/bin/sh: my_custom command not found inside Docker container

Question

The context is the following: I need to run ffmpeg in a AWS Lambda service that is deployed and build using Docker. Since the docker image we use is not debian and does not includes ffmpeg, I created a binary file with the command and added it to the project files. Then, inside the Dockerfile, I create a link to these binary so the command is included in /bin.

This is the Dockerfile:

FROM lambci/lambda:build-nodejs6.10


# Create app directory
WORKDIR /app

# Install app dependencies
COPY package.json .
COPY yarn.lock .

#add ffmpeg files
COPY binaries .binaries

#make link to ffmpeg
RUN  ln -s /app/.binaries/bin/ffmpeg /bin/ffmpeg

RUN npm install --global yarn
RUN yarn install
RUN yarn global add serverless@~1.24.1

# Bundle app source
COPY . .

EXPOSE 8080
CMD [ "yarn", "run", "deploy" ]

Although this seems to be working in local environment (the command responds when called from console inside docker's image), it does not work when deployed to stage:

/bin/sh: ffmpeg: command not found

Answer 1

I recommend replacing CMD [ "yarn", "run", "deploy" ]

with

ENTRYPOINT ["sh", "/app/.binaries/yarn"]
CMD ["run", "deploy"]

I think you have 2 problems:

1. Do you know that yarn is executable? I don't know it is not, but explicitly calling sh means that it does not matter.
2. I don't think yarn is in the path. Explicitly using the absolute path of yarn means it should not matter.