├── Dockerfile.example ├── Dockerfile ├── README.md └── LICENSE /Dockerfile.example: -------------------------------------------------------------------------------- 1 | FROM alpine:latest 2 | 3 | RUN touch .i-was-here 4 | CMD date 5 | -------------------------------------------------------------------------------- /Dockerfile: -------------------------------------------------------------------------------- 1 | FROM moby/buildkit:v0.4.0 2 | 3 | RUN mkdir example-build 4 | COPY Dockerfile.example ./example-build 5 | WORKDIR ./example-build 6 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # BuildKit example for in-cluster build 2 | 3 | This project provides a simple example, using [BuildKit](https://github.com/moby/buildkit) to provide in-cluster 4 | build capabilities without the use of a host-provided Docker runtime (or 5 | having to rely on a Docker-in-Docker configuration). 6 | 7 | ## Background 8 | 9 | One recurring pattern in the Kubernetes world involves a potential need 10 | to build containers within the cluster (versus using an out-of-cluster service). 11 | When 99.9% of Kubernetes clusters were built with the Docker 12 | engine backing each node of the cluster, one common "hack" of the wall 13 | between Kubernetes and the host was to use a privileged pod with the Docker API 14 | socket mounted, allowing a container to perform `docker build` commands 15 | against the host-installed Docker engine. Of course once a 16 | container has access to the Docker socket, there are other worrying security 17 | concerns given the capability for that special container to now interfere and 18 | interact with all other containers on the host. One potential mitigation is 19 | extra isolation, like a Docker-in-Docker (DinD)-based solution. 20 | 21 | Fast forward to today and Docker is not necessarily the default container 22 | runtime underneath many Kubernetes clusters and is potentially not even 23 | installed on cluster worker nodes given the advancement of CRI-compliant runtimes 24 | like containerd and cri-o, among others. This anti-pattern of mounting the 25 | Docker socket in a pod can be replaced with tools like BuildKit, which require 26 | no Docker API socket and can depend on simply the OCI-compliant `runc` executor, 27 | or containerd. 28 | 29 | This repository provides a small skeleton example, providing an in-cluster 30 | buildkitd pod listening on a TCP port so that in-cluster builds can 31 | use a rootless, unprivileged BuildKit to perform container builds. 32 | 33 | ## Other Options 34 | 35 | While I wanted to learn more about BuildKit internals and usage specifically, don't 36 | ignore that there are other more polished frameworks that provide this at a higher 37 | level already. Many of them build on BuildKit, or at least provide BuildKit as an 38 | option. Here is a short list of other projects to consider if you are looking for 39 | more complete solutions: 40 | 41 | - [img](https://github.com/genuinetools/img) from [jessfraz](https://github.com/jessfraz). Related [blog post](https://blog.jessfraz.com/post/building-container-images-securely-on-kubernetes/) 42 | - [Kaniko](https://github.com/GoogleContainerTools/kaniko) from [Google's ContainerTools](https://github.com/GoogleContainerTools) project. 43 | - [Knative build](https://github.com/knative/build), part of the [Knative](https://cloud.google.com/knative/) project. [Nice blog](https://starkandwayne.com/blog/build-docker-images-inside-kubernetes-with-knative-build/) on using it from [DrNic](https://github.com/drnic). 44 | - More details on different in-cluster build options within Knative in this [blog post](https://www.morethanseven.net/2018/07/29/knative-build-with-docker-buildkit-img/) from Gareth Rushgrove 45 | 46 | ## Using this example repository 47 | 48 | ### Expectations 49 | 50 | You have a Kubernetes cluster for which you have administrative access to 51 | deploy a pod. The underlying runtime backing your worker nodes is immaterial as 52 | BuildKit will not use that runtime in this example. 53 | 54 | This example will have you deploy the BuildKit daemon, relying on `runc` as the 55 | build worker, using the pre-built DockerHub image for rootless BuildKit [v0.4.0](https://github.com/moby/buildkit/releases/tag/v0.4.0), 56 | released in March 2019. 57 | 58 | You will then build an image based off the existing v0.4.0 BuildKit image to 59 | have the `buildctl` command and a simple `Dockerfile.example` in a single image 60 | for use within a Kubernetes batch job to demonstrate calling the BuildKit daemon 61 | pod over TCP to build a container. You can tag and push this image to a registry 62 | as long as you provide the proper secrets to log into your registry, using 63 | BuildKit's support for registry authentication and push. The example will use a 64 | manually created secret to demonstrate this with DockerHub, but can be used with 65 | any registry. 66 | 67 | ### Demonstration steps 68 | 69 | Steps below assume you have cloned this repository and your current working directory is in this repository. 70 | 71 | 1. Deploy the buildkitd pod in your cluster. No modifications should be necessary to [`buildkitd.yaml`](https://github.com/estesp/buildkit-cluster-example/blob/master/buildkitd.yaml): 72 | 73 | ``` 74 | $ kubectl apply -f buildkitd.yaml 75 | ``` 76 | 77 | **NOTE:** *For a discussion on why this pod is still privileged, please [read this document](https://github.com/moby/buildkit/blob/v0.4.0/docs/rootless.md#security-consideration) from the BuildKit maintainers. TL;DR work is underway to remove this requirement.* 78 | 79 | 2. Create a secret with any required Docker credentials from a local Docker installation where you already are logged in to desired registries: 80 | 81 | ``` 82 | $ kubectl create secret generic dockerconfig --from-file=/home//.docker/config.json 83 | ``` 84 | 85 | **NOTE:** *This will not work if done from a Mac OS "Docker Desktop" installation where system credential helpers are used for storing your credentials.* 86 | 87 | 3. Modify the [`build-example.yaml`](https://github.com/estesp/buildkit-cluster-example/blob/master/build-example.yaml) batch job spec for your desired settings for (a) the image you want to use, and (b) the push target in the `args` section, after the `--exporter-opt` field. You can either build the [`Dockerfile`](https://github.com/estesp/buildkit-cluster-example/blob/master/Dockerfile) in the root of this 88 | repo with your own `Dockerfile.example` (or any other changes you wish to make) or simply use the `estesp/buildexample:1.0` already listed, which has been built from that `Dockerfile` already. 89 | 90 | 4. When you are satisfied with your copy of the `build-example.yaml` you can apply it to your cluster to run a build against the BuildKit daemon already running, and push an image to your desired target: 91 | 92 | ``` 93 | $ kubectl apply -f build-example.yaml 94 | ``` 95 | 96 | 5. You can `kubectl get po` to see that your batch job ran properly, and use `kubectl logs` to show the output from your BuildKit run. 97 | 98 | In my case: 99 | 100 | ``` 101 | $ kubectl get po 102 | NAME READY STATUS RESTARTS AGE 103 | builder-d44n9 0/1 Completed 0 88m 104 | buildkitd-765fcc4854-htxbt 1/1 Running 0 3h41m 105 | ``` 106 | 107 | And my successful image build and push: 108 | 109 | ``` 110 | $ kubectl logs builder-d44n9 111 | time="2019-03-22T19:46:01Z" level=warning msg="--exporter is deprecated. Please use --output type 112 | =[,=] instead." 113 | time="2019-03-22T19:46:01Z" level=warning msg="--frontend-opt = is deprecated. Please use --opt 114 | = instead." 115 | 116 | #2 [internal] load build definition from Dockerfile.example 117 | #2 digest: sha256:e323acd1c1ceb435985588acb4550e981ed92f1a820e72beea0350fe50ffa621 118 | #2 name: "[internal] load build definition from Dockerfile.example" 119 | #2 started: 2019-03-22 19:46:01.065994531 +0000 UTC 120 | #2 completed: 2019-03-22 19:46:01.066102728 +0000 UTC 121 | #2 duration: 108.197µs 122 | #2 started: 2019-03-22 19:46:01.066222014 +0000 UTC 123 | #2 completed: 2019-03-22 19:46:01.079980927 +0000 UTC 124 | #2 duration: 13.758913ms 125 | #2 transferring dockerfile: 39B done 126 | 127 | 128 | #1 [internal] load .dockerignore 129 | #1 digest: sha256:acce6bf27717d36e9a4ea09664e3d0b1342bce019e65d1b679f46203bbcf43b4 130 | #1 name: "[internal] load .dockerignore" 131 | #1 started: 2019-03-22 19:46:01.065710708 +0000 UTC 132 | #1 completed: 2019-03-22 19:46:01.065791408 +0000 UTC 133 | #1 duration: 80.7µs 134 | #1 started: 2019-03-22 19:46:01.06590812 +0000 UTC 135 | #1 completed: 2019-03-22 19:46:01.076959812 +0000 UTC 136 | #1 duration: 11.051692ms 137 | #1 transferring context: 2B done 138 | 139 | 140 | #3 [internal] load metadata for docker.io/library/alpine:latest 141 | #3 digest: sha256:d4fb25f5b5c00defc20ce26f2efc4e288de8834ed5aa59dff877b495ba88fda6 142 | #3 name: "[internal] load metadata for docker.io/library/alpine:latest" 143 | #3 started: 2019-03-22 19:46:01.101981096 +0000 UTC 144 | #3 completed: 2019-03-22 19:46:01.538928609 +0000 UTC 145 | #3 duration: 436.947513ms 146 | 147 | 148 | #4 [1/2] FROM docker.io/library/alpine:latest@sha256:644fcb1a676b5165371437... 149 | #4 digest: sha256:d170cf83c5743380c000554f8ece996d64f35677d36744df8b470ff41cfded6a 150 | #4 name: "[1/2] FROM docker.io/library/alpine:latest@sha256:644fcb1a676b5165371437feaa922943aaf7afcf 151 | a8bfee4472f6860aad1ef2a0" 152 | #4 started: 2019-03-22 19:46:01.539572137 +0000 UTC 153 | #4 completed: 2019-03-22 19:46:01.539856953 +0000 UTC 154 | #4 duration: 284.816µs 155 | #4 resolve docker.io/library/alpine:latest@sha256:644fcb1a676b5165371437feaa922943aaf7afcfa8bfee4472f6860aad 156 | 1ef2a0 done 157 | #5 [2/2] RUN touch .i-was-here 158 | #5 digest: sha256:711798196f4307d0c80e356059f32e62ac46653449125c1c65f467b64f19e658 159 | #5 name: "[2/2] RUN touch .i-was-here" 160 | #5 started: 2019-03-22 19:46:01.540170107 +0000 UTC 161 | #5 completed: 2019-03-22 19:46:01.540209588 +0000 UTC 162 | #5 duration: 39.481µs 163 | #5 cached: true 164 | 165 | 166 | #6 exporting to image 167 | #6 digest: sha256:b77b4e1dd2dfbd75d86a8ab4d3a2911fab70ec665fb2a05cb3a5de4f8a048e42 168 | #6 name: "exporting to image" 169 | #6 started: 2019-03-22 19:46:01.540282029 +0000 UTC 170 | #6 exporting layers done 171 | #6 exporting manifest sha256:d2138b9afd64b4f11e89469538ebb158d63087b8b8a42aab9a22d680aceffb9e done 172 | #6 exporting config sha256:846f932de93756f788053508a6e162c026f2fddbdd22cfe37646a85c07c5ba1d 0.0s done 173 | #6 pushing layers 174 | #6 pushing layers 0.4s done 175 | #6 pushing manifest for docker.io/estesp/mybkimg:latest 176 | #6 completed: 2019-03-22 19:46:02.070280786 +0000 UTC 177 | #6 duration: 529.998757ms 178 | #6 pushing manifest for docker.io/estesp/mybkimg:latest 0.1s done 179 | ``` 180 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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