Run gitlab as a container

Run the container:
docker run -p 8000:80 gitlab/gitlab-ce

docker run -d \
  --name gitlab \
  --hostname localhost \
  -p 8000:80 -p 8443:443 -p 8022:22 \
  -v gitlab_config:/etc/gitlab \
  -v gitlab_logs:/var/log/gitlab \
  -v gitlab_data:/var/opt/gitlab \
  --shm-size 256m \
  gitlab/gitlab-ce:latest

Check the container running:
docker ps | grep gitlab-ce

Now check the root password to access gitlab:
docker exec -it IDCONTAINER cat /etc/gitlab/initial_root_password

Install a gitlab-runner:

curl -L "https://packages.gitlab.com/install/repositories/runner/gitlab-runner/script.deb.sh" | sudo bash

sudo apt install gitlab-runner 

Register the runner:
sudo gitlab-runner register

There you need to enter the gitlab instance, token and the executor.

For executor:

docker

For the image:
docker:20.10.16