reduce number of files

Dockerfile

@@ -12,7 +12,22 @@ COPY --from=download-gotty /go/bin/gotty /app/gotty
 RUN mkdir /lib64 && ln -s /lib/libc.musl-x86_64.so.1 /lib64/ld-linux-x86-64.so.2
 
 COPY start-shell.sh start-shell.sh
-COPY ChallengeDockerfile Dockerfile
+# create the same dockerfile for every challenge
+RUN <<EOF
+cat <<HEREDOC > Dockerfile
+# The basic dockerfile that is loaded for each console.
+# should take ~1MB per open console.
+FROM ubuntu:22.04 
+
+COPY SETUP.sh SETUP.sh
+RUN bash SETUP.sh
+RUN rm SETUP.sh
+
+CMD ["/bin/bash"]
+HEREDOC
+EOF
+
+# copy into image for setup (it will be deleted before the final image)
 COPY SETUP.sh SETUP.sh
 
 # run docker containers inside this docker container.