working config

docker-compose.yml

version: '2'

services:
  rancher-ui:
    image: 'rancher/server'
    container_name: rancher-ui
    command: --advertise-address rancher --advertise-http-port 8080
    restart: always
    depends_on:
      - mariadb
    ports:
      - 8080:8080
      - 9345:9345
    environment:
      - VIRTUAL_HOST=rancher
      - VIRTUAL_PORT=8080
      - CATTLE_DB_CATTLE_MYSQL_HOST=mariadb
      - CATTLE_DB_CATTLE_MYSQL_PORT=3306
      - CATTLE_DB_CATTLE_MYSQL_NAME=cattle
      - CATTLE_DB_CATTLE_USERNAME=cattle
      - CATTLE_DB_CATTLE_PASSWORD=cattle

  nginx-proxy:
    image: 'jwilder/nginx-proxy'
    container_name: nginx-proxy
    restart: always
    ports:
      - 80:80
      - 443:443
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro

  mariadb:
    image: 'mariadb:latest'
    container_name: mariadb
    restart: always
    ports:
      - 3306
    volumes:
      - data-mariadb:/var/lib/mysql
    environment:
      - MYSQL_RANDOM_ROOT_PASSWORD=yes
      - MYSQL_USER=cattle
      - MYSQL_PASSWORD=cattle
      - MYSQL_DATABASE=cattle

volumes:
  data-mariadb:
    external: true