Dockerfile/npm: create a sudo user to run npm install - node.js

Question

Creating a Dockerfile to install a node framework that we've created (per my earlier post here):
# Install dependencies and nodejs
RUN apt-get update
RUN apt-get install -y python-software-properties python g++ make
RUN add-apt-repository ppa:chris-lea/node.js
RUN apt-get update
RUN apt-get install -y nodejs
# Install git
RUN apt-get install -y git
# Bundle app source
ADD . /src
# Create a nonroot user, and switch to it
RUN /usr/sbin/useradd --create-home --home-dir /usr/local/nonroot --shell /bin/bash nonroot
RUN /usr/sbin/adduser nonroot sudo
RUN chown -R nonroot /usr/local/
RUN chown -R nonroot /usr/lib/
RUN chown -R nonroot /usr/bin/
RUN chown -R nonroot /src
USER nonroot
# Install app source
RUN cd /src; npm install
The problem is that npm expects to be run not as root -- is there a way to chain a series of sudo useradd commands to create a temp user that has sudo privileges that I can then switch to USER to run the npm install?
EDIT: updated the above, now getting this issue after successfuly creating a user and getting to the npm install line and choking:
Error: Attempt to unlock javascript-brunch#1.7.1, which hasn't been locked
at unlock (/usr/lib/node_modules/npm/lib/cache.js:1304:11)
at cb (/usr/lib/node_modules/npm/lib/cache.js:646:5)
at /usr/lib/node_modules/npm/lib/cache.js:655:20
at /usr/lib/node_modules/npm/lib/cache.js:1282:20
at afterMkdir (/usr/lib/node_modules/npm/lib/cache.js:1013:14)
at /usr/lib/node_modules/npm/node_modules/mkdirp/index.js:37:53
at Object.oncomplete (fs.js:107:15)
If you need help, you may report this *entire* log,
including the npm and node versions, at:
<http://github.com/npm/npm/issues>

Answer 1

The "Attempt to unlock" issue is often caused by not having the environment variable HOME set properly. npm needs this to be set to a directory that it can edit (it sets up and manages an .npm directory there).
You can specify environment variables in your docker run call with e. g. docker run -e "HOME=/home/docker".

Answer 2

To solve your "Attempt to unlock" issue, try cleaning the npm cache first by issuing
npm cache clean
After that, run
npm install

Answer 3

I came across a similar npm install error when I was trying to execute is as a non-root user in my Dockerfile. Svante's explanation of the issue is bang on, npm does some caching under the $HOME dir. Here's a simple Dockerfile that works with npm install:
FROM dockerfile/nodejs
# Assumes you have a package.json in the current dir
ADD . /src
# Create a nonroot user, and switch to it
RUN /usr/sbin/useradd --create-home --home-dir /usr/local/nonroot --shell /bin/bash nonroot
RUN chown -R nonroot /src
# Switch to our nonroot user
USER nonroot
# Set the HOME var, npm install gets angry if it can't write to the HOME dir,
# which will be /root at this point
ENV HOME /usr/local/nonroot
# Install app source
WORKDIR /src
RUN npm install