add docker file to build the image

Dockerfile

+FROM alpine:latest
+
+ENV SSL_CERT_FILE /etc/ssl/cert.pem
+
+RUN echo '@edge/testing http://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories \
+    && apk upgrade -U --no-cache \
+    && apk add -U --no-cache \
+        gitlab-runner@edge/testing \
+    && adduser -D -S -h /home/gitlab-runner gitlab-runner
+
+COPY register-runner /usr/local/bin
+
+VOLUME ["/etc/gitlab-runner", "/home/gitlab-runner"]
+ENTRYPOINT ["/usr/bin/gitlab-runner"]
+CMD ["run", "--user=gitlab-runner", "--working-directory=/home/gitlab-runner"]
+

README.md

@@ -2,3 +2,37 @@
 
 This will create a docker image for running a gitlab runner on Alpine Linux on
 all the architectures that Alpine Linux supports.
+
+## Starting the runner
+
+To run the container, 1 required and 2 optional volumes need to be attached:
+
+* docker socket (/var/run/docker.sock)
+* conf dir (/etc/alpine-runner)
+* home dir (/home/gitlab-runner)
+
+For example:
+
+```sh
+docker run -d \
+    -v /srv/gitlab-runner/conf:/etc/gitlab-runner \
+    -v /srv/gitlab-runner/home:/home/gitlab-runner \
+    -v /var/run/docker.sock:/var/run/docker.sock \
+    gitlab-runner
+```
+
+You can execute `./run` to run this command
+
+## Register the runner
+
+There is a `./register-runner` command available in the container to register it.
+
+To execute it, use the following command:
+
+```sh
+docker exec -e ARCH=<arch> -e GITLAB_REGISTER_TOKEN=<token> <container> register-runner
+```
+
+* `ARCH` is added as a tag on the runner
+* `GITLAB_REGISTER_TOKEN` is a token you can find under `Settings > CI / CD > Runners`
+  of a specific project or under `Admin > Overview > Runners`.

docker-compose.yml

+version: 3
+services:
+  gitlab-runner:
+    build: .
+    volumes:
+      - /srv/gitlab-runner/conf:/etc/gitlab-runner
+      - /srv/gitlab-runner/home:/home/gitlab-runner
+      - /var/run/docker.sock:/var/run/docker.sock

register-runner

+#!/bin/sh
+
+gitlab-runner register \
+  --non-interactive \
+  --url "https://gitlab.alpinelinux.org/" \
+  --registration-token "$GITLAB_REGISTER_TOKEN" \
+  --executor "docker" \
+  --docker-image alpine:latest \
+  --description "docker-runner ($ARCH)" \
+  --tag-list "docker-alpine,$ARCH" \
+  --run-untagged="true" \
+  --locked="false" \
+  --access-level="not_protected"

run

+#!/bin/sh
+
+name=${1-gitlab-runner}
+
+docker run -d \
+    -v /srv/gitlab-runner/conf:/etc/gitlab-runner \
+    -v /srv/gitlab-runner/home:/home/gitlab-runner \
+    -v /var/run/docker.sock:/var/run/docker.sock \
+    --name $name \
+    gitlab-runner