如何利用FROM导入本地其他目录Dockerfile，实现Docker多阶段构建？

Great question! Let’s break down your two core questions clearly:

1. Can FROM directly reference a Dockerfile in another local directory? #

No, Docker’s FROM directive can’t point directly to a Dockerfile path—it only accepts the name (or ID) of an already-built image (either local or from a remote registry).

If you want to reuse the build logic from a Dockerfile in another directory, here are two practical workarounds:

• First build that directory’s Dockerfile into a named image, then reference it in your multi-stage build:

  # Build the external stage into a local image first
  docker build -t my-shared-builder ./path/to/other/directory
  

  Then in your main Dockerfile:

  FROM my-shared-builder as builder
  # Use artifacts from this stage in subsequent steps
  
  FROM alpine:latest
  COPY --from=builder /app/dist /usr/local/app
  CMD ["/usr/local/app/start"]
  

• Use the docker build command’s -f flag to specify the external Dockerfile during a multi-stage build, paired with --target if you only need a specific stage from it.

2. Can I add other Dockerfiles to the current build and use FROM with them? #

You can’t "import" a Dockerfile into another one by copying it with ADD/COPY and expecting FROM to execute its content—ADD only places the Dockerfile as a static file inside the image, not as executable build instructions.

Instead, the standard approach is to integrate the content of the external Dockerfiles directly into your main multi-stage Dockerfile. For example:
Suppose you have a backend/Dockerfile with:

FROM python:3.11
WORKDIR /backend
ADD requirements.txt ./
RUN pip install --no-cache-dir -r requirements.txt
ADD . ./
RUN python manage.py collectstatic

And a frontend/Dockerfile that needs to use backend assets, you can merge them into a single multi-stage Dockerfile:

# Stage 1: Reuse logic from backend/Dockerfile
FROM python:3.11 as backend-builder
WORKDIR /backend
ADD ./backend/requirements.txt ./
RUN pip install --no-cache-dir -r requirements.txt
ADD ./backend/ ./
RUN python manage.py collectstatic

# Stage 2: Your final frontend image
FROM nginx:alpine
COPY --from=backend-builder /backend/static /usr/share/nginx/html/static
ADD ./frontend/dist /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

If you want to keep Dockerfiles separate but automate the chained build, you can write a simple shell script to build each stage in order and pass artifacts between them.

内容的提问来源于stack exchange，提问作者Baily