Update gitlab_ci_demo.md

Author: MakisH

05_testing_and_ci/gitlab_ci_demo.md

@@ -25,38 +25,12 @@ Test code in [automation lecture repository](https://gitlab-sim.informatik.uni-s
     - Instances -> Launch instance
         - Ubuntu 24.04
         - Flavor: m1.small
-    - `sudo apt update && sudo apt -y upgrade`
-    - `sudo apt install -y docker.io`
 - VM is up and running, connect to it: `ssh ubuntu@<IP>`
+- Apply updates: `sudo apt update && sudo apt -y upgrade`
+- Install Docker: `sudo apt install -y docker.io`
 
 You can get the IP from the [Instances view](https://portal.bw-cloud.org/project/instances/). Note that there are two addresses here: an IPv4 (decimal) and an IPv6 (hexadecimal) address. New VMs on bwCloud only support IPv6 networks, so you need the second address.
 
-## Workarounds for IPv6
-
-New bwCloud VMs only support IPv6 by default. Asking for IPv4 for a specific VM might be possible via the [helpdesk](https://bw-cloud.org/q/t).
-
-A few workarounds are needed to make the GitLab runner work in this IPv6-only environment, especially since [`registry.gitlab.com` does not support IPv6](https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/18058) and the Docker support for IPv6 needs to be expliticly configured.
-
-First, we need to tell Docker to use the host network and DNS. We also need to replace the helper image with [the one from Docker Hub](https://hub.docker.com/r/gitlab/gitlab-runner-helper/tags?name=x86_64-v17.10.1). Edit the `[runners.docker]` section in `/srv/gitlab-runner/config/config.toml`:
-
-```toml
-  volumes = ["/etc/resolv.conf:/etc/resolv.conf:ro", "/srv/gitlab-runner/custom-hosts:/etc/hosts:ro", "/cache"]
-  helper_image = "gitlab/gitlab-runner-helper:x86_64-v17.10.1"
-  network_mode = "host"
-```
-
-While you could pass `--network host` to `docker run`, setting this system-wide makes it easier to also start the job containers with the same settings.
-
-Whenever changing this configuration file, we need to restart the runner (e.g., by restarting the respective container).
-
-We also need to hard-code the IPv6 address that corresponds to the GitLab instance domain. Add the following line in the `/srv/gitlab-runner/custom-hosts`:
-
-```
-2001:7c0:2015:216::19 gitlab-sim.informatik.uni-stuttgart.de
-```
-
-You can get this address by running `dig aaaa gitlab-sim.informatik.uni-stuttgart.de`.
-
 ## Setup GitLab Runner
 
 - Install GitLab Runner via Docker:
@@ -84,6 +58,7 @@ You can register a runner using the following command. Notice again the `--netwo
 
 ```bash
 sudo docker run --rm -it \
+         --network host \
          -v /srv/gitlab-runner/config:/etc/gitlab-runner \
          gitlab/gitlab-runner register \
          --url https://gitlab-sim.informatik.uni-stuttgart.de/
@@ -92,14 +67,42 @@ sudo docker run --rm -it \
 - Enter the following details:
     - URL: (press Enter to confirm)
     - Token: see above
-    - Description: `SSE Automation Demo Runner`
+    - Name/Description: `SSE Automation Demo Runner`
     - No tags, no maintenance note
     - Executor: `docker`
     - Default Docker image: `alpine:latest` (used for pipelines that do not specify any Docker image themselves, can be overwritten in configuration of pipeline)
 - `sudo vi /srv/gitlab-runner/config/config.toml`
 - Verify that there is now a runner in the repo settings
 - Verify that pipeline now ran
 
+The `--network host` is needed in this IPv6-only VM (see section below).
+
 - More information:
     - [Executors and their abilities](https://docs.gitlab.com/runner/executors/)
     - [Registering runners](https://docs.gitlab.com/runner/register/index.html#docker).
+
+## Workarounds for IPv6
+
+New bwCloud VMs only support IPv6 by default. Asking for IPv4 for a specific VM might be possible via the [helpdesk](https://bw-cloud.org/q/t).
+
+A few workarounds are needed to make the GitLab runner work in this IPv6-only environment, especially since [`registry.gitlab.com` does not support IPv6](https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/18058) and the Docker support for IPv6 needs to be expliticly configured.
+
+First, we need to tell Docker to use the host network and DNS. We also need to replace the helper image with [the one from Docker Hub](https://hub.docker.com/r/gitlab/gitlab-runner-helper/tags?name=x86_64-v17.10.1) (depends on the GitLab version. You can start without this setting, and see which image GitLab is trying to pull). Edit the `[runners.docker]` section in `/srv/gitlab-runner/config/config.toml`:
+
+```toml
+  volumes = ["/etc/resolv.conf:/etc/resolv.conf:ro", "/srv/gitlab-runner/custom-hosts:/etc/hosts:ro", "/cache"]
+  helper_image = "gitlab/gitlab-runner-helper:x86_64-v17.10.1"
+  network_mode = "host"
+```
+
+While we already pass `--network host` to `docker run`, setting this system-wide makes it easier to also start the job containers with the same settings.
+
+Whenever changing this configuration file, we need to restart the runner (e.g., by restarting the respective container).
+
+We also need to hard-code the IPv6 address that corresponds to the GitLab instance domain. Add the following line in the `/srv/gitlab-runner/custom-hosts` (create the file):
+
+```
+2001:7c0:2015:216::19 gitlab-sim.informatik.uni-stuttgart.de
+```
+
+You can get this address by running `dig aaaa gitlab-sim.informatik.uni-stuttgart.de`.