COPY package.json - Dockerfile

Question

I did a Dockerfile to a project in Node.js but an error happened.

Here's the Dockerfile:

FROM node:latest
RUN npm install nodemon -g
WORKDIR ./app
COPY package.json ./app
RUN npm install -g
COPY server.js ./app
EXPOSE 3000
CMD ["npm", "start"] 

When I tried building this Dockerfile happen an error like this:

Step 4/8 : COPY package.json ./app
COPY failed: stat /var/lib/docker/tmp/docker-builderXXXXXXXX/package.json: no such file or directory

How can I fix it?

Docker version 17.12.0

Answer 1

Do not ever run nodemon in production (if that's what you tried to do). You should configure your restart in case if app crashes. Preferably, set it to always in docker-compose.yml

The best way to structure Dockerfile in your case:

FROM node:latest
WORKDIR ./app
# please note, you already declared a WORKDIR, 
# therefore your files will be automaticaly pushed to ./app
COPY package.json ./
RUN npm install -g
COPY ./ ./ 
EXPOSE 3000
CMD ["npm", "start"]

Hope, that helps.

Answer 2

Make sure you have package.json and server.js files in the same directory of your Dockerfile and it should work.

When you build a docker image, the whole content of the directory becomes your docker build context, and docker will find the files you COPY or ADD from there.

You might sometime wants to prevent some of those files to be sent to the build context, in which case you use the .dockerignore file to specify those files. Good luck!