docker: npm install on docker start

Question

I'd like to have some kind of "development docker image" in which npm install is executed every time I restart my Docker Container (becuase I don't want to build, push and pull the new dev image every day from my local machine to our Docker server). So I thought I could do sth. like this in my Dockerfile:

CMD npm install git+ssh://[email protected]/my/project.git#develop && npm start

Sadly, this doesn't work. The container stops immediately after docker start and I don't know why, because this works:

RUN npm install git+ssh://[email protected]/my/project.git#develop
CMD npm start

(Just for testing, that's of course not what I want to have). But maybe I have some wrong perception of CMD and someone could enlighten me?

Answer 1

Make your CMD point to a shell script.

CMD ["/my/path/to/entrypoint.sh"]

with that script being:

#!/bin/bash
npm install git+ssh://[email protected]/my/project.git#develop
npm start
# whatever else

I find this easier for a few reasons:

1. Inevitably these commands increase with more being done
2. It makes it much easier to run containers interactively, as you can run them with docker run mycontainer /bin/bash and then execute your shell script manually. This is helpful in debugging