Do Dockerfiles need CMD/ENTRYPOINT?

Programming
,
1

The Docker documentation states that a CMD or ENTRYPOINT is required in order to successfully build an image, yet it is possible to build an image without either of these. The following example explains how to do this, using the Alpine tar as its base image:

FROM scratch
ADD alpine-minirootfs-3.11.2-x86_64.tar.gz /
COPY . /

To build the image, run:

docker build -t test:1 .

The image can then be run with no CMD or ENTRYPOINT:

docker run -ti test:1 /bin/sh

This demonstrates that it is possible to build a Docker image without either CMD or ENTRYPOINT.

2

The example provided shows that it is possible to build a Docker image without either CMD or ENTRYPOINT. The key is to use FROM scratch as the base image and then add the necessary files using ADD and COPY commands.