Unable to mount a file with docker-compose

Question

I run docker-compose -f docker-compose.prod.yml up and I immediately get the error:

ERROR: for frontend  Cannot start service frontend: OCI runtime create failed: container_linux.go:348: starting container process caused "process_linux.go:402: container init caused \"rootfs_linux.go:58: mounting \\\"/c/Users/James/Projects/mysite/frontend/conf/nginx/mysite.template\\\" to rootfs \\\"/var/lib/docker/aufs/mnt/e7a2a699ae3e9ede0dd60b7cfdebb7f2d3adf71e8175157f3c9e88d3285796d2\\\" at \\\"/var/lib/docker/aufs/mnt/e7a2a699ae3e9ede0dd60b7cfdebb7f2d3adf71e8175157f3c9e88d3285796d2/etc/nginx/conf.d/default.conf\\\" caused \\\"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

My mysite.template file exists. I am using digital ocean with docker-machine. In development I didn't have this issue running on the same OS (ubuntu 16). I use docker toolbox on windows for development.

Here's the frontend config from docker-compose.prod.yml:

frontend:
image: nginx:stable-alpine
restart: always
networks:
  - web
  - default
volumes:
  - ${PWD}/frontend/conf/nginx/mysite.template:/etc/nginx/conf.d/default.conf
  - ${PWD}/frontend/public:/var/www/html
labels:
  - "traefik.enable=true"
  - "traefik.basic.frontend.rule=Host:mysite.com"
  - "traefik.basic.port=80"

I followed the instructions from the docs. Any ideas what's going wrong?

Solution

You can only mount host directories as volumes, and not individual files in Docker.

In your volumes definition, instead of this: - ${PWD}/frontend/conf/nginx/mysite.template:/etc/nginx/conf.d/default.conf

you should do this: - ${PWD}/frontend/conf/nginx:/etc/nginx/conf.d

Comments

[BugHunterUK]

This worked. Thank you. Does ${PWD}/frontend/public:/var/www/html put the contents of public/ into html/? A little confusing.

[Alex]

Thank you - i wasted so many hours trying to solve this. Your directory vs file point is vital in order to get this working correctly.