Docker builds (dind)

How to Use GitLab
1

Hi,
Im trying to understand, how do i properly setup dind builds.
Here is my .gitlab-ci.yml

image: docker:latest
services:
   - docker:dind

variables:
  DOCKER_HOST: tcp://docker:2375/
  DOCKER_DRIVER: overlay2

before_script:  
  - apk update
  - apk add jq bash curl git
  - jq --version

main:  
  script:
    - ./build.sh

I have not registered any runner using gitlab utility as described here https://docs.gitlab.com/ee/ci/docker/using_docker_build.html, but it seem to just work.