Kaliko Systems Limited

Make a Low-Power Media Server

Downloader Overview

This project is to build a bit-torrent download device, that is:
Silent - no fans and no hard disks; so fine in a bedroom.
Low Power - can be left on 24x7 at a few dollars a year electricity cost.
Low Cost - about $140 for new components (Amazon.com prices).
Small Sized - approx 13cm x 16cm x 5cm (5in x 6in x 2in).
Simple to Build - takes about 3 hours and no electronic skills required.
Easy to Use - all operational control is from your Windows or other home PCs.

Requirement and Approach

The requirement is to have a low-power device providing bit-torrent downloading, that allows the PCs in your house to control and retrieve the downloads, without needing any PC to be powered on for the duration of the downloads.

The approach uses standard components in well-understood ways. The components are:
Transmission - a standard free bit-torrent download application, but it is unusual in having an optional web server front-end.
Linksys NSLU2 - designed as a low power, simple Network Attached Storage (NAS) device. It performs this role well and simply looks like a networked Windows PC to other computers. However, it is quite easy to convert a NSLU2 to a general-purpose small Linux computer, by replacing the Linksys Linux operating system. Note, this process requires flashing your NSLU2 firmware, so is not fool-proof and invalidates your warranty.
Unslung - a replacement Linux operating system for the NSLU2. This is used, as it keeps the Linksys web management for simple remote system control, and supports the Transmission application well.
8 Gbyte or Larger USB2 Pen Drive - these can usually hold quite a few downloads and also provides a silent boot and running drive for unslung on the NSLU2.

There are no techniques here that are not explained elsewhere on web sites (mostly in http://www.nslu2-linux.org and http://www.transmissionbt.com/). However, this document filters the huge range of techniques covered on these web sites, to only those required for building a simple and effective bit-torrent downloader. The result is an easy to use device that consumes about 5 watts.

Getting the Components

Linksys NSLU2 - many on-line retailers stock the NSLU2. However, if you buy a used NSLU2 then restoring to factory defaults, as described in the Linksys CD manual chapter 2, is essential. Also be aware that in old NSLU2s the CPU ran at half the current model's speed, i.e. 133MHz instead of 266MHz. This can be checked and modified anytime after you have finished the "Instal Unslung on Pen Drive" page, see "Optionally Tailoring System" page for details.

8 GB or Larger USB2 Pen Drive - the larger the pen drive the better. After purchase, use the Windows Disk Manager (under Control Panel/Administrative Tools/Computer Management) to check if the pen drive has multiple partitions. If it has, you must delete all the partitions and make a new primary partition on the pen drive, then format it to FAT32 (not quick format). First, try using Windows Disk Manager to delete the partitions. To delete a U3 tools partition, a special tool must be downloaded; see the U3 support page at http://www.u3.com. Tools for other difficult to delete partitions should be available on the pen drive manufacturer's web site.
An alternative to a conventional pen drive is to use a smart card in a USB holder.

Unslung Operating System - a free download (ref. 1 - Downloads page).

Transmission Application - a free download, but needs to be downloaded from within unslung (as described later).

Tools

PC - any modern version of Windows (can also use Linux or Mac). This project is described based on Windows XP. For Mac users and other versions of Windows, I will add any helpful comments emailed to me.
Web Browser - Internet Explorer, Firefox or similar on your PC.
Linux Compatible Text Editor - for Windows use WordPad (not NotePad as you will see if you try it). For XP, WordPad is not in the Programs/Accessories list, but is at C:\Program Files\Windows NT\Accessories\wordpad.exe
Spare Ethernet Port on your Router or Hub - this should be checked to make sure it is working.

Overview of Work

  1. Get the NSLU2 working as standard, on your home network.
  2. Replace the Linksys operating system with "unslung" running on a pen drive (to change your NSLU2 into a small silent Linux Computer).
  3. Install and configure the Transmission application to provide a web server based bit-torrent download capability, controllable from your home PCs.
  4. Test downloading works correctly.
  5. Optionally tailor the system to your needs.

So lets start with getting the NSLU2 working as standard.
Copyright (c)2009 Kaliko Systems Limited