add sudo user docker code example

Example: docker sudo how to add user

FROM alpine:latest
RUN apk --no-cache update \
    && apk --no-cache add sudo
copy run.sh /usr/local/
RUN addgroup -S cassandra && adduser -S cassandra -G cassandra
RUN chown -R cassandra:cassandra /home/cassandra/
RUN echo 'cassandra  ALL=(ALL) /bin/su' >>  /etc/sudoers
USER cassandra
ENTRYPOINT [ "sh","/usr/local/run.sh"]