GitHub Actions 中的命名上下文

您可以定义附加的构建上下文,并在 Dockerfile 中使用 FROM name--from=name 访问它们。当 Dockerfile 定义了同名阶段时,它将被覆盖。

这在 GitHub Actions 中非常有用,可以重用其他构建的结果或将镜像固定到工作流程中的特定标签。

将镜像固定到标签

将 alpine:latest 替换为已固定的标签

# syntax=docker/dockerfile:1
FROM alpine
RUN echo "Hello World"
name: ci

on:
  push:

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Build
        uses: docker/build-push-action@v6
        with:
          build-contexts: |
            alpine=docker-image://alpine:3.21
          tags: myimage:latest

在后续步骤中使用镜像

默认情况下,Docker Setup Buildx action 使用 docker-container 作为构建驱动,因此构建的 Docker 镜像不会自动加载。

使用命名上下文,您可以重用已构建的镜像

# syntax=docker/dockerfile:1
FROM alpine
RUN echo "Hello World"
name: ci

on:
  push:

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
        with:
          driver: docker

      - name: Build base image
        uses: docker/build-push-action@v6
        with:
          context: "{{defaultContext}}:base"
          load: true
          tags: my-base-image:latest

      - name: Build
        uses: docker/build-push-action@v6
        with:
          build-contexts: |
            alpine=docker-image://my-base-image:latest
          tags: myimage:latest

与容器构建器一起使用

如前所述,在使用命名上下文进行构建时,我们没有使用默认的 docker-container 驱动。这是因为此驱动是隔离的,无法从 Docker store 加载镜像。要解决此问题,您可以在工作流程中使用本地仓库来推送基础镜像。

# syntax=docker/dockerfile:1
FROM alpine
RUN echo "Hello World"
name: ci

on:
  push:

jobs:
  docker:
    runs-on: ubuntu-latest
    services:
      registry:
        image: registry:2
        ports:
          - 5000:5000
    steps:
      - name: Set up QEMU
        uses: docker/setup-qemu-action@v3

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
        with:
          # network=host driver-opt needed to push to local registry
          driver-opts: network=host

      - name: Build base image
        uses: docker/build-push-action@v6
        with:
          context: "{{defaultContext}}:base"
          tags: localhost:5000/my-base-image:latest
          push: true

      - name: Build
        uses: docker/build-push-action@v6
        with:
          build-contexts: |
            alpine=docker-image://localhost:5000/my-base-image:latest
          tags: myimage:latest
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