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https://github.com/rancher/k3c

Lightweight local container engine for container development
https://github.com/rancher/k3c

docker kubernetes

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Lightweight local container engine for container development

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k3c - Classic Docker (Build) for a Kubernetes world

===========================================



***STATUS: EXPERIMENT - Let us know what you think***



***NOTE: the original experiment started on `master` while the next-gen work will be on `main`***



`k3c` brings the Classic ™ Docker images manipulation UX to your

`k3s` development workflow. It is designed to enable the rapid feedback

when developing and testing local container images in `k3s` and `rke2`.

Currently `k3s`, the [lightweight Kubernetes distribution](https://github.com/k3s-io/k3s),

provides a great solution for Kubernetes from dev to production.  While

`k3s` satisifies the Kubernetes runtime needs, one still needs to run

`docker` (or a docker-like tool) to actually develop and build the container

images.  `k3c` is intended to replace `docker` for just the functionality

needed for building and manipulating images in the Kubernetes ecosystem.



## A familiar UX



There really is nothing better than the classic Docker UX of `build/push/pull/tag`.

This tool copies the same UX as classic Docker (think Docker v1.12). The intention

is to follow the same style but not be a 100% drop in replacement.  Behaviour and

arguments have been changed to better match the behavior of the Kubernetes ecosystem.



## A single binary



`k3c`, similar to `k3s` and old school docker, is packaged as a single binary, because nothing

is easier for distribution than a static binary.



## Built on Kubernetes Tech (and others)



Fundamentally `k3c` is a built on the [Container Runtime Interface (CRI)](https://github.com/kubernetes/cri-api),

[containerd](https://github.com/containerd/containerd), and [buildkit](https://github.com/moby/buildkit).



## Architecture



`k3c` enables building `k3s`-local images by installing a DaemonSet Pod that runs both `buildkitd` and `k3c agent`

and exposing the gRPC endpoints for these active agents in your cluster via a Service. Once installed, the `k3c` CLI

can inspect your installation and communicate with the backend daemons for image building and manipulation with merely

the KUBECONFIG that was available when invoking `k3c install`. When building `k3c` will talk directly to the `buildkit`

service but all other interactions with the underlying containerd/CRI are mediated by the `k3c agent` (primarily

because the `containerd` client code assumes a certain level of co-locality with the `containerd` installation).



## Building



```bash

# more to come on this front but builds are currently a very manual affair

# git clone --branch=trunk https://github.com/rancher/k3c.git ~/Projects/rancher/k3c

# cd ~/Projects/rancher/k3c

go generate # only necessary when modifying the gRPC protobuf IDL, see Dockerfile for pre-reqs

make ORG= build publish

```



## Running



Have a working `k3s` installation with a working `$HOME/.kube/config` or `$KUBECONFIG`, then:



```bash

# Installation on a single-node cluster

./bin/k3c install --agent-image=docker.io/${ORG}/k3c

```



```bash

# Installation on a multi-node cluster, targeting a Node named "my-builder-node"

./bin/k3c install --agent-image=docker.io/${ORG}/k3c --selector k3s.io/hostname=my-builder-node



```



`k3c` currently works against a single builder node so you must specify a narrow selector when

installing on multi-node clusters. Upon successful installation this node will acquire the "builder" role.



Build images like you would with `docker`



```

$ ./bin/k3c --help

Usage:

  k3c [flags]

  k3c [command]



Available Commands:

  build       Build an image

  help        Help about any command

  images      List images

  install     Install builder component(s)

  pull        Pull an image

  push        Push an image

  rmi         Remove an image

  tag         Tag an image

  uninstall   Uninstall builder component(s)



Flags:

  -x, --context string      kubeconfig context for authentication

      --debug               

      --debug-level int     

  -h, --help                help for k3c

  -k, --kubeconfig string   kubeconfig for authentication

  -n, --namespace string    namespace (default "k3c")

  -v, --version             version for k3c



Use "k3c [command] --help" for more information about a command.

```



## Roadmap



- Automated builds for clients on MacOS (amd64/arm64), Windows (amd64), and Linux client/server (amd64/arm64/arm).



# License



Copyright (c) 2020-2021 [Rancher Labs, Inc.](http://rancher.com)



Licensed under the Apache License, Version 2.0 (the "License");

you may not use this file except in compliance with the License.

You may obtain a copy of the License at



[http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)



Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and

limitations under the License.