How to fix invalid ELF header error, on raspberry pi 3 running on Balena?

Question

I am trying to convert a Node.js application using the rpio library, to run on a Raspberry Pi 3 powered by Balena in local mode. In other words, I am looking to control GPIO's on the raspberry pi through Nodejs+Docker+Balena.

My Dockerfile installs gcc-4.8 support as mentioned as a dependency by the rpio library. The container is build without any problems. But when the node process starts it throws the error invalid ELF header :

17:50:00 - error: uncaughtException: /usr/src/app/node_modules/rpio/build/Release/rpio.node: invalid ELF header

To debug if the error was somehow related to the platform architecture, I added the command RUN uname -a both in the dockerfile and in the node's application code. The correspondingly return the following:

(Dockerfile)Linux 96cbf2e6ef3d 4.14.68 #1 SMP Tue Nov 27 09:53:28 UTC 2018 armv7l GNU/Linux
(Node file) Linux 2cfca32 4.14.68      #1 SMP Tue Nov 27 09:53:28 UTC 2018 armv7l GNU/Linux

I have a hard time figuring out what to do from here, since the architecture seems to match.

Dockerfile

FROM resin/raspberrypi3-node:8

# use apt-get if you need to install dependencies,
# for instance if you need ALSA sound utils, just uncomment the lines below.
RUN apt-get update && apt-get install -yq \
   alsa-utils libasound2-dev gcc-4.8 g++-4.8 && \
   apt-get clean && rm -rf /var/lib/apt/lists/*

RUN update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 50 && \
   update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 50

RUN gcc --version
# Defines our working directory in container
WORKDIR /usr/src/app

# Copies the package.json first for better cache on later pushes
COPY package.json package.json
# COPY package-lock.json package-lock.json

# This install npm dependencies on the balena build server,
# making sure to clean up the artifacts it creates in order to reduce the image size.
RUN JOBS=MAX npm install --production --unsafe-perm && rm -rf /tmp/*
RUN uname -a

# This will copy all files in our root to the working  directory in the container
COPY . ./

# Enable systemd init system in container
ENV INITSYSTEM on

# server.js will run when container starts up on the device
CMD ["npm", "start"]

package.json

"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "setup-log": "touch logs/app.log",
    "prestart": "bash ./deps.sh",
    "start": "npm run -s setup-log && node skaale/index.js"
},
"dependencies": {
  "cron": "^1.2.1",
  "firebase-admin": "^6.4.0",
  "moment": "^2.18.1",
  "request": "^2.88.0",
  "request-promise": "^4.2.0",
  "rimraf": "^2.6.2",
  "rpio": "^1.0.11",
  "winston": "^2.3.1",
  "winston-daily-rotate-file": "^1.4.6"
}

Full error stack

[ 'Error: /usr/src/app/node_modules/rpio/build/Release/rpio.node: invalid ELF header',
     '    at Object.Module._extensions..node (module.js:681:18)',
     '    at Module.load (module.js:565:32)',
     '    at tryModuleLoad (module.js:505:12)',
     '    at Function.Module._load (module.js:497:3)',
     '    at Module.require (module.js:596:17)',
     '    at require (internal/module.js:11:18)',
     '    at bindings (/usr/src/app/node_modules/bindings/bindings.js:81:44)',
     '    at Object.<anonymous> (/usr/src/app/node_modules/rpio/lib/rpio.js:17:34)',
     '    at Module._compile (module.js:652:30)',
     '    at Object.Module._extensions..js (module.js:663:10)',
     '    at Module.load (module.js:565:32)',
     '    at tryModuleLoad (module.js:505:12)',
     '    at Function.Module._load (module.js:497:3)',
     '    at Module.require (module.js:596:17)',
     '    at require (internal/module.js:11:18)',
     '    at Object.<anonymous> (/usr/src/app/utils/gpioHelper.js:5:12)',
     '    at Module._compile (module.js:652:30)',
     '    at Object.Module._extensions..js (module.js:663:10)',
     '    at Module.load (module.js:565:32)',
     '    at tryModuleLoad (module.js:505:12)',
     '    at Function.Module._load (module.js:497:3)',
     '    at Module.require (module.js:596:17)' ] }

Answer 1

I believe the issue is that the node module needs to be created on the host machine. Because you are running in docker, you need to ignore your outdated node_modules so that the rpio module is created on the fly since it depends on hardware. All I had to do to fix this is add a.dockerignore with 'node_modules' and it compiled correctly.

Not sure how copying package-lock.json affects this.

Hope it helps,

Answer 2

If you are running inside a docker container as I am, all you need is a .dockerignore with 'node_modules' specified in it.

Some libraries need to be compiled on the host machine and therefore your modules can be stale.