利用 docker buildx 构建多平台镜像
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- 7 minutes read - 1326 words什么是 docker buildx
Docker Buildx是一个CLI插件，它扩展了Docker命令，完全支持Moby BuildKit builder toolkit提供的功能。它提供了与docker build相同的用户体验，并提供了许多新功能，如创建作用域生成器实例和针对多个节点并发构建。
Docker Buildx包含在Docker 19.03中，并与以下Docker Desktop版本捆绑在一起。请注意，必须启用“实验特性”选项才能使用Docker Buildx。
Docker Desktop Enterprise version 2.1.0 Docker Desktop Edge version 2.0.4.0 or higher
用法
Usage: docker buildx [OPTIONS] COMMAND
Extended build capabilities with BuildKit
Options:
--builder string Override the configured builder instance
Management Commands:
imagetools Commands to work on images in registry
Commands:
bake Build from a file
build Start a build
create Create a new builder instance
du Disk usage
inspect Inspect current builder instance
ls List builder instances
prune Remove build cache
rm Remove a builder instance
stop Stop builder instance
use Set the current builder instance
version Show buildx version information
Run 'docker buildx COMMAND --help' for more information on a command
一般用到 create、ls 和 rm 就可以了
创建 builder 实例
由于 Docker 默认的 builder 实例不支持同时指定多个 –platform，所有我们必须先创建一个 builder 实例
$ docker buildx create --use --name=mybuilder-cn --driver docker-container
--use 表示使用当前创建的 builder 实例
--name 实例名称
--driver 实例驱动(docker、 docker-container 和 kubernetes)
更多用法通过命令 docker buildx create -h 查看
查看新实例
NAME/NODE DRIVER/ENDPOINT STATUS PLATFORMS
mybuilder-cn * docker-container
mybuilder-cn0 unix:///var/run/docker.sock inactive
default docker
default default running linux/amd64, linux/386
其中 * 表示当前正在使用的builder实例。
我们查看一下实例详细信息
$ docker buildx inspect
Name: mybuilder-cn
Driver: docker-container
Nodes:
Name: mybuilder-cn0
Endpoint: unix:///var/run/docker.sock
Status: running
Platforms: linux/amd64, linux/386
构建镜像
创建Dockerfile 文件
FROM --platform=$TARGETPLATFORM alpine
RUN uname -a > /os.txt
CMD cat /os.txt
这里使用到了变量 TARGETPLATFORM, 内置的一些变量在本文下方了解
构建指定平台
使用 docker buildx build 命令构建镜像
$ docker buildx build .
WARN[0000] No output specified for docker-container driver. Build result will only remain in the build cache. To push result image into registry use --push or to load image into docker use --load
[+] Building 32.9s (6/6) FINISHED
=> [internal] booting buildkit 25.4s
=> => pulling image moby/buildkit:buildx-stable-1 23.9s
=> => creating container buildx_buildkit_mybuilder-cn0 1.5s
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 115B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [internal] load metadata for docker.io/library/alpine:latest 5.1s
=> [1/2] FROM docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 1.9s
=> => resolve docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> => sha256:a0d0a0d46f8b52473982a3c466318f479767577551a53ffc9074c9fa7035982e 2.81MB / 2.81MB 1.8s
=> => extracting sha256:a0d0a0d46f8b52473982a3c466318f479767577551a53ffc9074c9fa7035982e 0.1s
=> [2/2] RUN uname -a > /os.txt
从上面的输出可以看出，构建步骤大概如下：
- 加载引导buildkit
- 下载镜像文件 image moby/buildkit:buildx-stable-1
- 使用镜像创建容器 buildx_buildkit_mybuilder-cn0
- 将当前 Dockerfile 文件传输到容器内
- 在容器内下载镜像 docker.io/library/alpine:latest
- 运行Dockerfile中的 RUN 指令
如果你用 docker ps 命令查看容器的话，会看到创建了一个 buildkitd 容器
构建多平台镜像
也可以指定一些设置，如构建的目标平台等
$ docker buildx build --platform linux/arm,linux/arm64,linux/amd64 -t cfanbo/hello . --push
[+] Building 18.4s (18/18) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 115B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [linux/amd64 internal] load metadata for docker.io/library/alpine:latest 2.3s
=> [linux/arm64 internal] load metadata for docker.io/library/alpine:latest 2.4s
=> [linux/arm/v7 internal] load metadata for docker.io/library/alpine:latest 2.7s
=> [auth] library/alpine:pull token for registry-1.docker.io 0.0s
=> [auth] library/alpine:pull token for registry-1.docker.io 0.0s
=> [auth] library/alpine:pull token for registry-1.docker.io 0.0s
=> [linux/arm/v7 1/2] FROM docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> => resolve docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> [linux/arm64 1/2] FROM docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> => resolve docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> [linux/amd64 1/2] FROM docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> => resolve docker.io/library/alpine@sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a 0.0s
=> CACHED [linux/arm/v7 2/2] RUN uname -a > /os.txt 0.0s
=> CACHED [linux/arm64 2/2] RUN uname -a > /os.txt 0.0s
=> CACHED [linux/amd64 2/2] RUN uname -a > /os.txt 0.0s
=> exporting to image 15.5s
=> => exporting layers 0.0s
=> => exporting manifest sha256:fc3842a7caa48e4124d6a76dcb1cff3944e55eeefd5daeb21dfe8201de8d856c 0.0s
=> => exporting config sha256:4db341c87f5e347b12f2f8955da60ac4db9bcf2bc17aed18079d2ac55b759cca 0.0s
=> => exporting manifest sha256:91bcf398194707f1b9ce9fe6b7dcc29b809dc3278cddc1a13cb5dc76d60bb281 0.0s
=> => exporting config sha256:e0f919da8544b23e919c1257c6b40c54a4c9114447e1d637f4d965204757dbab 0.0s
=> => exporting manifest sha256:4a5479758b57441933984c2209bccff4f0c47c7dd74be95b4b22162d105e639a 0.0s
=> => exporting config sha256:6af666ad21adae02a9147dfcec4c9397e2be9e12d5861614e5fc20a287fe4086 0.0s
=> => exporting manifest list sha256:e8758d75c4d6cf2a633c645616c1d4f76006ee0503d7b16532a744346bca0cf7 0.0s
=> => pushing layers 12.4s
=> => pushing manifest for docker.io/cfanbo/hello:latest@sha256:e8758d75c4d6cf2a633c645616c1d4f76006ee0503d7b16532a744346bca0cf7 3.1s
=> [auth] cfanbo/hello:pull,push token for registry-1.docker.io 0.0s
=> [auth] cfanbo/hello:pull,push token for registry-1.docker.io 0.0s
=> [auth] cfanbo/hello:pull,push token for registry-1.docker.io
这里我们指定了三个平台，它们将同时分别进行构建。由于我这里多次执行了构建命令，所以三个平台构建过程中都显示 CACHED，表示用到了缓存。
我这里 平台的用户名为 cfanbo, 替换为自己的 Docker Hub 用户名。
--push 参数表示将构建好的镜像推送到 Docker 仓库,在构建前记得先执行 docker login 命令登录。这里通过 可以看到分别为三个平台构建了不同的镜像。
- 查看镜像信息
$ docker buildx imagetools inspect cfanbo/hello
Name: docker.io/cfanbo/hello:latest
MediaType: application/vnd.docker.distribution.manifest.list.v2+json
Digest: sha256:e8758d75c4d6cf2a633c645616c1d4f76006ee0503d7b16532a744346bca0cf7
Manifests:
Name: docker.io/cfanbo/hello:latest@sha256:fc3842a7caa48e4124d6a76dcb1cff3944e55eeefd5daeb21dfe8201de8d856c
MediaType: application/vnd.docker.distribution.manifest.v2+json
Platform: linux/arm/v7
Name: docker.io/cfanbo/hello:latest@sha256:91bcf398194707f1b9ce9fe6b7dcc29b809dc3278cddc1a13cb5dc76d60bb281
MediaType: application/vnd.docker.distribution.manifest.v2+json
Platform: linux/arm64
Name: docker.io/cfanbo/hello:latest@sha256:4a5479758b57441933984c2209bccff4f0c47c7dd74be95b4b22162d105e639a
MediaType: application/vnd.docker.distribution.manifest.v2+json
Platform: linux/amd64
- 验证镜像
### Linux
$ docker run --rm cfanbo/hello:latest
Linux buildkitsandbox 5.11.0-31-generic #33-Ubuntu SMP Wed Aug 11 13:19:04 UTC 2021 x86_64 Linux
### aarch64
$ sudo docker run --rm cfanbo/hello:latest
Linux buildkitsandbox 5.11.0-31-generic #33-Ubuntu SMP Wed Aug 11 13:19:04 UTC 2021 aarch64 Linux
- 优化
首先我们了解一些 Dockerfile内置的变量
Dockerfile 支持如下架构相关的变量
TARGETPLATFORM 构建镜像的目标平台，例如 linux/amd64, linux/arm/v7, windows/amd64。
TARGETOS 构建镜像目标平台的 OS 类型，例如 linux, windows
TARGETARCH 构建镜像目标平台的架构类型，例如 amd64, arm
TARGETVARIANT 构建镜像目标平台的变种，该变量可能为空，例如 v7
BUILDPLATFORM 构建镜像所使用的主机平台，例如 linux/amd64
BUILDOS 构建镜像所使用主机平台 的 OS 类型，例如 linux
BUILDARCH 构建镜像所使用主机平台 的架构类型，例如 amd64
BUILDVARIANT构建镜像所使用主机平台 的变种，该变量可能为空，例如 v7
使用举例 例如我们要构建支持 linux/arm/v7 和 linux/amd64 两种架构的镜像。假设已经生成了两个平台对应的二进制文件：
bin/dist-linux-arm
bin/dist-linux-amd64
那么 Dockerfile 可以这样书写：
FROM scratch
# 使用变量必须申明
ARG TARGETOS
ARG TARGETARCH
COPY bin/dist-${TARGETOS}-${TARGETARCH} /dist
ENTRYPOINT ["dist"]
上面的方法虽然可以实现，但还有一个比较麻烦的问题。我们要构建的不同平台的二进制程序，每次都需要手动指定目标一个平台再构建，法子太笨了，有没有更简单高效的的办法呢？
这里我们可以利用另一个变量 BUILDPLATFORM，再利用两阶段构建来解决这个问题，此时的 Dockerfile 内容为
FROM --platform=$BUILDPLATFORM golang:1.20-alpine AS builder
ARG TARGETOS
ARG TARGETARCH
WORKDIR /app
ADD . .
RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o hello .
FROM --platform=$TARGETPLATFORM alpine:latest
WORKDIR /app
COPY --from=builder /app/hello .
CMD ["./hello"]
我们写一个简单的golang程序
package main
import (
"fmt"
"runtime"
)
func main() {
fmt.Printf("Hello, %s/%s!n", runtime.GOOS, runtime.GOARCH)
}
此时重新构建镜像
$ docker buildx build --platform linux/arm,linux/arm64,linux/amd64 -t cfanbo/hello:v2 . --push
[+] Building 833.3s (28/29) docker-container:mybuilder-cn
=> [internal] booting buildkit 223.0s
=> => pulling image moby/buildkit:buildx-stable-1 166.2s
=> => creating container buildx_buildkit_mybuilder-cn0 42.9s
=> [internal] load build definition from Dockerfile 3.0s
=> => transferring dockerfile: 316B 0.2s
=> [internal] load .dockerignore 2.0s
=> => transferring context: 2B 0.2s
=> [linux/amd64 internal] load metadata for docker.io/library/alpine:latest 15.9s
=> [linux/amd64 internal] load metadata for docker.io/library/golang:1.20-alpine 600.3s
=> [auth] library/alpine:pull token for registry-1.docker.io 2.0s
=> [linux/arm64 internal] load metadata for docker.io/library/alpine:latest 14.9s
=> [linux/arm/v7 internal] load metadata for docker.io/library/alpine:latest 14.5s
=> [auth] library/golang:pull token for registry-1.docker.io 0.0s
=> [auth] library/alpine:pull token for registry-1.docker.io 0.6s
=> [linux/amd64 builder 1/4] FROM docker.io/library/golang:1.20-alpine@sha256:7efb78dac256c450d194e556e96f80936528335033a26d703ec8146cec8c2090 380.6s
=> => resolve docker.io/library/golang:1.20-alpine@sha256:7efb78dac256c450d194e556e96f80936528335033a26d703ec8146cec8c2090 0.2s
=> => sha256:8fa91ef8ef8a80329ba55630fd46f90a465c3f58322192320a32044c49f7daad 156B / 156B 1.1s
=> => sha256:f8f5e977ad9826fc24b1db3f0dbb1ea9a261cd25d4657a9d50e7bf435638cd11 101.36MB / 101.36MB 341.7s
=> => sha256:7f9bcf943fa5571df036dca6da19434d38edf546ef8bb04ddbc803634cc9a3b8 284.71kB / 284.71kB 5.2s
=> => extracting sha256:7f9bcf943fa5571df036dca6da19434d38edf546ef8bb04ddbc803634cc9a3b8 2.0s
=> => extracting sha256:f8f5e977ad9826fc24b1db3f0dbb1ea9a261cd25d4657a9d50e7bf435638cd11 36.8s
=> => extracting sha256:8fa91ef8ef8a80329ba55630fd46f90a465c3f58322192320a32044c49f7daad 0.1s
=> [linux/amd64 stage-1 1/3] FROM docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 38.2s
=> => resolve docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 0.2s
=> => sha256:31e352740f534f9ad170f75378a84fe453d6156e40700b882d737a8f4a6988a3 3.40MB / 3.40MB 34.8s
=> => extracting sha256:31e352740f534f9ad170f75378a84fe453d6156e40700b882d737a8f4a6988a3 3.0s
=> [linux/arm/v7 stage-1 1/3] FROM docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 32.2s
=> => resolve docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 0.2s
=> => sha256:633ba29fd335042456b6e2c073636f6fa30de56f1331c442914739b92a479974 2.90MB / 2.90MB 29.7s
=> => extracting sha256:633ba29fd335042456b6e2c073636f6fa30de56f1331c442914739b92a479974 1.8s
=> [linux/arm64 stage-1 1/3] FROM docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 38.5s
=> => resolve docker.io/library/alpine:latest@sha256:82d1e9d7ed48a7523bdebc18cf6290bdb97b82302a8a9c27d4fe885949ea94d1 0.2s
=> => sha256:8c6d1654570f041603f4cef49c320c8f6f3e401324913009d92a19132cbf1ac0 3.33MB / 3.33MB 34.5s
=> => extracting sha256:8c6d1654570f041603f4cef49c320c8f6f3e401324913009d92a19132cbf1ac0 3.2s
=> [internal] load build context 0.6s
=> => transferring context: 544B 0.0s
=> [linux/arm/v7 stage-1 2/3] WORKDIR /app 0.9s
=> [linux/amd64 stage-1 2/3] WORKDIR /app 1.4s
=> [linux/arm64 stage-1 2/3] WORKDIR /app 1.5s
=> [linux/amd64 builder 2/4] WORKDIR /app 2.9s
=> [linux/amd64 builder 3/4] ADD . . 0.3s
=> [linux/amd64 builder 4/4] RUN GOOS=linux GOARCH=arm64 go build -o hello . 157.8s
=> [linux/amd64 builder 4/4] RUN GOOS=linux GOARCH=amd64 go build -o hello . 158.4s
=> [linux/amd64 builder 4/4] RUN GOOS=linux GOARCH=arm go build -o hello . 156.1s
=> [linux/arm/v7 stage-1 3/3] COPY --from=builder /app/hello . 0.3s
=> [linux/arm64 stage-1 3/3] COPY --from=builder /app/hello . 0.2s
=> [linux/amd64 stage-1 3/3] COPY --from=builder /app/hello . 0.3s
=> exporting to image 37.3s
=> => exporting layers 1.4s
=> => exporting manifest sha256:148ce9bd7ff585e4fd51208cc609012b010a6688ceaf432ea1c9931ed25966b8 0.0s
=> => exporting config sha256:9212722eba519486331427497448bfa025bcf8430f4fc63e59eae029e6e9572c 0.0s
=> => exporting manifest sha256:fe88bf0f3ea814d797d1981c1d9807674dab23a767130da5100ac12374581a14 0.0s
=> => exporting config sha256:634f645cb55a93ddf999ce79b04878c9859e238f01f556876278f8abf1b76395 0.0s
=> => exporting manifest sha256:d4f1a318546840a94de6e1a3e4f609097eb63ba7338ebdf1813bf364a8b4d4ad 0.0s
=> => exporting config sha256:6053d6935151693c906d4adfb2ab0545b28f88a35e18940520bd20a6c7dabf52 0.0s
=> => exporting manifest list sha256:c7281230c39c54ae2556fc8ec711bccd95cee6d89ce218c65fb36346c5022a53 0.0s
=> => pushing layers 31.2s
=> => pushing manifest for docker.io/cfanbo/hello:v2@sha256:c7281230c39c54ae2556fc8ec711bccd95cee6d89ce218c65fb36346c5022a53 4.5s
=> [auth] cfanbo/hello:pull,push token for registry-1.docker.io 0.0s
=> [auth] cfanbo/hello:pull,push token for registry-1.docker.io 0.0s
从日志中可以看到，首先在基础镜像 golang:1.20-alpine 里通过设置不同的环境变量实现了 golang 交叉编译，然后在对每个不同的架构平台进行镜像构建，本次生成的镜像为 hello:v2。
我们用 manifest 命令验证一下
$ docker manifest inspect cfanbo/hello:v2
{
"schemaVersion": 2,
"mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
"manifests": [
{
"mediaType": "application/vnd.docker.distribution.manifest.v2+json",
"size": 945,
"digest": "sha256:148ce9bd7ff585e4fd51208cc609012b010a6688ceaf432ea1c9931ed25966b8",
"platform": {
"architecture": "arm",
"os": "linux",
"variant": "v7"
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v2+json",
"size": 945,
"digest": "sha256:fe88bf0f3ea814d797d1981c1d9807674dab23a767130da5100ac12374581a14",
"platform": {
"architecture": "arm64",
"os": "linux"
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v2+json",
"size": 945,
"digest": "sha256:d4f1a318546840a94de6e1a3e4f609097eb63ba7338ebdf1813bf364a8b4d4ad",
"platform": {
"architecture": "amd64",
"os": "linux"
}
}
]
}
可以看到镜像包含了不同构架平台的层信息。
测试一下(amd64)
$ docker run --rm cfanbo/hello:v2
Hello, linux/amd64!
清理工作
删除cache 和 builder instance
$ docker buildx prune
$ docker buildx rm mybuilder-cn
参考资料
- https://docs.docker.com/buildx/working-with-buildx/
- https://docs.docker.com/engine/reference/commandline/buildx/