I have a python code and to convert it to docker image, I can use below command:

```
sudo docker build -t customdocker .

```

This converts python code to docker image. To convert it I use a Dockerfile with below commands:

```
FROM python:3

ADD my_script.py /

ADD user.conf /srv/config/conf.d/

RUN pip3 install <some-package>

CMD [ "python3", "./my_script.py" ]

```

In this, we have `RUN` command which install required packages. Lets say if we have deleted the image for some reason and want to build it again, so is there any way we can skip this `RUN` step to save some time because I think this is already installed.

Also in my code I am using a file `user.conf` which is in other directory. So for that I am including this in DOckerfile and also saving a copy of it in current directory. Is there a way in docker where I can define my working directory so that docker image searches for the file inside those directories.

Thanks