Dockerfile: $HOME is not working with ADD/COPY instructions

Question

Before filing a bug I would like to ask someone to confirm the weird docker build behavior I have recently faced with.

Consider we have a simple Docker

Answer 1

Here's your problem:

When you use the USER directive, it affects the userid used to start new commands inside the container. So, for example, if you do this:

FROM ubuntu:utopic
RUN useradd -m aptly
USER aptly
RUN echo $HOME

You get this:

Step 4 : RUN echo $HOME
 ---> Running in a5111bedf057
/home/aptly

Because the RUN commands starts a new shell inside a container, which is modified by the preceding USER directive.

When you use the COPY directive, you are not starting a process inside the container, and Docker has no way of knowing what (if any) environment variables would be exposed by a shell.

Your best bet is to either set ENV HOME /home/aptly in your Dockerfile, which will work, or stage your files into a temporary location and then:

RUN cp /skeleton/myfile $HOME/myfile

Also, remember that when you COPY files in they will be owned by root; you will need to explicitly chown them to the appropriate user.