can not run docker latest on gitlab-ci runner - docker

Question

I'm testing gitlab-ci and trying to generate an image on the registry from the Dockerfile.
I have the same code just to test:
#gitlab-ci
image: docker:latest
tages:
- build
- deploy
build_application:
stage: build
script:
- docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
- docker build -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA . -f Dockerfile
- docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA-test
output:
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
docker is running the image is being pulled but I can not execute docker commands.
In my local environment if a run:
docker run -it docker:latest
I stay inside the container and run docker info i have the same problem. I had to fix it by running the container on this way:
docker run -it --rm -v /var/run/docker.sock:/var/run/docker.sock docker:latest
but I do not know how to fix it on gitlab-ci. I configured my runner so:
docker run -d --name gitlab-runner --restart always \
-v /srv/gitlab-runner/config:/etc/gitlab-runner \
-v /var/run/docker.sock:/var/run/docker.sock \
gitlab/gitlab-runner:latest
Maybe someone can put me in the right direction.
thanks

Answer 1

By default it is not possible to run docker-in-docker (DIND) (as a security measure).
This section in the Gitlab docs is your solution. You must use Docker-in-Docker.
After configuring your runner to use DIND your .gitlab-ci.yml will look like this:
#gitlab-ci
image: docker:latest
variables:
DOCKER_DRIVER: overlay2
services:
- docker:dind
before_script:
- docker info
stages:
- build
- deploy
build_application:
stage: build
script:
- docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
- docker build -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA . -f Dockerfile
- docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA-test