Deploy Packages with Helm
Helm is the OLCF preferred package manager for Kubernetes. There are a variety of upstream applications that can be installed with helm, such as databases, web frontends, and monitoring tools. Helm has “packages” called “charts”, which can essentially be thought of as kubernetes object templates. You can pass in values which helm uses to fill in these templates, and create the objects (pods, deployments, services, etc)
Follow Helm Prerequisites for installing Helm.
One nice feature of helm is that it uses the underlying authentication credentials to kubernetes, so once you login with
oc login, the helm client will authenticate automatically.
By default, helm doesn’t have any chart repositories, so let’s add the upstream
helm repo add stable https://charts.helm.sh/stable
Now you can install helm charts with
helm install stable/<package_name>. You can think of this command as a parallel to running
yum install on a RHEL/CentOS-based system, or
apt install on a debian-based system.
Install MySQL with Helm
For an example, let’s install a basic mysql database, with a release named
You could simply run
helm install mysql stable/mysql, and an basic mysql deployment would be created with default values. However, we probably want to customize this deployment a bit. Let’s take a look at the documentation for the mysql helm chart.
Under the “Configuration” section, there is a large list of all the variables you can provide the chart, as well as their default values. Let’s say we want to customize our mysql resource utilization as well as using a block volume instead of the default NFS volume for persistent storage. We’ll also add a NodePort service in order to access our new database from outside the cluster.
There are two ways to set values for
Pass in individual values one-by-one with
Pass in a group of values within a file with
In this example, we’ll be using the latter method. Let’s create a file called
values.yaml with the following values:
You may need to adjust the persistence > size value down depending on the storage quotas set for your project. Your project quotas can be found at
https://quotas.CLUSTER.ccs.ornl.gov, where CLUSTER is replaced with the cluster you are running on (Marble/Onyx).
Now mysql can be installed with these values by running
helm install mysql stable/mysql --values values.yaml --namespace <project_name>
To install quickly with
--set instead of writing a values file, for example, if the default values are preferred except the persistent storage size and storageClass, this could be done by running
helm install mysql stable/mysql --set persistence.size="20Gi" --set persistence.storageClass="netapp-block". Note that you can pass multiple values by passing
--set multiple times.
To see all deployed helm charts in a namespace, along with their status, run
helm list --namespace <project_name>
If following the above example, this command will show the new mysql deployment, with
You can run
helm status <release_name> --namespace <project_name> in order to get information about the deployment. In this example, our release name is
mysql. Running this command for our
mysql installation will give us information on how to connect and authenticate to our newly created database.
The output of
helm status will differ from chart to chart, as this output is customizable by the chart itself. If the output has
kubectl commands to run,
kubectl can be replaced with
Finding New Charts
helm search hub will search the Helm Hub, which has a wide variety of publicly available charts. For example, if a wordpress installation is desired, you could run:
$ helm search hub wordpress
URL CHART VERSION APP VERSION DESCRIPTION
https://hub.helm.sh/charts/bitnami/wordpress 7.6.7 5.2.4 Web publishing platform for building blogs and ...
https://hub.helm.sh/charts/presslabs/wordpress-... v0.6.3 v0.6.3 Presslabs WordPress Operator Helm Chart
https://hub.helm.sh/charts/presslabs/wordpress-... v0.7.1 v0.7.1
Note that this searches much more than the
stable repo we added above, so you may need to add another repo with
helm repo add. Be sure to run
helm repo update before installing new charts, to make sure the charts are up to date.
You can also search only the repos that you have added to your local client with
helm search repo
It is also possible to write your own charts for helm, if you have an application that can be deployed to many namespaces or that could benefit from templating objects. How to write charts is outside the scope of this documentation, but the upstream docs are a great place to start.