Docker persisted volum has no permissions (Apache Solr)

Question

My docker-compose.yml:

solr:
    image: solr:8.6.2
    container_name: myproject-solr
    ports:
     - "8983:8983"
    volumes:
      - ./data/solr:/var/solr/data
    networks:
      static-network:
        ipv4_address: 172.20.1.42

After bringing up the docker with docker-compose up -d --build, the solr container is down and the log (docker logs myproject-solr) shows this:

Copying solr.xml
cp: cannot create regular file '/var/solr/data/solr.xml': Permission denied

I've noticed that if I give full permissions on my machine to the data directory sudo chmod 777 ./data/solr/ -R and I run the Docker again, everything is fine.

I guess the issue comes when the solr user is not my machine, because Docker creates the data/solr folder with root:root. Having my ./data folder gitignored, I cannot manage these folder permissions.

I'd like to know a workaround to manage permissions properly with the purpose of persisting data

Answer 1

It's a known "issue" with docker-compose: all files created by Docker engine are owned by root:root. Usually it's solved in one of the two ways:

1. Create the volume in advance. In your case, you can create the ./data/solr directory in advance, with appropriate permissions. You might make it accessible to anyone, or, better, change its owner to the solr user. The solr user and group ids are hardcoded inside the solr image: 8983 (Dockerfile.template)

mkdir -p ./data/solr
sudo chown 8983:8983 ./data/solr

2. If you want to avoid running additional commands before docker-compose, you can create additional container which will fix the permissions:

version: "3"

services:

  initializer:
    image: alpine
    container_name: solr-initializer
    restart: "no"
    entrypoint: |
      /bin/sh -c "chown 8983:8983 /solr"
    volumes:
      - ./data/solr:/solr
    
  solr:
    depends_on: 
      - initializer
    image: solr:8.6.2
    container_name: myproject-solr
    ports:
     - "8983:8983"
    volumes:
      - ./data/solr:/var/solr/data  
    networks:
      static-network:
        ipv4_address: 172.20.1.42