubernetes using helm
Charts use templates that are typically developed by a package maintainer
They will generate yaml files that Kubernetes understands
You can think of templates as dynamic yaml files, which can contain logic and variables
This is an example of a template within a chart:

apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Release.Name }}-configmap
data:
  myvalue: "Hello World"
  drink: {{ .Values.favoriteDrink }}

The favoriteDrink value can then be overridden by the user when running helm install

Helm service account¶

apiVersion: v1
kind: ServiceAccount
metadata:
  name: tiller
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: tiller
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subject:
  - kind: ServiceAccount
    name: tiller
    namespace: kube-system

Common commands¶

Command	Description
helm init	Install tiller on the cluster
helm reset	Remove tiller from the cluster
helm install	Install a helm chart
helm search	search for a chart
helm list	list releases (installed charts)
helm upgrade	upgrade a release
helm rollback	rollback a release to a previous version

Create your own charts¶

You can create helm charts to deploy your own apps
It’s the recommended way to deploy your applications on Kubernetes
- Packaging the app allows you to deploy the app in 1 command (instead of using kubectl create / apply)
- Helm allows for upgrades and rollbacks
- Your helm chart is version controlled
To create the files necessary for a new chart, you can run the command:

helm create <mychart>

This will create a directory structure <mychart> and some files and subdirectories.