services:
  db:
    image: mariadb
    restart: always
    command: --transaction-isolation=READ-COMMITTED --log-bin=binlog --binlog-format=ROW
    volumes:
      - ./mysql:/var/lib/mysql
    environment:
      - MYSQL_PASSWORD=supersecretpassword
      - MYSQL_DATABASE=nextclouddb
      - MYSQL_USER=nextclouduser
      - MYSQL_RANDOM_ROOT_PASSWORD='yes'

  redis:

    image: redis

    restart: always

    command: redis-server --requirepass supersecretpassword2

  app:
    image: nextcloud:27
    restart: always
    ports:
      - 8080:80
    links:
      - db
      - redis
    volumes:
      - ./html:/var/www/html
    environment:
      - MYSQL_PASSWORD=supersecretpassword
      - MYSQL_DATABASE=nextclouddb
      - MYSQL_USER=nextclouduser
      - MYSQL_HOST=db
      - REDIS_HOST_PASSWORD=supersecretpassword2
    depends_on:
      - db
      - redis
  cron:
    image: nextcloud:27
    restart: always
    volumes:
      - ./html:/var/www/html
    entrypoint: /cron.sh
    depends_on:
      - db

To use this you need docker-compose installed. Once thats installed create a nextcloud folder and copy in this file as docker-compose.yaml. Once you are in the working directory run docker-compose up -d