Carvel

Carvel is a set of single-purpose Kubernetes tools; its in-cluster engine, kapp-controller, fetches, templates, and deploys application configuration through a declarative pipeline.

• Category: App Definition & GitOps
• CNCF maturity: Sandbox
• Language: Go
• License: Apache-2.0
• Repository: carvel-dev/kapp-controller
• Documented at commit: be1faef (v0.60.3)

What it is

Carvel is not one program. It is a family of small command-line tools, each doing one job: ytt templates YAML, kbld resolves image references, imgpkg packages configuration as Open Container Initiative (OCI) images, vendir vendors remote sources, and kapp applies a set of resources to a cluster as one unit. The tools are meant to be composed, the way UNIX commands are composed with pipes.

This deep-dive covers kapp-controller, the in-cluster engine that ties those tools together. It is a Kubernetes controller built on controller-runtime. It watches custom resources (CRs), starting with App, PackageInstall, and PackageRepository, and for each App it runs a three-stage pipeline: fetch the configuration, template it, then deploy it. Each stage shells out to one of the Carvel command-line tools.

kapp-controller sits where GitOps engines and package managers sit. An App resource declares where its configuration comes from, how to render it, and how to apply it. kapp-controller reconciles that declaration against the cluster on a timer and records the result of each stage in the resource status.

When to use it

• You want declarative, continuous reconciliation of application configuration from git, Helm charts, or OCI bundles, with drift correction handled by kapp.
• You want to distribute software as versioned packages that cluster operators install with a PackageInstall, similar to a package manager backed by an OCI registry.
• You prefer composing focused tools over one monolithic templating-and-deploy binary.
• It is a weaker fit if you only need a one-shot client-side apply, or if your team is already standardised on a single GitOps controller and does not want a second reconciler in the cluster.

In this deep-dive

• History: origin, milestones, and why it exists.
• Architecture: components and how a reconcile flows.
• Adoption & Ecosystem: who runs it and what surrounds it.
• Internals: the code paths that matter, read from source.
• Getting Started: install and a first working setup.

Sources

1. carvel-dev/kapp-controller (main implementation), accessed 2026-06-26.
2. carvel-dev/carvel (umbrella and community), accessed 2026-06-26.
3. Introduction to Carvel, accessed 2026-06-26.
4. Carvel Sets Sail for the CNCF Sandbox (VMware OSS), accessed 2026-06-26.
5. Project Carvel has joined the CNCF, accessed 2026-06-26.
6. CNCF project page: Carvel, accessed 2026-06-26.
7. kapp-controller documentation, accessed 2026-06-26.
8. Comparing Kubernetes deployment tools (NETWAYS), accessed 2026-06-26.
9. kapp-controller releases (v0.60.3 assets), accessed 2026-06-26.