Category: GitLab

How to Run and Update Docker Images and Containers

The following text shows the default workflow to run and update a Docker image based on the example of GitLab. But this should also work for other containers.

Docker Installation

First make sure that your local machine has Docker installed. I use Debian and for this, a detailed description is available in Dockers documentation. There are also instructions for CentOS, Ubuntu, Fedora and others.

You can check the installed Docker version:

docker version
Client: Docker Engine - Community
 Version:           20.10.11
 API version:       1.41

Run a Docker Container

Let’s start with an environment variable that defines the path where all the Gitlab data is stored. This is outside of the Docker container which allows an easy update without loosing data. To define the variable $GITLAB_HOME, you can use:

export GITLAB_HOME="/srv/gitlab"

To run a Docker container, simply use the run command with your parameters. For GitLab, this might look like:

docker run --detach
  --hostname <>
  --publish 443:443 --publish 80:80 --publish 2222:22
  --name gitlab
  --restart always  
  --volume $GITLAB_HOME/config:/etc/gitlab 
  --volume $GITLAB_HOME/logs:/var/log/gitlab
  --volume $GITLAB_HOME/data:/var/opt/gitlab

You should use your own settings and replace <> with your setup.

For the sake of completeness, you might also need a runner for GitLab. Let’s run this container as well:

docker run --detach 
  --name gitlab_runner
  --restart always 
  --network host 
  -v /run/docker.sock:/var/run/docker.sock 

And this one needs to be registered in your GitLab instance:

docker exec -it gitlab_runner gitlab-runner register 
  --url https://<>/
  --registration-token <registration_token>

More details about the configuration of the GitLab runner is descriped in this post.

Update a Docker Container to the Latest Version

Let’s check, which container are running by using:

docker ps

The output shows all your containers and their ids:

CONTAINER ID   IMAGE                         COMMAND                  CREATED       STATUS                 NAMES
02fe426970f1   gitlab/gitlab-ce:latest       "/assets/wrapper"        4 hours ago   Up 4 hours (healthy)   gitlab
5742e07f809b   gitlab/gitlab-runner:latest   "/usr/bin/dumb-init …"   4 days ago    Up 5 hours             gitlab_runner

We have to stop the container and remove the image. When you used a run command (for GitLab) as shown above, this should not affect the data as this is stored outside of the container.

docker stop 02fe426970f1
docker rm 02fe426970f1

To remove the associated image, you can use the docker rmi. For this, we need to find the id of this image by listing all images:

docker images
REPOSITORY         TAG      IMAGE ID       CREATED        SIZE
gitlab/gitlab-ce   latest   46cd6954564a   17 hours ago   2.36GB
mysql              5.7      c20987f18b13   2 weeks ago    448MB
cirrusci/flutter   2.8.1    98a87781f179   2 weeks ago    3.49GB

Now we can remove the image (in my case the gitlab-ce image):

docker rmi 46cd6954564a

The update of the image can be done by using pull. This will download the images (in this case the latest version) and stores it on your system:

docker pull gitlab/gitlab-ce:latest

After this, you can use the same run command as before to run a container with the updated image:

docker run --detach
  --hostname <>
  --publish 443:443 --publish 80:80 --publish 2222:22
  --name gitlab
  --restart always  
  --volume $GITLAB_HOME/config:/etc/gitlab 
  --volume $GITLAB_HOME/logs:/var/log/gitlab
  --volume $GITLAB_HOME/data:/var/opt/gitlab

A final check, shows the container is up and running:

docker ps
CONTAINER ID   IMAGE                         COMMAND                  CREATED        STATUS                 NAMES
f3dab1163c07   gitlab/gitlab-ce:latest       "/assets/wrapper"        2 minutes ago  Up 4 hours (healthy)   gitlab
5742e07f809b   gitlab/gitlab-runner:latest   "/usr/bin/dumb-init …"   4 days ago     Up 5 hours             gitlab_runner

Instead of automatically using the latest version of each image (e.g. gitlab/gitlab-ce:latest) you can also specify a version number like gitlab/gitlab-ce:14.5.2. This is helpful when you need to update a system in steps. Or if you need to follow a specific upgrade path, which is the case for GitLab.

Photo by Ian Taylor on Unsplash.

GitLab – ERROR: Registering runner… failed, certificate signed by unknown authority

If your self-hosted GitLab server is using a self-signed certificate for https, it might be possible that you get an error during the registration of a GitLab Runner:

ERROR: Registering runner... failed        runner=HbU25D-y status=couldn't execute POST against Post x509: certificate signed by unknown authority
PANIC: Failed to register the runner. You may be having network problems.

To solve the problem, you have to provide the full chain certificate *.pem used by your GitLab Server:

gitlab-runner register --tls-ca-file /path/to/fullchain.pem

In my case, the valid certificate could be found on the GitLab server in /etc/gitlab/trusted-certs/fullchain.pem. This one was copied to the GitLab Runner server and used in the command above.

As I did not set up the server on my own, I do not know if this is the default path and filename of a certificate signed by Let’s Encrypt. But in my case, this one worked to register the runner.

Run GitLab console on Synology NAS

As the Synology DSM uses Docker to run GitLab, we can use Docker as well to install GitLab Runner. For this, connect to the Synology using SSH:

ssh <admin-user>@<synology> -p <port>

To connect to the GitLab container, you can use the following command to open:

docker exec -it synology_gitlab /bin/bash

You might adjust the name of the GitLab docker depending on your system.

To open the console, run:

gitlab-rails console

When GItLab is installed using the DSM package manager, just use the following commands:

cd /home/git/gitlab/bin
./rails console production

Commands for the console

Below are some examples how to use the GitLab console.

Check the mail delivery method


Output might be: => :smtp

Check the smtp settings


Output might be: => {:address=>"", :port=>25, …

Testing the SMTP configuration (see documentation)

Notify.test_email('', 'Subject', 'Mail Body').deliver_now

GitLab on Synology: set ‘external_url’

There are two (or even more) solutions to install GitLab on a Synology:

  • Using Docker and the container gitlab/gitlab-ce
  • Using the DSM package manager

Depending on the type of installation, different settings are required to update the external url.

Using Docker container

The external url of GitLab can e defined in /etc/gitlab/gitlab.rb. The parameter takes an url and can also handle a port:

external_url ''

Important: when a port is specified in external_url, this will override the https/https port where nginx is listening. To use a different port for nginx, this requires an additional setting:

nginx['listen_port'] = 80

After changing this setting, it’s necessary to run:

gitlab-ctl reconfigure

The settings above are necessary, if port routing is set like the following:

Using DSM package manager installation

This installation of GitLab on Synology uses localhost as a default value for external url. This may lead to some problems when accessing GitLab over another IP or host name. In my case, this lead to missing icons and a non functional WebIDE. An inspection of the html page shows, that some resources are requested over http://localhost/... which leads to 404 errors for those resources.

Since the GitLab container on Synology is not based on the omnibus package, you can not use directly external_url in /etc/gitlab/gitlab.rb. If you want to change the url you can do it by changing the docker environment parameter GITLAB_HOST.

GitLab on Synology: Environment settings