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Our first multi-stage Dockerfile

The objective here is to try to use multi-stage images in practice. To this end we will change our Dockerfile to:

  • give a nickname to the first stage: compiler

  • add a second stage using the same ubuntu base image

  • add the hello binary to the second stage

  • make sure that CMD is in the second stage

Mulit-stage Docker file: example

Here is the final Dockerfile:

FROM gcc:9.5.0 AS compiler
ADD https://raw.githubusercontent.com/docker-library/hello-world/master/hello.c  /hello.c
RUN make hello
FROM ubuntu
COPY --from=compiler /hello /hello
CMD /hello
Let's build it, and check that it works correctly: 
docker build -t hellomultistage .

and now we can test: 

docker run hellomultistage

Home work

List our images with docker images, and check the size of:

  • The ubuntu base image,

  • The single-stage hello image,

  • The multi-stage hellomultistage image.

We can achieve even smaller images if we use smaller base images ( i.e. Apline etc )