docker executable file not found in $PATH

Question

Trying to run a rails migration on a running docker compose container throws this error:

$ docker-compose run webapp rails db:migrate

ERROR: Cannot start service webapp: invalid header field value "oci runtime error: container_linux.go:247: starting container process caused \"exec: \\"rails\\": executable file not found in $PATH\"\n"

However, I can access rails from inside the container:

$ docker-compose run webapp bash
root@3fd3a87275a1:/home/app/webapp# which rails
/usr/local/rvm/gems/ruby-2.3.1/bin/rails

My container is already running and I can GET the page:

$ curl http://localhost -i
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Status: 200 OK
Cache-Control: max-age=0, private, must-revalidate
ETag: W/"b62d4f67b7b823c017534cd9727752cd"
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-Runtime: 0.019881
X-Request-Id: eb32ec21-3a8f-4caa-a27b-2e42f0b2bce9
Date: Thu, 15 Dec 2016 15:15:59 GMT
X-Powered-By: Phusion Passenger 5.0.29
Server: nginx/1.10.1 + Phusion Passenger 5.0.29

How do I run rails db:migrate in my container?

Dockerfile

FROM phusion/passenger-ruby23

# Set correct environment variables.
ENV HOME /root

# Use baseimage-docker's init process.
CMD ["/sbin/my_init"]

# additional packages
RUN apt-get update

# Active nginx
RUN rm -f /etc/service/nginx/down

# Install bundle of gems
WORKDIR /tmp
ADD Gemfile /tmp/
ADD Gemfile.lock /tmp/
RUN bundle install

# Copy the nginx template for configuration and preserve environment variables
RUN rm /etc/nginx/sites-enabled/default

# Add the nginx site and config
ADD webapp.conf /etc/nginx/sites-enabled/webapp.conf

RUN mkdir /home/app/webapp
COPY . /home/app/webapp
RUN usermod -u 1000 app
RUN chown -R app:app /home/app/webapp
WORKDIR /home/app/webapp

# Clean up APT when done.
RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
EXPOSE 80

Docker Compose

version: '2'
services:
  webapp:
    build: .
    container_name: myapp
    working_dir: /home/app/webapp
    ports:
      - "80:80"
    environment:
      - PASSENGER_APP_ENV=development
    volumes:
      - .:/home/app/webapp
    networks:
      - back-end
  db:
    container_name: db
    image: postgres:9.4
    networks:
      - back-end
networks:
  back-end:
    driver: bridge

Answer 1

I don't know why this is happening, and I've filed an issue, but in the meantime, here's a workaround:

docker-compose run webapp bundle exec rails db:migrate

Please answer this question with a proper fix, and I'll accept your answer.