TIL - docker scratch image

TIL - Docker scratch image

TIL, Today I Learned, is more of a "I just figured this out: here are my notes, you may find them useful too" rather than a full blog post

The scratch image is the smallest possible image for docker. It does not contain any libraries nor other executables. It is simply a new, fresh and empty setup of namespaces.

The FROM scratch line is even a no-op [1] in the Dockerfile, which results in that it will not create an extra layer in you image. Example of a Dockerfile:

FROM scratch
ADD hello /
CMD ["/hello"]

As the Docker image does not contains any libraries, the hello application in the example above has to be compiled statically.

One use I see is to setup a Docker image based on a completely custom made root filesystem, e.g. the output from Buildroot.

See Docker documentation [2] for further reading.