Tim Rightnour


Garbled's NetBSD Home Automation Scripting Tools

Gnhast is an event based home automation suite of tools. It relies on a central daemon, which handles all the coordination of work, and collectors which handle all the actual work. While the primary development environment is NetBSD, it should also work on any other version of UNIX or Linux.

The gnhast daemon itself runs on a server, and feeds data to/is fed data from collectors. It can respond to a change in the state of a device, by executing an external program. This program, is itself, a form of collector.

The collectors perform all the actual work in gnhast. A collector can perform a number of different functions:

1) Monitor a device, and tell gnhastd about the changes in that device. For example, monitoring a one-wire temperature probe, and continually updating gnhastd with the current temperature.

2) Make changes to a device. For example, the central daemon might tell the collector to turn off a light switch. The collector will issue the command to the light switch it controls, and update gnhastd with the status.

3) Simply collect data. A collector (such as rrdcoll) can simply receive data from gnhastd, and use it to update rrd files for making pretty graphs.

4) Make decisions. An external script (which is a form of collector) could be informed that the temperature of a one-wire device has changed. It can look at this new value, and decide that it's time to turn on a fan. It would tell gnhastd that the fan device should be turned on, and gnhastd will contact the appropriate collector.

The core system of gnhast is written in C. However, because the collectors are simply separate processes that communicate with gnhastd, they can be written in any language. Additionally, collectors that are not directly launched by gnhastd (scripts) communicate to gnhastd via a simple TCP API. Because of this, they could even reside on a different machine, or machines, than the master gnhastd.

Design Philosophy

Gnhast is based on UNIX, and attempts to make home automation more UNIX-like. If you like the way UNIX works, you will like gnhast. If you despise all the fiddly bits of UNIX, this is not for you.

There is no built-in pseudo-coding language for making decisions based on sensor data. Writing a good language parser is hard, and many people are better at it than I am. They wrote languages, alot of them even. Some people like perl, some people despise it. Gnhast works similarly to a UNIX kernel, it handles all the hardware, and provides a set API for working with it. If you want to write code that says "when it's light out, turn the outside lights off", then just do that. Write it in perl, python, whatever, and have gnhast just run your executable.

Do you want your garage door to open every night at 18:00? (yikes) Write a script to open the door, and put it in cron.

Finally, it's distributed. Each collector runs on a machine, and gnhastd runs on a machine. The machines do not have to be the same machine. Perhaps you wish to run the core gnhastd on a big server with a massive UPS, but you want to run the insteon collector on a Raspberry PI next to a power outlet in the laundry room. Maybe you have a dedicated machine running Cacti, and you want to run the rrd collector locally there. Gnhast lets you do all this.

Gnhast does not need to run as root. The only caveat, is that some of the collectors will need access to the serial devices connected to hardware, log files, and conf files. Use chown/chmod.

More Documentation

[gnhast protocol] - The Gnhast Protocol
[collectors] - The Collectors
[dependencies] - Dependencies
[todo list] - TODO List
[Getting Started] - Getting Started How-To
[Ideas on use] - Ideas for how to use gnhast, in a UNIXy way.
[Programming] - Notes on modifying gnhast or adding features.
[gnhastweb] - The web interface

The wiki uses Markdown syntax.

Project Members:


Wiki: Getting Started
Wiki: Ideas on use
Wiki: Programming
Wiki: collectors
Wiki: dependencies
Wiki: gnhast protocol
Wiki: gnhastweb
Wiki: todo list