#TIL : Build lightweight image by using multistage

Docker is great tool to build a pull-n-run application. But sometimes, your image will be large if you build image from a big base image which has heavy compliling toolbox.

Ex:

One-stage build

FROM golang:1.9.2
WORKDIR /go/src/github.com/khanhicetea/test/
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build .
ENTRYPOINT ["/go/src/github.com/khanhicetea/test/test"]

Multi-stage builds

FROM golang:1.9.2
WORKDIR /go/src/github.com/khanhicetea/test/
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build .

FROM scratch
COPY --from=0 /go/src/github.com/khanhicetea/test/test .
ENTRYPOINT ["/test"]

So final image will only contains /test excutable file. COPY --from=0 means COPY from build has index 0 in Dockerfile.