Docker-compose set user and group on mounted volume

Question

I'm trying to mount a volume in docker-compose to apache image. The problem is, that apache in my docker is run under www-data:www-data but the mounted directory is created under root:root. How can I specify the user of the mounted directory?

I tried to run command setupApacheRights.sh. chown -R www-data:www-data /var/www but it says chown: changing ownership of '/var/www/somefile': Permission denied

services:     httpd:         image: apache-image         ports:             - "80:80"         volumes:             - "./:/var/www/app"         links:             - redis         command: /setupApacheRights.sh 

I would prefer to be able to specify the user under which it will be mounted. Is there a way?

Answer 1

To achieve the desired behavior without changing owner / permissions on the host system do the following steps.

1. get the ID of the desired user and or group you want the permissions to match with executing the id command on your host system - this will show you the uid and gid of your current user and as well all IDs from all groups the user is in.

    $ id 

2. add the definition to your docker-compose.yml

    user: "${UID}:${GID}" 

   so your file could look like this

    php: # this is my service name      user: "${UID}:${GID}" # we added this line to get a specific user / group id      image: php:7.3-fpm-alpine # this is my image  # and so on 

3. set the values in your .env file

    UID=1000  GID=1001 

Now your user in the container has the id 1000 and the group is 1001 and you can set that differently for every environment.

Note: Please replace the IDs I used with the user / group IDs you found on your host system. Since I cannot know which IDs your system is using I gave some example group and user IDs.

If you don't use docker-compose or want to know more different approaches to achieve this have a read through my source of information: https://dev.to/acro5piano/specifying-user-and-group-in-docker-i2e

Answer 2

The bad news is there's no owner/group/permission settings for volume 😢. The good news is the following trick will let you bake it into your config, so it's fully automated 🎉.

In your Dockerfile, create an empty directory in the right location and with desired settings.

This way, the directory will already be present when docker-compose mounts to the location. When the server mounts during boot (based on docker-compose), the mounting action happily leaves those permissions alone.

Dockerfile:

# setup folder before switching to user RUN mkdir /volume_data RUN chown postgres:postgres /volume_data USER postgres 

docker-compose.yml

volumes:    - /home/me/postgres_data:/volume_data 

source