Helm, the package manager for Kubernetes, is a useful tool for: installing, upgrading and managing applications on a Kubernetes cluster. Helm packages are called charts. We will be installing and managing JupyterHub on our Kubernetes cluster using a Helm chart.
Charts are abstractions describing how to install packages onto a Kubernetes cluster. When a chart is deployed, it works as a templating engine to populate multiple yaml files for package dependencies with the required variables, and then runs kubectl apply to apply the configuration to the resource and install the package.
yaml
kubectl apply
Helm has two parts: a client (helm) and a server (tiller). Tiller runs inside of your Kubernetes cluster as a pod in the kube-system namespace. Tiller manages both, the releases (installations) and revisions (versions) of charts deployed on the cluster. When you run helm commands, your local Helm client sends instructions to tiller in the cluster that in turn make the requested changes.
helm
tiller
Note
These instructions are for Helm 2. Helm 3 includes several major breaking changes and is not yet officially supported, but preliminary instructions are available for testing.
While several methods to install Helm exists, the simplest way to install Helm is to run Helm’s installer script in a terminal:
curl https://raw.githubusercontent.com/kubernetes/helm/master/scripts/get | bash
After installing helm on your machine, initialize Helm on your Kubernetes cluster:
Set up a ServiceAccount for use by tiller.
kubectl --namespace kube-system create serviceaccount tiller
Give the ServiceAccount full permissions to manage the cluster.
ServiceAccount
If you know your kubernetes cluster does not have RBAC enabled, you must skip this step. Most users can ignore this note.
kubectl create clusterrolebinding tiller --clusterrole cluster-admin --serviceaccount=kube-system:tiller
See our RBAC documentation for more information.
Initialize helm and tiller.
helm init --service-account tiller --history-max 100 --wait
This command only needs to run once per Kubernetes cluster, it will create a tiller deployment in the kube-system namespace and setup your local helm client. This command installs and configures the tiller part of Helm (the whole project, not the CLI) on the remote kubernetes cluster. Later when you want to deploy changes with helm (the local CLI), it will talk to tiller and tell it what to do. tiller then executes these instructions from within the cluster. We limit the history to 100 previous installs as very long histories slow down helm commands a lot.
If you wish to install helm on another computer, you won’t need to setup tiller again but you still need to initialize helm:
helm init --client-only
Ensure that tiller is secure from access inside the cluster:
kubectl patch deployment tiller-deploy --namespace=kube-system --type=json --patch='[{"op": "add", "path": "/spec/template/spec/containers/0/command", "value": ["/tiller", "--listen=localhost:44134"]}]'
tiller s port is exposed in the cluster without authentication and if you probe this port directly (i.e. by bypassing helm) then tiller s permissions can be exploited. This step forces tiller to listen to commands from localhost (i.e. helm) only so that e.g. other pods inside the cluster cannot ask tiller to install a new chart granting them arbitrary, elevated RBAC privileges and exploit them. More details here.
You can verify that you have the correct version and that it installed properly by running:
helm version
It should in less then a minute, when tiller on the cluster is ready, be able to provide output like below. Make sure you have at least version 2.11.0 and that the client (helm) and server version (tiller) is matching!
Client: &version.Version{SemVer:"v2.11.0", GitCommit:"2e55dbe1fdb5fdb96b75ff144a339489417b146b", GitTreeState:"clean"} Server: &version.Version{SemVer:"v2.11.0", GitCommit:"2e55dbe1fdb5fdb96b75ff144a339489417b146b", GitTreeState:"clean"}
Congratulations, Helm is now set up! Let’s continue with Setting up JupyterHub!