Fails on build with message "Are you trying to mount a directory onto a file (or vice-versa)?"

Build Environment
,
1

Hi,
I’m developing a web application with Flask+nginx+MySQL with docker-compose, and having a build and test problem on CircleCI.
CircleCI jobs keep failing with error messages like:

Error response from daemon: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error mounting “/home/circleci/xxx/nginx/nginx.conf” to rootfs at “/etc/nginx/nginx.conf”: mount /home/circleci/xxx/nginx/nginx.conf:/etc/nginx/nginx.conf (via /proc/self/fd/6), flags: 0x5000: not a directory: unknown: Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type

Environment

  • Windows 11
  • WSL2 Ubuntu 20.04.4
  • Docker Desktop 4.10.1
  • Docker Compose version v2.6.1
  • Docker version 20.10.17, build 100c701
  • docker-compose creates 3 containers: nginx, Flask, and MySQL.

The directry structure is like: (I omitted unrelevant files and directories)

.
├── app
│   └── Dockerfile
│   └── src/
├── docker-compose.yml
├── mysql
│   └── Dockerfile
└── nginx
    ├── Dockerfile
    └── log
        └── nginx/
    └── nginx.conf

docker-compose.yml is like:

version: '3'
services:
  db:
    ...

  flask:
    ...

  nginx:
    build: ./nginx/
    container_name: nginx
    ports:
      - '80:80'
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf
      - ./nginx/log/nginx:/var/log/nginx
    depends_on:
      - flask
    networks:
      - front
...

nginx/Dockerfile is like:

FROM nginx:1.17.9
CMD ["nginx", "-g", "daemon off;", "-c", "/etc/nginx/nginx.conf"]

and, .circleci/config.yml is like:

version: 2

jobs:
  build-and-test:
    working_directory: ~/xxx
    docker:
      - image: cimg/python:3.7.13

    steps:
      - checkout
      - run:
          name: Copy envfiles
          command: |
            echo $MYSQL_ENV | base64 -di > mysql/envfile
            echo $APP_ENV | base64 -di > app/src/tbl/.env
      - setup_remote_docker
      - run:
          name: Start all services declared in docker-compose.yml
          command: |
            set -x
            docker-compose up -d
      - run:
          working_directory: ~/xxx/app/src
          name: Test
          command: |
            docker-compose exec flask pytest

...

workflows:
  version: 2
  workflows:
    jobs:
      - build-and-test
      - deploy:
          requires:
            - build-and-test
          filters:
            branches:
              only: master

What I confirmed and tried

  • nginx/nginx.conf is definitely a file, and the target path /etc/nginx/nginx.conf is also a file. So none of them is a directory as the error message says.
  • Removed - ./nginx/nginx.conf:/etc/nginx/nginx.conf line in docker-compose.yml and added COPY nginx.conf /etc/nginx/nginx.conf line in nginx/Dockerfile. Build succeeded but nginx.conf was not copied to the container so the nginx server did not work properly.
  • And, that code does work in my local environment.

I am totally stack and I would appreciate any advice.

Thank you in advance.

2

This topic is solved thanks to CircleCI supports.
I’d like to share what I did.

The reason for the error is that I used a docker executor and remote docker which do NOT support volume mounting.
Instead, I used a machine executor. I have done two things in config.yml:

  • switched a docker executor to a machine executor
  build-and-test:
    working_directory: ~/xxx
    # docker:
    #  - image: cimg/python:3.7.13
    machine:
      image: ubuntu-2004:2022.10.1
  • removed setup_remote_docker line

Reference