Obtain your registration token by following these steps: https://docs.gitea.com/usage/actions/act-runner#obtain-a-registration-token

local-gitea-instance--docker-compose.yml

networks:
  gitea:
    external: false

services:
  server:
    image: docker.gitea.com/gitea:1.25.3
    container_name: gitea
    environment:
      - USER_UID=1000
      - USER_GID=1000
      - GITEA__database__DB_TYPE=mysql
      - GITEA__database__HOST=db:3306
      - GITEA__database__NAME=gitea
      - GITEA__database__USER=gitea
      - GITEA__database__PASSWD=gitea
    restart: always
    networks:
      - gitea
    volumes:
      - ~/.gitea-data/server:/data
      - /etc/timezone:/etc/timezone:ro
      - /etc/localtime:/etc/localtime:ro
    ports:
      - "3333:3000"
      - "22:22"
    depends_on:
      - db

  db:
    image: docker.io/library/mysql:8
    restart: always
    environment:
      - MYSQL_ROOT_PASSWORD=gitea
      - MYSQL_USER=gitea
      - MYSQL_PASSWORD=gitea
      - MYSQL_DATABASE=gitea
    networks:
      - gitea
    volumes:
      - ~/.gitea-data/db:/var/lib/mysql

  runner01:
    image: docker.io/gitea/act_runner:0.2.13
    environment:
      GITEA_INSTANCE_URL: "http://server:3000"
      GITEA_RUNNER_REGISTRATION_TOKEN: "<your_token_here>"
      GITEA_RUNNER_NAME: "runner01"
      GITEA_RUNNER_LABELS: "ubuntu-latest"
    volumes:
      - ~/.gitea-data/runner01:/data
      - /var/run/docker.sock:/var/run/docker.sock
    depends_on:
      - server
    restart: always
    networks:
      - gitea

  runner02:
    image: docker.io/gitea/act_runner:0.2.13
    environment:
      GITEA_INSTANCE_URL: "http://server:3000"
      GITEA_RUNNER_REGISTRATION_TOKEN: "<your_token_here>"
      GITEA_RUNNER_NAME: "runner02"
      GITEA_RUNNER_LABELS: "ubuntu-latest"
    volumes:
      - ~/.gitea-data/runner02:/data
      - /var/run/docker.sock:/var/run/docker.sock
    depends_on:
      - server
    restart: always
    networks:
      - gitea