App CR High Level Overview

Overview ¶

kapp-controller provides a declarative way to install, manage, and upgrade applications on a Kubernetes cluster using the App CRD. Get started by installing the latest release of kapp-controller.

App ¶

An App is a set of Kubernetes resources. These resources could span any number of namespaces or could be cluster-wide (e.g. CRDs). An App is represented in kapp-controller using a App CR.

The App CR comprises of three main sections:

• spec.fetch – declare source for fetching configuration and OCI images
• spec.template – declare templating tool and values
• spec.deploy – declare deployment tool and any deploy specific configuration

Full App CR spec can be found here.

spec.fetch ¶

App CR supports multiple source for fetching configuration and OCI images to give developers flexibility.

• inline: specify one or more files within resource
• imgpkgBundle: download imgpkg bundle from registry (available in v0.17.0+)
• image: download Docker image from registry
• http: download file at URL
• git: clone Git repository
• helmChart: fetch Helm chart from Helm repository

For each fetch source, App CR supports specifying Secret resources that will be used for authenticating with the source. kapp-controller does not check for type value of Secret resource.

image and imgpkgBundle authentication ¶

Allowed secret keys:

• username and password
• token: Alternative to username/password authentication

Also supports dockerconfigjson secret type (v0.19.0+)

git authentication ¶

Allowed secret keys:

• ssh-privatekey: PEM-encoded key that will be provided to SSH
• ssh-knownhosts: Optional, set of known hosts allowed to connect (if not specified, all hosts are allowed)
• username and password: Alternative to private key authentication

http and helmChart authentication ¶

Allowed secret keys:

• username and password

spec.template ¶

App CR supports multiple templating, overlaying, and data transformation tools to give developers flexibility.

• helmTemplate: uses helm template command to render chart
• ytt: uses ytt to rended templates
• kbld: uses kbld to resolve image URLs to include digests
• kustomize: (not implemented yet) uses kustomize to render configuration
• jsonnnet: (not implemented yet) renders jsonnet files
• sops: uses sops to decrypt secrets. More details. Available in v0.11.0+.

spec.deploy ¶

App CR uses Carvel’s kapp CLI to deploy.

• kapp: uses kapp to deploy resources