Why did mysql data ownership change to systemd-jou

Question

I have the mysql database stored in /home/mysql instead of /var/lib/mysql. The directory used to be owned by mysql. However, when I run the command docker-compose up with this yml file:

version: '3'
services:
  mariadb:
    image: mariadb
    restart: always
    volumes:
     - /home/mysql:/var/lib/mysql
  elasticsearch:
    image: docker.elastic.co/elasticsearch/elasticsearch:5.6.4
    environment:
      - "ES_JAVA_OPTS=-Xms750m -Xmx750m"
      - bootstrap.memory_lock=false
  site:
    build: .
    volumes:
      - "./app:/app"
    links:
      - mariadb:mysql
    environment:
      - DOCKER_IP=172.19.0.2
    depends_on: ['elasticsearch','mariadb']
    ports:
      - "3000:3000"

The docker container is able to run, but the entire folder and files in /home/mysql are owned by systemd-journal-remote, which causes the node server fails to connect to mariadb. I have to stop the docker instance, restore the mysql folder ownership and delete ib_logfile0 and ib_logfile1.

Why does mounting /home/mysql cause such a fatal problem?

Update:

My solution is to add user: "mysql":

version: '3'
services:
  mariadb:
    image: mariadb
    restart: always
    volumes:
     - /home/mysql:/var/lib/mysql
    user: "mysql"
  elasticsearch:
    image: docker.elastic.co/elasticsearch/elasticsearch:5.6.4
    environment:
      - "ES_JAVA_OPTS=-Xms750m -Xmx750m"
      - bootstrap.memory_lock=false
  site:
    build: .
    volumes:
      - "./app:/app"
    links:
      - mariadb:mysql
    environment:
      - DOCKER_IP=172.19.0.2
    depends_on: ['elasticsearch','mariadb']
    ports:
      - "3000:3000"

Answer 1

You should start Docker's container with --user parameter. If you do this and set the same uid:gid as owner of the MySQL storage you will no have problems with permissions. You have to check how exactly to do this in Docker Compose because I show you example for normal command line execution

Answer 2

Most likely, uid of your user systemd-journal-remote is the same as uid of user mysqld in container. Check with ls -n. To avoid confusion, either use common uids, perhaps test as root:root with chmod o+rwx.