From 195776718c83be8bb6ab5fa51483f8350c94321e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20Jochum?= <rene@jochums.at>
Date: Thu, 19 Apr 2018 15:25:40 +0200
Subject: [PATCH] Add post gitlab runner docker with systemd
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Signed-off-by: René Jochum <rene@jochums.at>
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+---
+date: 2018-04-17T22:54:00+02:00
+title: gitlab-runner docker with debian systemd
+author: pcdummy
+tags:
+  - HOWTO
+  - Debian
+  - Gitlab
+  - Docker
+---
+
+An howto on systemd with a Debian stretch/buster docker container and Gitlab.
+<!--more-->
+
+Find all code on Github [stretch](https://github.com/pcdummy/proxmox-dockerfiles/tree/master/stretch-systemd) and [buster](https://github.com/pcdummy/proxmox-dockerfiles/tree/master/buster-systemd).
+
+### Debian Stretch
+
+This didn't work at all with systemd from Debian stretch, but as i knew from my LXD experience systemd in stretch is buggy with containers,
+so i tried systemd from [stretch-backports](https://github.com/pcdummy/proxmox-dockerfiles/blob/master/stretch-systemd/Dockerfile#L18) which worked well.
+
+Now to have systemd finaly working in a stretch container you need to mount a tmpfs into /run and /run/lock else systemd tries to mount those - fails with permission denied and freezes.
+
+Also you need to bind-mount cgroups into the stretch container (doing that as "volume").
+
+This is the full line to run a Debian 9 container with systemd from backports:
+
+```
+docker run -d -it --mount type=tmpfs,destination=/run --mount type=tmpfs,destination=/run/lock -v /sys/fs/cgroup:/sys/fs/cgroup:ro <image>
+```
+
+### Debian Buster
+
+It's same as with stretch but no backports.
+
+
+### Gitlab-runner for both
+
+Ok, so we found out that we need:
+
+- a tmpfs /run
+- a tmpfs /run/lock
+- cgroup bind-mount
+
+gitlab-runner does volumes which means the bind-mount is easy to solve, but what about the tmpfs mounts?
+
+After a while a found a feature they call [Mounting a directory in RAM](https://docs.gitlab.com/runner/executors/docker.html#mounting-a-directory-in-ram), which is nothing else than a mount of a tmpfs :)
+
+This means we need to add the following to **/etc/gitlab-runner/config.toml**:
+
+```toml
+[runners.docker]
+    volumes = ["/sys/fs/cgroup:/sys/fs/cgroup:ro", "/cache"]
+[runners.docker.services_tmpfs]
+    "/run" = "rw"
+    "/run/lock" = "rw"
+```
+
+Easy, isn't it?
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