为什么我的最终 docker 镜像在这个多阶段构建中如此大？

Question

在阅读了多阶段 docker 构建可能实现的巨大图像大小减小之后，我尝试缩小用于构建 Go 二进制文件的 Dockerfile 的图像大小。我的 Dockerfile 如下。

# Configure environment and build settings.
FROM golang:alpine AS buildstage
ARG name=ddmnh
ENV GOPATH=/gopath

# Create the working directory.
WORKDIR ${GOPATH}

# Copy the repository into the image.
ADD . ${GOPATH}

# Move to GOPATH, install dependencies and build the binary.
RUN cd ${GOPATH} && go get ${name}
RUN CGO_ENABLED=0 GOOS=linux go build ${name}

# Multi-stage build, we just use plain alpine for the final image.
FROM alpine:latest

# Copy the binary from the first stage.
COPY --from=buildstage ${GOPATH}/${name} ./${name}
RUN chmod u+x ./${name}

# Expose Port 80.
EXPOSE 80

# Set the run command.
CMD ./ddmnh

然而，生成的图像的尺寸似乎根本没有缩小。我怀疑该golang:alpine图像以某种方式被包含在内。docker build .下面是上面 Dockerfile的运行结果截图。

图像alpine:latest只有 4.15MB。添加编译后的二进制文件的大小（相对较小），我预计最终图像不会超过 15MB。但它是 407MB。我显然做错了什么！

如何调整 Dockerfile 以生成较小尺寸的映像？

Answer 1

深入研究 Docker 文档后，我发现当ARG我ENV开始最终的FROM. 重新定义它们解决了这个问题：

# Configure environment and build settings.
FROM golang:alpine AS buildstage
ARG name=ddmnh
ENV GOPATH=/gopath

# Create the working directory.
WORKDIR ${GOPATH}

# Copy the repository into the image.
ADD . ${GOPATH}

# Move to GOPATH, install dependencies and build the binary.
RUN cd ${GOPATH} && go get ${name}
RUN CGO_ENABLED=0 GOOS=linux go build ${name}

# Multi-stage build, we just use plain alpine for the final image.
FROM alpine:latest
ARG name=ddmnh
ENV GOPATH=/gopath

# Copy the binary from the first stage.
COPY --from=buildstage ${GOPATH}/${name} ./${name}
RUN chmod u+x ./${name}

# Expose Port 80.
EXPOSE 80

# Set the run command.
CMD ./ddmnh