Introduction to Helm¶

Helm is the package manager for Kubernetes.

This means you can package your kubernetes YAML manifest files and distribute them through public or private helm repositories.

You know that:

apt is a package manager for Debian, and Debian-based Linux distributions, yum
homebrew is a package manager for Apple's operating system, macOS

Helm does the similar job but for Kubernetes packages.

A Chart is a Helm package. Think of it like the Kubernetes equivalent of a homebrew formula, an apt dpkg, or a yum RPM file.

Example Use Case of Helm Chart¶

Consider you need to deploy prometheus in your EKS cluster. Prometheus is a stateful application and has a lot of components.

Method 1: Write YAML manifest files for all the componets¶

This is going to be a cumbersome task since you need to look for the manifest files for all components on the internet. You may need to edit all the manifest to meet your needs. For example you might want to change namespace in all the manifest.

What about updates? What if something changed in prometheus architecture? Incorporating those changes in your manifest is going to be a nightmare.

Method 2: Use Helm Chart¶

What if someone has already packaged all the required YAML manifests together and published it as a package (chart in helm) in some repository?

This will make your life easier. You just need to install the chart and you are good to go.

You can also replace values easily. For example, if you want to deploy the prometheus resources in a particular namesapce, you can do that just by setting the required placeholder with the value you desire. (Remember set parameter?)

Install Helm CLI¶

See the installation guide to instlal Helm CLI on your operating system.

Verify if helm is installed:

helm version

The output will be similar to the below:

version.BuildInfo{Version:"v3.11.1", GitCommit:"293b50c65d4d56187cd4e2f390f0ada46b4c4737", GitTreeState:"clean", GoVersion:"go1.18.10"}

Now, let's see how you can work with Helm CLI to install charts in your kubernetes cluster.

Prerequisites¶

You must have the following in place before you can start working with Helm:

A Kubernetes Cluster
A local configured copy of kubectl

Initialize a Helm Chart Repository¶

Once you have Helm CLI installed, you can add a chart repository. A chart repository is a server that houses packaged charts.

For example, Helm hub is the official public repository for Helm Charts.

Let's add bitnami helm chart repository as follows:

helm repo add bitnami https://charts.bitnami.com/bitnami

You can see which repositories are configured using the following command:

helm repo list

Now that you have added the bitnami repo, you can search the charts that are published in that repository using helm search command as follows:

# Command template
helm search repo <repo-name>

# Example
helm search repo bitnami

It will output a list of Helm charts available in the bitnami Helm chart repository, along with details such as chart name, version, description, and other relevant information.

Install a Chart¶

Now that we have added the repository. We can install charts from that repository.

Update the repo to make sure we get the latest list of charts:
```
helm repo update
```

Install the chart:

# Command template to install a chart
helm install <name> <chart>

# Example
helm install mysql bitnami/mysql

The charts will be installed in the default namespace. You can use the --namespace or -n to install it in a particular namespace.

# Create namespace mysql
kubectl create namespace mysql

# Install mysql in mysql namespace
helm install mysql bitnami/mysql -n mysql

You can get a basic idea of the features of this MySQL chart by running the following command:

helm show chart bitnami/mysql -n <namespace>

Helm does not wait until all of the resources are running before it exits. Many charts require Docker images that are over 600M in size, and may take a long time to install into the cluster.

To keep track of a release's state, or to re-read configuration information, you can use helm status command as follows:

helm status mysql -n <namespace>

When installing Helm charts with the helm install command, the --set argument allows you to define values used in a chart’s templates.

For example, when installing prometheus using helm you can set the values as per your need as follows:

# Helm install with set argument
helm install prometheus prometheus-community/prometheus --namespace prometheus --set server.persistentVolume.size=20Gi --set server.retention=15d

Alternatively, you can also set values using a custom YAML file:

helm install prometheus prometheus-community/prometheus --namespace prometheus --values my-values.yml

Yourmy-values.yml may look like the below:

server:
    persistentVolume:
        size: 20Gi
    retention: 15d

Show Default values.yml for a Given Chart¶

You can use the following commmand to view the default values for a chart:

# Command template
helm show values <chart>

# Example
helm show values prometheus-community/prometheus

Helm Releases¶

The helm list (or helm ls) command will show you a list of all deployed releases:

# Command template
helm list -n <namespace>

# List all deployed releases in default namespace
helm list

# List all deployed releases in prometheus namespace
helm list -n prometheus

Uninstall a Release¶

Use the helm uninstall command to uninstall a release:

# Command template
helm uninstall <name> -n namespace

# Example
helm uninstall mysql