lalyos/scratch-chmx repository overview

Once you have static binaries you want to create the smallest possible docker container.

Requirements:

• automated/trusted build: so you have to put your Dockerfile into github
• a minimal docker image, so even alpine or busybox is big (compared to your binry which is probably under 1MB)
• don’t store the binary redundantly in github near to the Dockerfile

This Docker image is my proposed solution.

⁠Usage

FROM lalyos/scratch-chmx
ADD https://bintray.com/yourpackage/v1.2.3/mycli /bin/mycli
RUN ["/bin/chmx", "/bin/mycli"]

ENTRYPOINT ["/bin/mycli"]

⁠tl;dr

The plan is to create scratch based docker images with single static binaries. For example i want to dockerize upx⁠

⁠debian package

if you install it on top of debian:jessie

apt-get update && apt-get install -y upx

You end up with an image over 130 MB.

⁠alpine

You can use alpine as a base. But unfortunately there is no official upx package. With some work, you can build a static version of upx around 500KB. If you put into alpine, its again over 5MB

⁠scratch

If you put it into scratch, well it remains 500KB. The usual way to create a scratch base docker images:

FROM scratch
ADD upx /upx

But this way if you want an automated/trusted docker hub build, you have to put the binary into the git repo. Which shouldn’t be there.

So now the final Dockerfile should look like:

FROM scratch
ADD https://bintray.com/lalyos/upx/v1.2.3/upx /upx
RUN chmod +x /upx

But if you start from scratch there is no chmod ?!

⁠lalyos/scratch-chmx

This can be solved by adding a small tool which is written in C and can perform a chmod +x. Static compiled chmx is about: 88KB.

Of course its dockerized as:

FROM scratch
ADD chmx /bin/chmx

Now you can create an upx container as:

FROM lalyos/scratch-chmx