docker ubuntu 中的 nodejs 找不到模块 /usr/src/app/index.js

Question

I'm trying to deploy an application I wrote to my unraid server so I had to docker-ize it. It's written with nodejs and depends on imagemagick and ghostscript so I had to include a build step to install those dependencies. I'm seeing an error when running this image though

Here's my dockerfile

FROM node
RUN mkdir -p /usr/src/app
RUN chmod -R 777 /usr/src/app
WORKDIR /usr/src/app
COPY . /usr/src/app
RUN npm i --only=production
FROM ubuntu
RUN apt-get update
RUN apt-get install -y imagemagick ghostscript nodejs
ENTRYPOINT node /usr/src/app/index.js

Console output

internal/modules/cjs/loader.js:638
throw err;
^

Error: Cannot find module '/usr/src/app/index.js'

at Function.Module._resolveFilename (internal/modules/cjs/loader.js:636:15)
at Function.Module._load (internal/modules/cjs/loader.js:562:25)
at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
at startup (internal/bootstrap/node.js:283:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)

Originally, my entrypoint was configured like ENTRYPOINT node./index.js but I thought that I was in the wrong directory or something but switching to an absolute path didn't work either so here I am.

Answer 1

By using a second from instruction, you are instrucing a second stage. Nothing from the first stage is availble to the second stage by default. If you need some artifacts you need to copy them explicitly.

FROM node as build
RUN mkdir -p /usr/src/app
RUN chmod -R 777 /usr/src/app
WORKDIR /usr/src/app
COPY . /usr/src/app
RUN npm i --only=production

# this is a new stage
FROM ubuntu
RUN apt-get update
RUN apt-get install -y imagemagick ghostscript nodejs
# you need to copy the things you need 
COPY --from=builder /usr/src/app /usr/src/app
ENTRYPOINT node /usr/src/app/index.js

That said, it seems pointless for a node app to do that. I would suggest using a single stage. The node runtime is required to run your app. Multi staging would make sense if you were to use node to build statics with something like webpack and then copy the produced statics into a second stage that doesn't need the node runtime.