Add rebuilderd documentation

README.md

@@ -238,8 +238,10 @@ So to set up this server from scratch, run:
 
 ### reproducible.archlinux.org
 
+[Rebuilderd docs](./docs/rebuilderd.md)
+
 #### Services
-  - Runs a master [rebuilderd](docs/rebuilderd.md) instance two workers:
+  - Runs a master [rebuilderd](https://reproducible.archlinux.org) instance two workers:
     - repro1.pkgbuild.com (packet.net Arch Linux box)
 
 ### runner2.archlinux.org

docs/rebuilderd.md

+## Rebuilderd
+
+We host a [Rebuilderd](https://github.com/kpcyrd/rebuilderd) instance on reproducible.archlinux.org which rebuilds Arch packages from repositories defined in `rebuilderd-sync.conf`. Workers automatically connect to the configured rebuilderd instance and query it for work and publish results to the rebuilderd instance.
+
+Results are shown on [our website](https://reproducible.archlinux.org) which is a [rebuilderd-website](https://gitlab.archlinux.org/archlinux/rebuilderd-website) instance.
+
+## Configuration
+
+Setting up rebuilderd-workers requires adding the `rebuilderd_worker` role to the playbook and adding `rebuilderd_workers` a list with rebuilderd-worker names for example:
+
+```
+rebuilderd_workers:
+ - repro11
+ - repro12
+```
+
+## Monitoring
+
+The rebuilderd workers and queue are monitored by Prometheus.
+
+## Common commands
+
+Checking rebuilderd-workers status on reproducible.archlinux.org:
+
+```
+rebuildctl status
+```
+
+Checking rebuilderd queue length:
+
+```
+rebuildctl queue ls
+```