GITBOOK-32: No subject

Author: Filip

docs/controller/os.md

@@ -1,2 +1,43 @@
 # OS
 
+## Description
+
+Robopipe OS is a custom pre-configured OS image based on [Debian](https://www.debian.org/). It comes with all the packages and tools you need to build a AI/CV application pre-installed. You can find all releases along with the configuration scripts in [this repository](https://github.com/Robopipe/OS).
+
+## Default configuration
+
+### Users
+
+The default user you should use when working on the controller directly is `admin`. The password is `robopipe.io`.
+
+### Hostname & mDNS
+
+A hostname is assigned to the controller on startup. The assigned hostname is in the format `robopipe-<id>`, where _id_ is determined dynamically on each startup. When the controller is started it will scan the local network, and assign itself the lowest possible _id_ which is not already taken. This means that the first controller you start will have _id_ 1, the next will have _id_ 2 and so on. At the same time, it will also broadcast an [mDNS](https://en.wikipedia.org/wiki/Multicast_DNS) record based on its hostname (`robopipe-<id>.local`). This means that the controller can be addresses not only by its IP address, but also by its hostname in the local network. This behaviour is enabled via `robopipehostname` service, if you wish to disable it, you can do so using:
+
+```bash
+sudo systemctl disable robopipehostname # this will take effect on the next startup
+```
+
+### SSH
+
+SSH server is running on the controller by default on port 22.
+
+### Robopipe API
+
+Robopipe API is configured to start automatically at startup. If you wish to disable this, you can do so using:
+
+```bash
+sudo systemctl disable robopipeapi
+```
+
+## Service Mode
+
+Sevice mode is used for backing up the operating system, uploading new OS images or restoring access to the unit. This mode does not publish an mDNS record.
+
+### Entering the Service Mode
+
+* Turn off the controller
+* Press and hold the _SERVICE_ button on your controller (usually located next to USB labels)
+* Turn on the controller while still hodling the _SERVICE_ button
+* Release the _SERVICE_ button when all the LEDs start blinking periodically
+