To export the files of a container, use the command "docker export".

Let's create a container and export its contents:
$ docker export $(docker create hello-world) | tar -tv -rwxr-xr-x 0/0 0 .dockerenv drwxr-xr-x 0/0 0 dev/ -rwxr-xr-x 0/0 0 dev/console drwxr-xr-x 0/0 0 dev/pts/ drwxr-xr-x 0/0 0 dev/shm/ drwxr-xr-x 0/0 0 etc/ -rwxr-xr-x 0/0 0 etc/hostname -rwxr-xr-x 0/0 0 etc/hosts lrwxrwxrwx 0/0 0 etc/mtab -> /proc/mounts -rwxr-xr-x 0/0 0 etc/resolv.conf -rwxrwxr-x 0/0 13336 hello drwxr-xr-x 0/0 0 proc/ drwxr-xr-x 0/0 0 sys/
If you check at the Dockerfile of the "hello-world" image (see bellow), you will notice that it only copy the "hello" file which is the only non-empty file in the container.

The other files and directories in the container are mandatory and Docker will automatically bind-mount them from the Docker host.

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