docker-compose.yml

version: "3"

networks:
    proxy: //thats the network from before
        external: true
    nextcloud: //thats a new seperate, unexposed network that only exists for nextcloud and its database
        external: false

volumes: #you can play around here. most people acctually create way more volumes but this workes out okay for me
    nextcloud:
    nextcloud-db:

services:
    nextcloud-db: #your mariadb database
        image: mariadb:10.4.1-bionic
        container_name: nextcloud-mariadb
        networks:
            - nextcloud //as you can see, the db only needs to be running in the internal network
        volumes:
            - nextcloud-db:/var/lib/mysql
            - /etc/localtime:/etc/localtime:ro
        environment: #replace those with something secure
            - MYSQL_ROOT_PASSWORD=rootpw
            - MYSQL_PASSWORD=mysql
            - MYSQL_DATABASE=nextcloud
            - MYSQL_USER=nextcloud
        restart: unless-stopped

    nextcloud:
        image: nextcloud:15.0.2-apache
        depends_on:
            - nextcloud-db
        restart: unless-stopped
        volumes:
            - nextcloud:/var/www/html
            - /data/nextcloud:/var/www/html/data #here is the data is stored
        labels: //those are the lables required for traefik to work and do its magic
            - traefik.enable=true
            - traefik.frontend.rule=Host:nextcloud.yourdomain.tld
            - traefik.docker.network=proxy
            - traefik.port=80
            - traefik.protocol=http
        networks:
            - nextcloud
            - proxy //also has to run in the external network that traefik uses