Stock, the device runs a customised version of Linux. Linksys was required to release their
source code as per the terms of the
GNU General Public License. Due to the availability of source code, the NSLU2's use of well-documented commodity components and its relatively low price, there are several community projects centered around it, including hardware modifications, alternative firmware images, and alternative operating systems with varying degrees of reconfiguration.
Hardware modifications Unofficial hardware modifications include: • Doubling the clock frequency on underclocked units. As of summer 2006, the NSLU2 was sold without the "underclocking" • Addition of a
serial port • Addition of a
JTAG port • Enabling extra
USB ports • Addition of extra memory • NSLU2 units that have had their memory upgraded are commonly referred to as 'FatSlugs' • Devices have been successfully upgraded to 64 MB but not stable operation with 128 MB and 256 MB of RAM • The version with 256 MB RAM and 16 MB flash (twice the standard amount) has been nicknamed 'ObeseSlug' • Forced Power On • Adding an
HD44780 controlled dot matrix display
Alternative firmware Most of the alternative firmware projects are no longer functional. However
OpenWrt claims to still be working to maintain support for the device. There were two main replacement firmware images available for the device: the first is
Unslung which was based on the official Linksys firmware with some improvements and features added.
Optware packages were available to expand functionality. The other was
SlugOS/BE (formerly OpenSlug), which was based on the
OpenEmbedded framework. SlugOS/BE allowed users to re-flash the device with a minimal Linux system including an
SSH server to allow remote access. Once installed, the operating system had to be moved to an attached hard disk due to the lack of space available on the flash memory. Once this had been done, a wide range of additional packages were available to be installed from an Internet repository. It was also possible to run
Debian,
Gentoo,
FreeBSD,
NetBSD,
OpenBSD, and
Ubuntu on the device. The ability to run an unrestricted operating system on the device opened up a whole new range of uses. Some common uses were a
web server,
mail server,
DAAP server (iTunes),
XLink Kai,
UPnP AV MediaServers,
BitTorrent client,
FreeSWITCH,
asterisk PBX and
network router (with the attachment of a USB network interface/USB modem). German programmer Boris Pasternak developed the weather server program/server Meteohub as an inexpensive way to gather weather sensor data from personal weather stations ("PWS") and allow it to be posted on a number of online weather services including Weather Underground, Weatherbug, Citizens Weather Observation Program (CWOP), and many others. An NSLU2 with Unslung firmware could be interfaced with a
Topfield TF5800 personal video recorder (PVR) to allow an
electronic programme guide (EPG) to be automatically downloaded from the Internet and transferred to the PVR. ==Problems==