为什么这个多阶段构建中的最终docker镜像如此之大？

Question

在阅读了多阶段docker构建可能实现的巨大图像大小缩减之后，我试图减小用于构建Go二进制文件的Dockerfile的图像大小。我的Dockerfile在下面。

# 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，生成的图像似乎根本没有缩小尺寸。我怀疑golang:alpine图像是以某种方式被包含的。下面是在上面的Dockerfile上运行docker build .的结果的屏幕截图。

alpine:latest图片仅为4.15MB。添加已编译二进制文件的大小（相对较小）我估计最终图像不会超过15MB。但它是407MB。我显然做错了什么！

如何调整我的Dockerfile以生成较小尺寸的图像？

Answer 1

埋在Docker文档的深处，我发现当我开始最终ARG时，我的ENV和FROM定义已被清除。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