• Using SSH private keys securely when building Docker images
• SSH Agent Forwarding with your Docker Container

None of these examples seemed to suit my use case or just didn’t seem to work.

So I decided to go back to the drawing board and figure this out myself. It turns out that it is actually quite simple. The documentation for this is pretty much the same as the standard docs you would find for creating SSH keys for github and adding them to the SSH agent. My use case was probably special — I had no intention of the build being triggered on a build server so I wasnt worried about accessing the SSH key and I only really wanted my SSH key to be used and also the docker build command was triggered from a yarn start command so I was able to do something special before the docker build process started.

My yarn start command started by triggering a shell file that copied my .ssh folder into the root of my project:

cp -r ~/.ssh .ssh

This got my ssh keys into my project so now it was just a matter of using these files as part of my docker build.

WORKDIR /tmp

COPY .ssh .ssh

WORKDIR /

RUN cp -r /tmp/.ssh ~/.ssh
RUN eval "$(ssh-agent -s)"

# do any other ssh dependant stuff you want

# clean things up
RUN rm -rf /tmp

So then on doing a docker build command I would have the ssh-agent at my disposal to do any SSH specific stuff that I wanted and then at the end of the build to be extra tidy and not have my ssh keys lying around in my project:

rm -rf .ssh

Like I said this work flow worked for my use case, which was using a docker container to contain a test environment for local testing — but every use case is different and this may not work for you. But in sharing this, I hope that it does and at least someone out there will find the useful.