Docker CMD doesn't see installed components - docker

Question

I am trying to build a docker image using the following docker file.
FROM ubuntu:latest
# Replace shell with bash so we can source files
RUN rm /bin/sh && ln -s /bin/bash /bin/sh
# Update packages
RUN apt-get -y update && apt-get install -y \
curl \
build-essential \
libssl-dev \
git \
&& rm -rf /var/lib/apt/lists/*
ENV APP_NAME testapp
ENV NODE_VERSION 5.10
ENV SERVE_PORT 8080
ENV LIVE_RELOAD_PORT 8888
# Install nvm, node, and angular
RUN (curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.31.1/install.sh | bash -) \
&& source /root/.nvm/nvm.sh \
&& nvm install $NODE_VERSION \
&& npm install -g angular-cli \
&& ng new $APP_NAME \
&& cd $APP_NAME \
&& npm run postinstall
EXPOSE $SERVE_PORT $LIVE_RELOAD_PORT
WORKDIR $APP_NAME
EXPOSE 8080
CMD ["node", "-v"]
But I keep getting an error when trying to run it:
docker: Error response from daemon: Container command 'node' not found or does not exist..
I know node is being properly installed because if I rebuild the image by commenting out the CMD line from the docker file
#CMD ["node", "-v"]
And then start a shell session
docker run -it testimage
I can see that all my dependencies are there and return proper results
node -v
v5.10.1
.....
ng -v
angular-cli: 1.0.0-beta.5
node: 5.10.1
os: linux x64
So my question is. Why is the CMD in Dockerfile not able to run these and how can I fix it?

Answer 1

When using the shell to RUN node via nvm, you have sourced the nvm.sh file and it will have a $PATH variable set in it's environment to search for executable files via nvm.
When you run commands via docker run it will only inject a default PATH
docker run <your-ubuntu-image> echo $PATH
docker run <your-ubuntu-image> which node
docker run <your-ubuntu-image> nvm which node
Specifying a CMD with an array execs a binary directly without a shell or a $PATH to lookup.
Provide the full path to your node binary.
CMD ["/bin/node","-v"]
It's better to use the node binary rather than the nvm helper scripts due to the way dockers signal processing works. It might be easier to use the node apt packages in docker rather than nvm.