What are Rancher catalogs and how do you deploy applications from the app marketplace?

Think of Rancher catalogs as an app store for your Kubernetes clusters. Just as you browse a phone's app store, find an application, configure a few settings, and tap 'Install,' Rancher catalogs let you browse Helm charts, customize values, and deploy complex applications without manually writing or managing Helm templates.

Rancher catalogs are repositories of Helm charts that are integrated into the Rancher UI as an app marketplace. Rancher ships with several built-in catalogs: the official Rancher charts (maintained by the Rancher team), the Partner charts (from certified technology partners), and community-contributed charts. You can also add custom catalog repositories by pointing Rancher to any Helm chart repository URL or a Git repository containing charts. Once a catalog is added, its charts appear in the Rancher Apps section, where you can browse, search, and install them.

When you install an application from the catalog, Rancher presents a form based on the chart's values.yaml file. You configure options like replica counts, storage sizes, ingress hostnames, and resource limits through this form. Behind the scenes, Rancher uses Helm to render the templates with your custom values and applies the resulting Kubernetes manifests to the cluster. The installed application appears in the Apps section with version tracking, upgrade history, and the ability to modify values and re-deploy. Upgrades are handled through the same interface: when a new chart version is available, Rancher shows an upgrade indicator.

In production, catalogs are essential for standardizing deployments across clusters. A platform engineering team creates a custom catalog repository containing approved Helm charts for services like PostgreSQL, Redis, RabbitMQ, and the company's own microservices. They configure Rancher to use this catalog across all managed clusters, ensuring that every team deploys the same vetted versions with the same security configurations. For example, the order-service team needs a Redis cache. Instead of writing their own Redis deployment manifests, they install Redis from the approved catalog, which already includes security hardening, resource limits, and backup sidecar containers defined by the platform team.

A common beginner mistake is confusing catalogs with Rancher Fleet (GitOps). Catalogs are interactive, click-to-install deployments primarily used for infrastructure components and shared services. Fleet, on the other hand, is a GitOps engine for continuously deploying application workloads from Git repositories. In practice, teams use catalogs for platform-level infrastructure (monitoring, logging, ingress controllers) and Fleet or another GitOps tool for application workloads (payments-api, user-auth-service).