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kone Build Status

kone is a tool for building and deploying nodejs applications to Kubernetes.

kone is basically ko for Node.js.

Disclaimer: this is a prototype. Use at your own risk.


You need to have go. Then kone can be installed via:

go get

To update your installation:

go get -u

The kone Model

One of the goals of kone is to make containers invisible infrastructure. Simply replace image references in your Kubernetes yaml with the path for your Node.js application, and kone will handle containerizing and publishing that container image as needed.

For example, you might use the following in a Kubernetes Deployment resource:

apiVersion: apps/v1beta1
kind: Deployment
  name: hello-world
      foo: bar
  replicas: 1
        foo: bar
      - name: hello-world
        # This is the relative path for the Node.js application to containerize and run.
        image: ../my-node-app
        - containerPort: 8080

Determining supported node app

kone looks for package.json under the path specified in the YAML file. Relative paths are resolved from the YAML file location.

If found, kone checks:

  • the package name is set in package.json and use it as base image name
  • main.js exists, and use it as the docker entry point ENTRYPOINT ["node", "main.js"]

If one of the conditions is not met, kone skips the package.


Employing this convention enables kone to have effectively zero configuration and enable very fast development iteration.


kone has four commands, most of which build and publish images as part of their execution. By default, kone publishes images to a Docker Registry specified via KO_DOCKER_REPO.

However, these same commands can be directed to operate locally as well via the --local or -L command (or setting KO_DOCKER_REPO=ko.local). See the minikube section for more detail.

kone publish

kone publish simply builds and publishes images for each path passed as an argument. It prints the images' published digests after each image is published.

$ kone publish ./nodejs
2019/08/13 16:46:38 Using base for ./nodejs
2019/08/13 16:46:39 Publishing
2019/08/13 16:46:39 mounted blob: sha256:93f92d87eaa35181f944eee8bf9e240c09fd5b21b78ee865dd77676f5d646e9d
2019/08/13 16:46:39 mounted blob: sha256:a9d2af5037827579dd8de01460594e7ccaceff88a1381abf7e092f2f68329e31
2019/08/13 16:46:39 mounted blob: sha256:0a4690c5d889e116874bf45dc757b515565a3bd9b0f6c04054d62280bb4f4ecf
2019/08/13 16:46:39 mounted blob: sha256:68e3f078a91d377648dce9ab8f6a2fcf38164be1cc52eb1a6b4d9b633260cd79
2019/08/13 16:46:39 mounted blob: sha256:0cde646bed8c17ceb3ca87cdf65c9d25edfb803d0802fcac62f86b1e55d568e5
2019/08/13 16:46:39 existing blob: sha256:e4c49295e9e249983b0adee0ff7a643ee4248115d1245870b215d8ded74ef553
2019/08/13 16:46:40 pushed blob: sha256:5a0f660db6333b9bb7e46cf31a110741b97ab6c23c977e5e22b7f96cbbcf69a7
2019/08/13 16:46:40 digest: sha256:798e1d12b44c5cae81d8b36c913461299b19248b2ddd1fb206c882fef44c5939 size: 1242
2019/08/13 16:46:40 Published

kone resolve

kone resolve takes Kubernetes yaml files in the style of kubectl apply and (based on the model above) determines the set of paths to containerize, and publish.

The output of kone resolve is the concatenated yaml with paths replaced with published image digests. Following the example above, this would be:

# Command
export KO_DOCKER_REPO="<your-id>"
ko resolve -f deployment.yaml

# Output
apiVersion: apps/v1beta1
kind: Deployment
  name: hello-world
  replicas: 1
      - name: hello-world
        # This is the digest of the published image containing the go binary.
        - containerPort: 8080

kone resolve, kone apply, and kone create accept an optional --selector or -l flag, similar to kubectl, which can be used to filter the resources from the input Kubernetes YAMLs by their metadata.labels.

In the case of kone resolve, --selector will render only the resources that are selected by the provided selector.

See the documentation on Kubernetes selectors for more information on using label selectors.

kone apply

kone apply is intended to parallel kubectl apply, but acts on the same resolved output as kone resolve emits. It is expected that kone apply will act as the vehicle for rapid iteration during development. As changes are made to a particular application, you can run: kone apply -f unit.yaml to rapidly repush, and redeploy their changes.

kone apply will invoke kubectl apply under the hood, and therefore apply to whatever kubectl context is active.

kone delete

kone delete simply passes through to kubectl delete. It is exposed purely out of convenience for cleaning up resources created through kone apply.

kone version

kone version prints version of kone. For not released binaries it will print hash of latest commit in current git tree.

With minikube

You can use kone with minikube via a Docker Registry, but this involves publishing images only to pull them back down to your machine again. To avoid this, kone exposes --local or -L options to instead publish the images to the local machine's Docker daemon.

This would look something like:

# Use the minikube docker daemon.
eval $(minikube docker-env)

# Make sure minikube is the current kubectl context.
kubectl config use-context minikube

# Deploy to minikube w/o registry.
kone apply -L -f config/

# This is the same as above.
KO_DOCKER_REPO=ko.local kone apply -f config/

A caveat of this approach is that it will not work if your container is configured with imagePullPolicy: Always because despite having the image locally, a pull is performed to ensure we have the latest version, it still exists, and that access hasn't been revoked. A workaround for this is to use imagePullPolicy: IfNotPresent, which should work well with kone in all contexts.

Images will appear in the Docker daemon as ko.local/

Configuration via .ko.yaml

While ko aims to have zero configuration, there are certain scenarios where you will want to override kone's default behavior. This is done via .ko.yaml.

.ko.yaml is put into the directory from which kone will be invoked. One can override the directory with the KO_CONFIG_PATH environment variable.

If neither is present, then kone will rely on its default behaviors.

Overriding the default base image

By default, kone makes use of as the base image for containers. There are a wide array of scenarios in which overriding this makes sense, for example:

  1. Pinning to a particular digest of this image for repeatable builds,
  2. Replacing this streamlined base image with another with better debugging tools (e.g. a shell, like

The default base image kone uses can be changed by simply adding the following line to .ko.yaml:


Why isn't KO_DOCKER_REPO part of .ko.yaml?

Once introduced to .ko.yaml, you may find yourself wondering: Why does it not hold the value of $KO_DOCKER_REPO?

The answer is that .ko.yaml is expected to sit in the root of a repository, and get checked in and versioned alongside your source code. This also means that the configured values will be shared across developers on a project, which for KO_DOCKER_REPO is actually undesirable because each developer is (likely) using their own docker repository and cluster.

Including static assets

kone includes all assets in your node root directory.

Enable Autocompletion

To generate an bash completion script, you can run:

kone completion

To use the completion script, you can copy the script in your bash_completion directory (e.g. /usr/local/etc/bash_completion.d/):

kone completion > /usr/local/etc/bash_completion.d/kone

or source it in your shell by running:

source <(kone completion)

Relevance to Release Management

kone is also useful for helping manage releases. For example, if your project periodically releases a set of images and configuration to launch those images on a Kubernetes cluster, release binaries may be published and the configuration generated via:

export KO_DOCKER_REPO="<your-id>"
kone resolve -f config/ > release.yaml

This will publish all of the components as container images to<your-id>/... and create a release.yaml file containing all of the configuration for your application with inlined image references.

This resulting configuration may then be installed onto Kubernetes clusters via:

kubectl apply -f release.yaml


This work 99% ko.

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