Attaching to a docker container with base image scratch?

Question

I have a docker file as follows:

FROM scratch

ARG VERSION=NOT_SET
ENV VERSION $VERSION

COPY foobar foobar
COPY foobar-*.yaml /etc/
COPY jwt/ /etc/jwt/

EXPOSE 8082

ENTRYPOINT ["./foobar"]
CMD ["-config", "/etc/foobar-local.yaml"]

Now, docker ps shows the following:

CONTAINER ID        IMAGE                                                               COMMAND                  CREATED              STATUS              PORTS                         NAMES
653a9b287eb6        7693481.dkr.ecr.us-east-1.amazonaws.com/foobar:0.0.1           "./foobar -config /e"   About a minute ago   Up About a minute                                 foobar

When I try to exec to this container with the following command:

sudo docker exec -it 653a9b287eb6 /bin/bash

it shows the following error:

rpc error: code = 2 desc = oci runtime error: 
exec failed: exec: "/bin/bash": stat /bin/bash: no such file or directory

Answer 1

You need to add a shell to your empty base image (SCRATCH) in order to attach to it.

Right now, your image only include an executable, which is not enough.

As mentioned in issue 17896

FROM scratch literally is an empty, zero-byte image / filesystem, where you add everything yourself.
See for example, the hello-world which, produces an image that's 860 bytes total.

If you need a shell to attach to it through docker exec, start from a small image like Alpine (which has only /bin/sh though: you would need apk add bash to add bash, as commented below by user2915097).