NSLU2
Encyclopedia
The NSLU2 is a Network-attached storage
(NAS) device made by Linksys
introduced in 2004 and discontinued in 2008. It makes USB
Flash memory
and hard disk
s accessible over a network using the SMB
protocol (also known as Windows file sharing or CIFS). It was superseded mainly by the NAS200
(enclosure type storage link) and in another sense by the WRT600N and WRT300N/350N which both combine a wifi router with a storage link.
The device runs a modified version of Linux
and by default, formats hard disks with the ext3
filesystem, but a firmware upgrade from Linksys adds the ability to use NTFS
and FAT32
formatted drives with the device for better Windows
compatibility. The device has a web interface from which the various advanced features can be configured, including user and group permissions and networking options.
-compatible Intel
XScale
IXP420 CPU. In models manufactured prior to around April 2006, Linksys had underclocked
the processor to 133 MHz, though a simple hardware modification to remove this restriction is possible. Later models (circa. May 2006) are clocked at the rated speed of 266 MHz. The device includes 32 MB of SDRAM
, and 8 MB of Flash memory
. It also has a 100 megabit Ethernet network connection. The NSLU2 is fanless, making it completely silent.
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.
There are two main replacement firmware images available for the device: the first is Unslung
which is based on the official Linksys firmware with some improvements and features added. Optware
packages are available to expand functionality. The other is SlugOS
/BE (formerly OpenSlug), which is based on the OpenEmbedded
framework. SlugOS/BE allows users to re-flash the device with a minimal Linux system including an SSH
server to allow remote access. Once installed, the operating system must be moved to an attached hard disk due to the lack of space available on the Flash memory. Once this has been done, a wide range of additional packages are available to be installed from an Internet repository.
It is also possible to run OpenWrt
, Debian
, Gentoo
, FreeBSD
, NetBSD
, and Ubuntu
on the device.
The ability to run an unrestricted operating system on the device opens up a whole new range of uses. Some common uses are 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).
Network-attached storage
Network-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
(NAS) device made by Linksys
Linksys
Linksys by Cisco, commonly known as Linksys, is a brand of home and small office networking products now produced by Cisco Systems, though once a separate company founded in 1995 before being acquired by Cisco in 2003...
introduced in 2004 and discontinued in 2008. It makes USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
Flash memory
Flash memory
Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
and hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
s accessible over a network using the SMB
Server Message Block
In computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...
protocol (also known as Windows file sharing or CIFS). It was superseded mainly by the NAS200
NAS200
The NAS200 is a network-attached storage appliance intended for the consumer market. It was originally marketed by the Linksys division of Cisco Systems in 2007....
(enclosure type storage link) and in another sense by the WRT600N and WRT300N/350N which both combine a wifi router with a storage link.
The device runs a modified version of Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and by default, formats hard disks with the ext3
Ext3
The ext3 or third extended filesystem is a journaled file system that is commonly used by the Linux kernel. It is the default file system for many popular Linux distributions, including Debian...
filesystem, but a firmware upgrade from Linksys adds the ability to use NTFS
NTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....
and FAT32
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
formatted drives with the device for better Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
compatibility. The device has a web interface from which the various advanced features can be configured, including user and group permissions and networking options.
Hardware
The device has two USB 2.0 ports for connecting hard disks and uses an ARMARM architecture
ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
-compatible Intel
Intel Corporation
Intel Corporation is an American multinational semiconductor chip maker corporation headquartered in Santa Clara, California, United States and the world's largest semiconductor chip maker, based on revenue. It is the inventor of the x86 series of microprocessors, the processors found in most...
XScale
XScale
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
IXP420 CPU. In models manufactured prior to around April 2006, Linksys had underclocked
Underclocking
Underclocking, also known as downclocking, is the practice of modifying a synchronous circuit's timing settings to run at a lower clock rate than it was specified to operate at. It may be said to be the computer equivalent of driving a car below the speed limit...
the processor to 133 MHz, though a simple hardware modification to remove this restriction is possible. Later models (circa. May 2006) are clocked at the rated speed of 266 MHz. The device includes 32 MB of SDRAM
SDRAM
Synchronous dynamic random access memory is dynamic random access memory that is synchronized with the system bus. Classic DRAM has an asynchronous interface, which means that it responds as quickly as possible to changes in control inputs...
, and 8 MB of Flash memory
Flash memory
Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
. It also has a 100 megabit Ethernet network connection. The NSLU2 is fanless, making it completely silent.
User community
Stock, the device runs a customised version of Linux. Linksys was required to release their source codeSource code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
as per the terms of the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
. 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 portSerial portIn computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
- Addition of a JTAGJTAGJoint Test Action Group is the common name for what was later standardized as the IEEE 1149.1 Standard Test Access Port and Boundary-Scan Architecture. It was initially devised for testing printed circuit boards using boundary scan and is still widely used for this application.Today JTAG is also...
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 16MB flash (twice the standard amount) has been nicknamed 'ObeseSlug'
- Forced Power On
- Adding an HD44780 controlled dot matrix display
Alternative firmware
Unslung
Unslung is an open source firmware for the Linksys NSLU2. It is based on the stock Linksys firmware. Due to the device running Linux, and therefore licensed under, and subject to the terms of the GNU General Public License, Linksys released the source code....
which is based on the official Linksys firmware with some improvements and features added. Optware
Optware
Originally created for the Linksys NSLU2 Unslung firmware, Optware is an advanced package manager used for distribution of additional software packages on various operating systems.-What is Optware?:...
packages are available to expand functionality. The other is SlugOS
SlugOS
SlugOS is common source base for a group of firmware distributions for the Linksys NSLU2.-SlugOS:SlugOS comprises:*SlugOS/BE - Big Endian*SlugOS/LE - Little Endian*UcSlugC --SlugOS/BE:...
/BE (formerly OpenSlug), which is based on the OpenEmbedded
OpenEmbedded
OpenEmbedded is a software framework to create Linux distributions aimed for, but not restricted to, embedded devices. The build system is based on BitBake recipes, which behave similar to Gentoo's ebuilds....
framework. SlugOS/BE allows users to re-flash the device with a minimal Linux system including an SSH
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
server to allow remote access. Once installed, the operating system must be moved to an attached hard disk due to the lack of space available on the Flash memory. Once this has been done, a wide range of additional packages are available to be installed from an Internet repository.
It is also possible to run OpenWrt
OpenWrt
OpenWrt is a Linux distribution primarily targeted at routing on embedded devices. It comprises a set of about 2000 software packages, installed and uninstalled via the opkg package management system. OpenWrt can be configured using the command-line interface of BusyBox ash, or the web interface...
, Debian
Debian
Debian is a computer operating system composed of software packages released as free and open source software primarily under the GNU General Public License along with other free software licenses. Debian GNU/Linux, which includes the GNU OS tools and Linux kernel, is a popular and influential...
, Gentoo
Gentoo Linux
Gentoo Linux is a computer operating system built on top of the Linux kernel and based on the Portage package management system. It is distributed as free and open source software. Unlike a conventional software distribution, the user compiles the source code locally according to their chosen...
, FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, NetBSD
NetBSD
NetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...
, and Ubuntu
Ubuntu (operating system)
Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...
on the device.
The ability to run an unrestricted operating system on the device opens up a whole new range of uses. Some common uses are a web server
Web server
Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....
, mail server
Mail transfer agent
Within Internet message handling services , a message transfer agent or mail transfer agent or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture...
, DAAP server (iTunes)
Digital Audio Access Protocol
The Digital Audio Access Protocol is the proprietary protocol introduced by Apple in its iTunes software to share media across a local network....
, XLink Kai
XLink Kai
XLink Kai is a method developed by Team-XLink for online play of certain compatible console games.It enables players on the Xbox 360, Xbox, Playstation 3, PlayStation 2, PlayStation Portable and Nintendo GameCube to play games across the Internet using a network configuration that simulates a...
, UPnP AV MediaServers, BitTorrent client, FreeSWITCH
Freeswitch
FreeSWITCH is a free and open source communications software for the creation of voice and messaging products. It is licensed under the Mozilla Public License , a free software license...
, asterisk PBX
Asterisk PBX
Asterisk is a software implementation of a telephone private branch exchange ; it was created in 1999 by Mark Spencer of Digium. Like any PBX, it allows attached telephones to make calls to one another, and to connect to other telephone services including the public switched telephone network and...
and network router (with the attachment of a USB network interface/USB modem).
Problems
- Along with most NASs, the device isn't out-of-the-box compatible with Windows Vista, as it runs an older version of SambaSamba (software)Samba is a free software re-implementation, originally developed by Andrew Tridgell, of the SMB/CIFS networking protocol. As of version 3, Samba provides file and print services for various Microsoft Windows clients and can integrate with a Windows Server domain, either as a Primary Domain...
that uses an authentication mechanism that is disabled by default in Vista.
- Later builds of the system use more recent firmware than versions downloadable from the official websites. In the past, the UK website had more outdated firmware than the US website.
- The device with stock firmware had some compatibility issues with certain hard drives.
- The device will not power on automatically when it gets power from an external supply. This might be a problem in an environment where power failures are frequent. Automatic-power-on behavior can't be achieved on the device without hardware modifications.
Awards
The NSLU2 won the "Most Innovative in Networking" Reader Award in the Tom's Hardware 2004 Awards.Similar Devices
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Home Base F5L049 (with GPL firmware)