What is Helm and Why is it Used?

Helm is a powerful tool used to manage Kubernetes applications, simplifying the process of deploying, configuring, and managing applications within Kubernetes clusters. Often referred to as the "package manager for Kubernetes," Helm allows developers and system administrators to easily install and manage applications in Kubernetes clusters, enabling both speed and efficiency in operations. But what exactly is Helm? Why is it so important in the world of Kubernetes? Let’s dive deep into understanding Helm and how it fits into the Kubernetes ecosystem.

Understanding Kubernetes and the Need for Helm

To understand the role of Helm, it’s essential to first grasp what Kubernetes is and the challenges it introduces for application management.

Kubernetes, often abbreviated as K8s, is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. In simpler terms, it’s a tool used to manage containers (such as Docker containers) at scale. Kubernetes has grown in popularity due to its powerful features that support multi-cloud, hybrid-cloud, and on-premises environments. It is often used in enterprise settings where containerized applications need to be deployed and scaled across different infrastructures.

However, managing Kubernetes can be complex due to the dynamic nature of the system and the need to configure many aspects, such as deployments, replicas, services, and configurations. This is where Helm comes in.

What is Helm?

Helm is a package manager for Kubernetes applications. In traditional package managers like apt for Ubuntu and yum for Red Hat Enterprise Linux (RHEL), users can easily install, upgrade, and manage software packages. Helm does the same thing, but specifically for Kubernetes applications. Helm simplifies the deployment process by packaging complex Kubernetes configurations into reusable charts.

A Helm Chart is a collection of Kubernetes resources (such as deployment, services, ingress, config maps, secrets, etc.) that are packaged together in a way that makes it easy to deploy and manage these resources. These charts can be versioned, shared, and reused across multiple Kubernetes clusters, making it easier to maintain infrastructure as code.

Helm's Key Components

1. Helm Chart: A Helm chart is a pre-configured Kubernetes application. Charts are a collection of files that describe a related set of Kubernetes resources. Charts allow you to easily install, configure, and deploy Kubernetes applications. They contain templates, default values, and configuration files to ensure that the resources created by Helm are ready to run in a Kubernetes cluster.

2. Helm CLI (Command Line Interface): The Helm CLI is the tool that users interact with to manage Helm charts. It provides commands for installing, upgrading, and managing applications, such as helm install, helm upgrade, and helm uninstall.

3. Helm Repository: A Helm repository is where Helm charts are stored. Repositories can be public or private. When you use Helm to install a chart, it fetches the chart from a repository. Popular repositories include Helm Hub and Bitnami, which provide a vast selection of pre-built charts for common applications.

4. Helm Release: A release is an instance of a Helm chart running in a Kubernetes cluster. For example, if you use Helm to install a chart for a database, the instance running in your Kubernetes cluster is a release.

5. Values: Helm charts allow for configuration of various parameters and values that can be customized at deployment time. These values can be overridden by the user through the values.yaml file or by passing configuration flags when running the helm install command. This makes Helm highly configurable for different environments.

Why Use Helm?

Helm solves a number of challenges associated with managing Kubernetes applications. Here are some of the key reasons why Helm is essential:

1. Simplified Deployment and Configuration

One of the major challenges in Kubernetes is the complexity of deploying and managing applications. Kubernetes has many configuration files that must be carefully structured to ensure proper functionality. With Helm, developers can use pre-configured charts that automate the creation of necessary Kubernetes resources. Helm takes care of the underlying complexity by managing everything in a Kubernetes-friendly way.

For example, when installing a complex application like a database or messaging queue, the chart provided by Helm includes all the necessary Kubernetes resources like deployments, services, config maps, and secrets. With a simple helm install command, you can deploy the entire application, including all its components.

2. Version Control and Rollback

Helm provides built-in version control for your Kubernetes applications. When you deploy a chart, Helm keeps track of the version of the chart and its configuration. This allows for easy upgrades and rollbacks.

For instance, if an upgrade to an application introduces a bug or unexpected behavior, you can use Helm to roll back to a previous version of the release. This is invaluable in production environments where downtime or failures can be costly.

The command helm rollback <release-name> <revision-number> makes it easy to go back to a previous stable release.

3. Reusability and Sharing

Helm charts can be shared with others, making it easy for developers to reuse commonly used applications. Whether you’re deploying a custom-built application or leveraging an open-source chart, you can store and share your Helm charts in a repository.

Helm charts are also reusable across multiple Kubernetes clusters. If you’ve created a set of Helm charts for a specific application, you can easily replicate that application in any Kubernetes environment by simply pointing Helm to the chart repository.

4. Declarative and Scalable Infrastructure

Helm works with Kubernetes’ declarative model, meaning you declare the desired state of your infrastructure, and Kubernetes works to achieve that state. Helm enhances this declarative approach by managing application-level resources and configurations, enabling you to treat infrastructure as code. Helm charts ensure that all resources are correctly defined and consistently applied across environments.

5. Helm Supports Customization

Helm allows for customization at the time of installation. Developers can use values.yaml to specify configuration options, or pass custom values directly via the command line. This makes Helm extremely flexible, as it can be tailored to meet the needs of different environments or use cases.

For example, you can configure a chart to deploy an NGINX server with specific resource limits or specify the number of replicas you want for your application’s deployment. All of these can be done easily through Helm values.

6. Helm's Ecosystem

The Helm ecosystem has become a thriving community, with many open-source charts available in repositories like Helm Hub and Bitnami. These repositories provide pre-packaged Helm charts for popular applications like WordPress, MySQL, PostgreSQL, Redis, and many more. This allows teams to quickly get started with common software and best practices without having to write Kubernetes manifests from scratch.

How Helm Differs from Traditional Package Managers (APT, YUM)

In traditional package managers like APT (Advanced Package Tool) for Ubuntu and YUM (Yellowdog Updater, Modified) for RHEL (Red Hat Enterprise Linux), users install packages from repositories to manage software dependencies, updates, and installations. Helm works similarly but specifically within the Kubernetes ecosystem, targeting Kubernetes applications and managing them as packages (or charts).

Helm vs. APT (Ubuntu)

• APT: APT is the default package manager for Debian-based distributions like Ubuntu. It allows users to install, update, and remove software packages from repositories. These packages are typically precompiled binaries that contain the application and its dependencies.

• Helm: Helm, on the other hand, deals with managing Kubernetes applications, not just software binaries. It installs applications that consist of several Kubernetes objects (like deployments, services, config maps, etc.), and it manages all of these resources as a unit.

In summary, while APT manages software packages for the underlying operating system, Helm manages complex Kubernetes applications and resources, abstracting much of the complexity involved in deploying and maintaining them.

Helm vs. YUM (RHEL)

• YUM: YUM is the default package manager for RHEL and CentOS, and it’s used to install, update, and manage software packages from repositories, similar to APT.

• Helm: Helm similarly manages application packages for Kubernetes, but unlike YUM, it focuses on the deployment and management of applications within Kubernetes clusters.

While YUM is used for managing packages on physical or virtual machines, Helm is a tool for managing applications within the Kubernetes ecosystem.

How to Install Helm

Installing Helm is a straightforward process. Here’s how to install Helm on Ubuntu (using APT) and RHEL (using YUM):

For Ubuntu (APT)

1. Install the required dependencies:

   sudo apt-get install apt-transport-https --yes
   

2. Add the Helm repository:

   curl https://baltocdn.com/helm/signing.asc | sudo apt-key add -
   

3. Add the Helm repo to your sources list:

   sudo apt-get install software-properties-common
   sudo apt-add-repository "deb https://baltocdn.com/helm/stable/debian/ all main"
   

4. Update the package list:

   sudo apt-get update
   

5. Install Helm:

   sudo apt-get install helm
   

For RHEL (YUM)

1. Add the Helm repository:

   curl https://baltocdn.com/helm/signing.asc | sudo tee /etc/yum.repos.d/helm.repo
   

2. Install Helm:

   sudo yum install helm
   

Helm has become an indispensable tool for managing Kubernetes applications. It simplifies the process of deploying, upgrading, and managing complex applications in Kubernetes clusters by using pre-configured Helm charts. Helm makes Kubernetes applications more accessible, easier to manage, and quicker to deploy, all while offering powerful features like version control, rollback, and customizability.

Whether you're deploying a simple application or managing a large-scale microservices architecture, Helm’s ability to package, distribute, and manage Kubernetes resources with ease makes it a must-have tool for any Kubernetes user.

If you're using Kubernetes in your development or production environments, Helm will save you time, reduce errors, and streamline your workflow. It is, without a doubt, a powerful addition to any Kubernetes toolkit.