Docker base cmds

[prakashpsgcse]

1. WORKDIR
2. adduser
3. set -ex;
4. ln
5. RUN apk add --no-cache openssh
6. ARG
7. RUN
8. VOLUME
9. EXPOSE
10. ENV
11. ARG
12. STOPSIGNAL
13. COPY
14. ENTRYPOINT
    15 .gracefully shutdown
    16 .build context
    17 mkdir -p
    18.HEALTHCHECK