Kubernetes: From Zero to Hero (Part 10) - Helm
Tags: beginners, kubernetes, devops, tutorial
Published: 2022-12-30 12:15:10

## Introduction to Helm and its role in Kubernetes

Helm is an open source package manager for Kubernetes that simplifies the deployment and management of applications on the Kubernetes platform. It helps you define, install, and upgrade complex Kubernetes applications, and it provides a way to package all of the resources required for an application into a single, easy-to-use package called a chart.

Imagine that you have a web application that you want to deploy to a Kubernetes cluster. Without Helm, you would have to manually create all of the required Kubernetes resources, such as pods, services, and deployment objects, and then use the kubectl command-line tool to deploy them to your cluster. This process can be time-consuming and error-prone, especially if you have multiple microservices or dependencies that need to be deployed.

With Helm, you can create a chart that defines all of the resources required for your application, and then use the Helm CLI to deploy the chart to your cluster with a single command. This saves time and reduces the risk of mistakes, making it easier to manage and update your applications over time.

## Installing Helm

To use Helm, you will need to have a Kubernetes cluster set up and the kubectl command-line tool installed on your local machine. If you don't already have a cluster, you can follow the instructions on the Kubernetes website to set one up.

Once you have a cluster and kubectl installed, you can install Helm by downloading the latest release from the Helm website and following the installation instructions. On macOS or Linux, you can use the following command to install Helm:

```bash
curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash
```
This will download the Helm binary and add it to your PATH, so you can use the Helm CLI from any directory.

If you want to install Helm on a Kubernetes cluster, you can use the Helm CLI to install the Helm server-side component, Tiller, on the cluster. To do this, run the following command:

```bash
helm init
```
This will install Tiller on the default namespace of your cluster. If you want to install Tiller on a different namespace, you can use the --namespace flag.

## Using Helm

Once Helm is installed, you can use the Helm CLI to search for, install, and manage charts.

To search for charts in the official Helm repository, use the search command:

```bash
helm search repo <chart-name>
```
This will return a list of charts that match the search term. You can then use the install command to install a chart from the repository:

```bash
helm install <chart-name>
```
This will create all of the required resources for the chart on your cluster. You can use the get command to list the releases (i.e. deployments) of a chart:

```bash
helm get releases
```
To update a release, you can use the upgrade command:

```bash
helm upgrade <release-name> <chart-name>
```
This will update the resources for the release to the latest version of the chart.

You can also create your own charts by using the create command:

```bash
helm create <chart-name>
```
This will create a starter chart with the necessary files and directories. You can then modify the chart files to define the resources that you want to deploy and customize the behavior of the chart.

To view the resources that are defined in a chart, you can use the helm show command:

```bash
helm show chart <chart-name>
```
Upgrading and rolling back deployments:
To upgrade a deployment to the latest version of a chart, use the helm upgrade command:

```bash
helm upgrade <release-name> <chart-name>
```
To roll back a deployment to a previous version, use the helm rollback command:

```bash
$ helm rollback <release-name> <revision>
```

## Best practices for using Helm in a production environment

When using Helm in a production environment, it's important to follow some best practices to ensure the stability and reliability of your deployments. Here are a few tips:

- Use version control for your charts to track changes and roll back if necessary
- Test your charts thoroughly before deploying them to production
- Use Helm's built-in security features, such as chart signing and repository authentication, to protect your deployments
- Use Helm's dependency management features to ensure that all required charts are installed and upgraded in the correct order
- Use Helm's release management features, such as the ability to roll back to previous versions, to recover from failures or errors in your deployments.

## Advanced Helm features

In addition to the basic Helm commands described above, there are several advanced features that can be useful in a production environment.

- **Using Helm with continuous integration/continuous deployment (CI/CD) pipelines:** Helm can be used in combination with a CI/CD tool, such as Jenkins or CircleCI, to automate the deployment of applications to a Kubernetes cluster. For example, you could set up a pipeline that automatically builds and deploys your application whenever you push changes to a Git repository. To use Helm with a CI/CD tool, you can set up a script that uses the Helm CLI to install or upgrade charts as part of the deployment process.
- **Customizing chart values and using templates for deployment configuration:** Chart values are variables that can be used to customize the behavior of a chart when it is installed. For example, you might use chart values to specify the number of replicas for a deployment or the image tag for a container. Helm charts can use templates to define how these values should be applied to the resources in the chart. This allows you to define reusable templates that can be used across multiple charts, and it makes it easier to manage and maintain your deployments over time.
Here's an example of how to use chart values and templates in a chart:

```yaml
# values.yaml
replicaCount: 3
image:
  repository: nginx
  tag: latest

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
      - name: {{ .Release.Name }}
        image: {{ .Values.image.repository }}:{{ .Values.image.tag }}
```
In this example, the replicaCount and image values can be customized when the chart is installed using the --set flag:

```bash
helm install <chart-name> --set replicaCount=5,image.tag=stable
```
Using Helm hooks to execute tasks before or after chart installation or upgrade:
Helm provides the ability to use hooks to execute tasks before or after chart installation or upgrade. Hooks are defined in the chart and can be used to perform tasks such as creating a database, migrating data, or sending notifications. This can be especially useful when deploying complex applications that have dependencies on other services or resources.

Here's an example of how to use a hook in a chart:

```yaml
# hooks/post-install.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: {{ .Release.Name }}-post-install
spec:
  template:
    spec:
      containers:
      - name: post-install
        image: busybox
        command: ["echo", "Post-install hook ran"]
  restartPolicy: Never
```
In this example, the hook is a Kubernetes Job that runs a simple command after the chart is installed.

Using Helm to manage dependencies between charts:
Helm provides a way to manage dependencies between charts. This can be useful when you have multiple charts that are used together to form a complete application. For example, if you have a chart for a web server and a chart for a database, you can use the dependencies feature to ensure that the database chart is installed before.

In conclusion, Helm is a powerful tool for managing applications on Kubernetes. It simplifies the deployment and management of complex applications by providing a way to package all of the resources needed for an application into a single chart. Helm also offers advanced features such as the ability to use templates to customize deployment configurations, use hooks to execute tasks before or after chart installation or upgrade, and manage dependencies between charts.

Some of the main benefits and features of Helm include:

- Simplified deployment and management of complex applications on Kubernetes
- Ability to search for and install charts from repositories
- Ability to create and manage custom charts
- Ability to upgrade and roll back deployments
- Advanced features such as chart values, templates, hooks, and dependency management

If you are using Kubernetes and want an easier way to manage your applications, Helm is a great tool to consider. To learn more about Helm and how to use it, you can check out the Helm documentation (https://helm.sh/docs/) and the Kubernetes documentation. There are also many online resources and tutorials available for learning more about Helm and Kubernetes.

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