GitLab CI runner can't connect to unix:///var/run/docker.sock in kubernetes

Question

GitLab's running in kubernetes cluster. Runner can't build docker image with build artifacts. I've already tried several approaches to fix this, but no luck. Here are some configs snippets:

.gitlab-ci.yml

image: docker:latest
services:
  - docker:dind

variables:
  DOCKER_DRIVER: overlay

stages:
  - build
  - package
  - deploy

maven-build:
  image: maven:3-jdk-8
  stage: build
  script: "mvn package -B --settings settings.xml"
  artifacts:
    paths:
      - target/*.jar

docker-build:
  stage: package
  script:
  - docker build -t gitlab.my.com/group/app .
  - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN gitlab.my.com/group/app
  - docker push gitlab.my.com/group/app

config.toml

concurrent = 1
check_interval = 0

[[runners]]
  name = "app"
  url = "https://gitlab.my.com/ci"
  token = "xxxxxxxx"
  executor = "kubernetes"
  [runners.kubernetes]
    privileged = true
    disable_cache = true

Package stage log:

running with gitlab-ci-multi-runner 1.11.1 (a67a225)
  on app runner (6265c5)
Using Kubernetes namespace: default
Using Kubernetes executor with image docker:latest ...
Waiting for pod default/runner-6265c5-project-4-concurrent-0h9lg9 to be running, status is Pending
Waiting for pod default/runner-6265c5-project-4-concurrent-0h9lg9 to be running, status is Pending
Running on runner-6265c5-project-4-concurrent-0h9lg9 via gitlab-runner-3748496643-k31tf...
Cloning repository...
Cloning into '/group/app'...
Checking out 10d5a680 as master...
Skipping Git submodules setup
Downloading artifacts for maven-build (61)...
Downloading artifacts from coordinator... ok        id=61 responseStatus=200 OK token=ciihgfd3W
$ docker build -t gitlab.my.com/group/app .
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
ERROR: Job failed: error executing remote command: command terminated with non-zero exit code: Error executing in Docker Container: 1

What am I doing wrong?

Answer 1

Don't need to use this:

DOCKER_DRIVER: overlay

cause it seems like OVERLAY isn't supported, so svc-0 container is unable to start with it:

$ kubectl logs -f `kubectl get pod |awk '/^runner/{print $1}'` -c svc-0
time="2017-03-20T11:19:01.954769661Z" level=warning msg="[!] DON'T BIND ON ANY IP ADDRESS WITHOUT setting -tlsverify IF YOU DON'T KNOW WHAT YOU'RE DOING [!]"
time="2017-03-20T11:19:01.955720778Z" level=info msg="libcontainerd: new containerd process, pid: 20"
time="2017-03-20T11:19:02.958659668Z" level=error msg="'overlay' not found as a supported filesystem on this host. Please ensure kernel is new enough and has overlay support loaded."

Also, add export DOCKER_HOST="tcp://localhost:2375" to the docker-build:

 docker-build:
  stage: package
  script:
  - export DOCKER_HOST="tcp://localhost:2375"
  - docker build -t gitlab.my.com/group/app .
  - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN gitlab.my.com/group/app
  - docker push gitlab.my.com/group/app