How to install and connect a gitlab runner

What’s a gitlab runner and what do I need it for?

gitlab runners are worker nodes that can be connected to gitlab to run jobs on.
I use the docker executor a lot to build images, but you can run any sort of jobs on them like shell/$language scripts for testing, building, etc., whatever you configure in your projects(ci-/cd-) pipeline (by using .gitlab-ci.yaml or the auto dev-ops pipeline).

What’s this about?

In this post I’ll cover how to set up a runner and connect it to gitlab.

apt-get install -y apt-transport-https ca-certificates software-properties-common

make sure to install latest ca-certificates and the packages needed to conveniently manage apt repositories.

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

execute the script.deb.sh, provided by gitlab. This basically identifies your OS Version (in my case: debian stretch), inserts the correct repository in you sources.list and imports the gpg.key. If it doesn’t work for some reason, just manually do apt-add-repository, wget gpg.key, apt-key add gpg.key.

apt-get -y install gitlab-runner

install the gitlab-runner package

gitlab-runner register

and register the runner.
This will ask for:

• your gitlab url
• a token

To get the token:

• log in to your gitlab admin account (standard: root)
• click the little tool icon (admin area) on the top left/middle.
• select runners on the left sidebar
• copy the token

That’s it!

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If you come here from “how to set up gitlab and work with it” and used self signed certificates from the how to.
Then you should import your CA-Certificate on the runner.

cp ca-root.crt /usr/local/share/ca-certificates/ca-root.crt
update-ca-certificates
systemctl daemon-reload
systemctl restart gitlab-runner

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Tips

If you plan to use your runner for building docker images (e.g. you want to build a pipeline) , you’ll need to configure some additional things:

vi /etc/gitlab-runner/config.toml

[[runners]]
  executor = "docker"
    environment = ["DOCKER_AUTH_CONFIG={\"auths\": { \"gitlab.my.domain\": { \"auth\": \"base64encodedcreds\" }}}"]

[runners.docker]
    tls-ca-file = "/etc/ssl/certs/ca-root.pem"
    tls_verify = false
    volumes = ["/var/run/docker.sock:/var/run/docker.sock","/cache"]
    dns = ["192.168.178.33"]

DOCKER_AUTH_CONFIG is available under ~/.docker/config.json after you have issued:

docker login -u usernme https://gitlab.your.domain:4567 

tls-ca-file might prove useful if you are working with self-signed certs.
tls_verify = false disables verification
dns tells docker to use a specific dns server, this helps if you encounter “cannot resolve..” errors.

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Troubleshooting Tips

• check your firewall
• check the config: (everything gitlab related and important is configured in /etc/gitlab-runner/config.toml)
• if docker still complains about dns, try to add dns servers to /etc/docker/daemon.json

"dns": ["192.168.178.33","192.168.178.1"]