GitLab本地Runner无法连接Docker守护进程问题求助

我在使用本地GitLab Runner时遇到无法连接Docker守护进程的问题，给Docker服务添加别名后仍失败，报错信息如下：

ERROR: Cannot connect to the Docker daemon at tcp://docker:2375/. Is the docker daemon running?
ERROR: Cannot connect to the Docker daemon at tcp://thealias:2375/. Is the docker daemon running?

我的配置文件 #

.gitlab-ci.yml #

push_image:
  image: docker:20.10.16-dind

  services:
    - docker:20.10.16-dind

  before_script:
    - docker info
    - docker login ext_registry.com -u $NEXUS_USER -p $NEXUS_PASS
  script:
    - docker build -t ext_registry.com.liberty.edu:5000/occ/groupsyncer:latest .

gitlab-runner.toml #

[[runners]]
  name = "docker-runner"
  url = "https://gitlab.example.com/"
  token = REDACTED
  executor = "docker"
  cache_dir="/cache"
  clone_url = "https://gitlab.example.com"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]
    [runners.cache.azure]
  [runners.docker]
    volumes = ["/opt/gitlab-runner/cache:/cache:rw"]
    tls_verify = false
    image = "docker:20.10.16"
    privileged = true
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    shm_size = 0

解决方法 #

1. 修正.gitlab-ci.yml配置
   不要同时将docker:dind作为job镜像和服务使用，应该用普通的docker镜像作为job运行环境，docker:dind作为后台服务。同时显式设置Docker环境变量避免连接问题：

   push_image:
     image: docker:20.10.16
     services:
       - name: docker:20.10.16-dind
         alias: docker
     variables:
       DOCKER_HOST: tcp://docker:2375
       DOCKER_TLS_CERTDIR: ""
     before_script:
       - docker info
       - docker login ext_registry.com -u $NEXUS_USER -p $NEXUS_PASS
     script:
       - docker build -t ext_registry.com.liberty.edu:5000/occ/groupsyncer:latest .
   

2. 确认Runner配置有效性
   你的gitlab-runner.toml中已经设置了privileged = true，这是docker:dind运行的必要条件。修改配置后重启Runner服务：

   gitlab-runner restart
   

3. 检查主机Docker服务状态
   在GitLab Runner所在主机上，确认Docker守护进程正在运行：

   systemctl status docker
   

   若未运行，启动服务：

   systemctl start docker
   

内容的提问来源于stack exchange，提问作者Brandon Kauffman