Why use docker and docker dind for docker tasks?

GitLab CI/CD
, ,
1

Hello,
I have question regarding CI tasks with docker containers.
Take a look a the following task. This is what I found common when building a docker image and push it to a registry.

image_build:
  stage: release
  image:
    name: docker:19.03.1
  variables:
    DOCKER_TLS_CERTDIR: "/certs"
  services: 
    - name: docker:19.03.1-dind
      # alias: docker
  script:
    - docker info
...

What i do not understand: Why use a docker image paired with a docker-in-docker service? Why not just use a docker-in-docker image?

Also, has anyone managed to get this working. For some reason I cant reach the dind socket from the docker container even though they are on the same network. The task fails with this error:

$ docker info
error during connect: Get https://docker:2376/v1.39/info: dial tcp: lookup docker on 127.0.0.11:53: no such host
ERROR: Job failed: exit code 1

Here is my runner config.toml

concurrent = 1
check_interval = 0

[session_server]
  session_timeout = 1800

[[runners]]
  name = "Gitlab runner for Kubernetes ops"
  url = "http://gitlab"
  token = "k9hqyTbyMgyS4wck7aqo"
  executor = "docker"
  pre_clone_script = "git config --global http.sslCAInfo /etc/ssl/certs/myCA.crt"
  tls-ca-file = "/etc/gitlab-runner/certs/myCA.crt"
  [runners.custom_build_dir]
  [runners.docker]
    tls_verify = false
    image = "ruby:2.6"
    privileged = false
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["/certs/client", "/cache", "/home/yacine/Documents/kube-gitlab-cicd/ca/myCA.pem:/etc/ssl/certs/myCA.crt"]
    shm_size = 0
    network_mode = "traefik"
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]

Is this related to the MR 1569?