Docker 构建在另一个目标下执行指令（多阶段）

Question

我有虚拟 Dockerfile：

FROM python:3.8-alpine3.13 AS python-base

RUN echo http://mirror.yandex.ru/mirrors/alpine/v3.13/main > /etc/apk/repositories; \
    echo http://mirror.yandex.ru/mirrors/alpine/v3.13/community >> /etc/apk/repositories

ENV PYTHONDONTWRITEBYTECODE=1 \
    PYTHONFAULTHANDLER=1 \
    PYTHONUNBUFFERED=1 \
    PYTHONHASHSEED=random

FROM python-base as builder-base

WORKDIR /app
RUN apk update && apk add --no-cache \
    gcc musl-dev postgresql-dev openldap-dev gettext-dev \
    libffi-dev openssl-dev python3-dev jpeg-dev zlib-dev musl-locales \
    musl-locales-lang postgresql-libs libjpeg graphviz-dev ttf-freefont
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY pythonapline .
RUN python manage.py migrate
RUN python manage.py compilemessages
EXPOSE 8000

CMD ["python", "manage.py", "runserver", "0.0.0.0:8000"]

FROM builder-base as development
RUN pip install fastapi
RUN echo 'DEVELOPMENT'

FROM builder-base as test
RUN echo 'TEST'

当我想在目标 test 下构建图像时，我执行命令：

docker build -t myimage --target=test .

但是我注意到目标开发下的指令也被执行了：

....
Step 16/18 : RUN echo 'DEVELOPMENT'
 ---> Running in 4cfa2ed80350
DEVELOPMENT
Removing intermediate container 4cfa2ed80350
 ---> 935d770dfe6d
Step 17/18 : FROM builder-base AS test
 ---> 442c02445aae
Step 18/18 : RUN echo 'TEST'
 ---> Running in 13432a53bec0
TEST
Removing intermediate container 13432a53bec0
 ---> 96e80f6d9603
Successfully built 96e80f6d9603

这是预期的吗？如果不是怎么回事？

Answer 1

--target 选项并不意味着“从这个目标开始”或“只构建这个目标”；意思是“stop at this target”。

因此，如果您指定 --target test，Docker 将运行 test 阶段及其之前的每个阶段。

Docker 构建在另一个目标下执行指令（多阶段）

Docker build performs instructions under another target (multistage)

docker

dockerfile

docker-multi-stage-build