带有 GitHub Actions 的命名上下文

您可以定义其他构建上下文FROM name，并使用或在 Dockerfile 中访问它们--from=name。当 Dockerfile 定义同名的阶段时，它会被覆盖。

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

将图像固定到标签

替换alpine:latest为固定的：

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

name: ci

on:
  push:
    branches:
      - "main"

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
      - name: Build
        uses: docker/build-push-action@v5
        with:
          context: .
          build-contexts: |
            alpine=docker-image://alpine:3.19            
          tags: myimage:latest

在后续步骤中使用图像

默认情况下， Docker Setup Buildx 操作用作docker-container构建驱动程序，因此不会自动加载构建的 Docker 映像。

通过命名上下文，您可以重用构建的图像：

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

name: ci

on:
  push:
    branches:
      - "main"

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
        with:
          driver: docker
      - name: Build base image
        uses: docker/build-push-action@v5
        with:
          context: ./base
          file: ./base/Dockerfile
          load: true
          tags: my-base-image:latest
      - name: Build
        uses: docker/build-push-action@v5
        with:
          context: .
          build-contexts: |
            alpine=docker-image://my-base-image:latest            
          tags: myimage:latest

与容器构建器一起使用

如上一节所示，我们没有使用默认 docker-container驱动程序来构建命名上下文。这是因为该驱动程序无法从 Docker 存储加载映像，因为它是隔离的。要解决此问题，您可以使用本地注册表将基础映像推送到工作流程中：

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

name: ci

on:
  push:
    branches:
      - "main"

jobs:
  docker:
    runs-on: ubuntu-latest
    services:
      registry:
        image: registry:2
        ports:
          - 5000:5000
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - 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@v5
        with:
          context: ./base
          file: ./base/Dockerfile
          tags: localhost:5000/my-base-image:latest
          push: true
      - name: Build
        uses: docker/build-push-action@v5
        with:
          context: .
          build-contexts: |
            alpine=docker-image://localhost:5000/my-base-image:latest            
          tags: myimage:latest