Containers on Krkn

Package and Test the Image

Mon, 01 Jan 0001 00:00:00 +0000

Starting point: the plugin methods are implemented. Result: a locally tested image that clients can discover through its labels.

Build the custom Krkn base

Dockerfile.base overlays the local Python package on the published runtime:

FROM quay.io/krkn-chaos/krkn:latest

COPY --chown=krkn:krkn __init__.py \
 /home/krkn/kraken/krkn/scenario_plugins/dev_demo/__init__.py
COPY --chown=krkn:krkn dev_demo_scenario_plugin.py \
 /home/krkn/kraken/krkn/scenario_plugins/dev_demo/dev_demo_scenario_plugin.py

podman build \
 -f "$KRKN_DEV_PLUGIN_DIR/Dockerfile.base" \
 -t "$KRKN_BASE_IMAGE" \
 "$KRKN_DEV_PLUGIN_DIR"

Tip: Dockerfile path and build context are different

-f selects the Dockerfile; the final argument selects the directory available to its COPY instructions. -t assigns a local image name. Keeping both paths absolute makes this command work from any directory. Nothing is pushed to a registry at this stage.

This build context is the plugin repository. Using Krkn’s upstream container Dockerfile unchanged would clone Krkn from GitHub during the build and omit the local plugin. If you change the core engine or krkn-lib, build a runtime that includes those changes explicitly.

Scenario Image Contract

Mon, 01 Jan 0001 00:00:00 +0000

Krknctl and Krkn Operator discover scenario definitions from container image metadata. To add a custom scenario, publish an image with the expected labels and configure its registry in the client. You do not need to add the scenario to krknctl’s source code when the existing input types cover its parameters.

The packaging lab builds this contract without rebuilding krkn-hub. The definitions are implemented in krknctl’s input field parser and type validators.

Image labels

krknctl.is_a_scenario identifies scenario images when set to "true".
krknctl.title and krknctl.description describe the scenario.
krknctl.input_fields contains a JSON array of field descriptors.
krknctl.kubeconfig_path appears in the companion image as metadata. The clients used in this lab do not read it to configure the kubeconfig mount. Set the runtime mount path independently.
krknctl.privileged declares a privilege requirement. It is not an RBAC grant; actual permissions depend on the client, runtime, and target credentials.
krknctl.has_rollback describes rollback capability. Set it to match implemented behavior, not to indicate an intended future feature.

The base image can also supply global input labels such as krknctl.input_fields.global. Keep scenario-specific fields in the scenario label rather than copying every framework setting into it.

Publishing Through Krkn-hub

Mon, 01 Jan 0001 00:00:00 +0000

Krkn-hub maintains the community collection of packaged scenario images. Add your scenario there when you want it distributed through that collection. The custom scenario lab builds and publishes its own image directly, so it does not require changes to this repository.

Before contributing packaging, validate the Python plugin, configuration template, metadata, and executable startup script. Use the testing guide to cover success and failure paths.

Add the scenario package

Create a scenario directory in krkn-hub using a neighboring scenario as a reference. A package normally includes: