gitlab-runner [runners.docker] 卷是如何工作的？

Question

根据文档，我配置运行器：

[[runners]]
  name = "docker-dind"
  url = "http://127.0.0.1/"
  token = "KhrzNHQc19_NME-WDgTW"
  executor = "docker"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]
    [runners.cache.azure]
  [runners.docker]
    tls_verify = false
    image = "docker:20.10.9"
    privileged = true
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["/certs/client", "/cache"]
    shm_size = 0

    [[runners.docker.services]]
      name = "docker:20.10.9-dind"

它工作正常，但我想知道它是如何工作的，服务 docker:dind 如何将“/certs/client”共享到作业图像 docker

# Specify to Docker where to create the certificates. Docker
  # creates them automatically on boot, and creates
  # `/certs/client` to share between the service and job
  # container, thanks to volume mount from config.toml