I will run docker on a dedicated sever by a service provider. It is not
possible to install docker on this server. Apache, Git and a lot more is
installed. So I try to run docker in a container. I will pull a docker image
from the gitlab registry and run in a sub domain. I wrote a .gitlab-ci.yml. But
I get an error message. 

I found [this answer](https://stackoverflow.com/a/51858399/10008173):

> 
> You can't (\*) run Docker inside Docker containers or images. You can't (\*)
>  start background services inside a Dockerfile. As you say, commands like
>  systemctl and service don't (\*) work inside Docker anywhere. And in any case
>  you can't use any host-system resources, including the host's Docker socket,
>  from anywhere in a Dockerfile.
> 
> 
> 

How do I solve this problem?

```
$ sudo docker run hello-world
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.
ERROR: Job failed: exit code 1

```

.gitlab-ci.yml

```
image: ubuntu:latest

before_script:
  - apt-get update
  - apt-get install -y apt-transport-https ca-certificates curl software-properties-common

  - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add
  - apt-key fingerprint 0EBFCD88
  - add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

stages:
    - test

test:
  stage: test
  script:
    - apt-get update
    - apt-cache search docker-ce
    - apt-get install -y docker-ce
    - docker run -d hello-world

```