ARM Linux
ARM Linux is a port of Linux to ARM-processor-based machines. The ARM port runs on several different machine and processor architectures, including complete computers, network computers and evaluation boards. There are also projects for porting Linux to palmtops and PDAs (like the Geofox).

BlueCat Linux
BlueCat Linux, due to be released in January 2000, is a port of Red Hat Linux optimized for embedded applications, It's developed by Lynx Real-Time Systems, the firm that does the LynxOS operating system for embedded applications.

ELKS
ELKS--the Embeddable Linux Kernel Subset--began life as a project for creating a distribution of Linux for 8086 and 80286 PCs, but was expanded to support Linux on palmtop computers, single-board microcomputers, and embedded controller systems. The ELKS kernel image needs about 200K, and a full running system should require 400K-512K. The ELKS source releases include ready-built kernel and root disk images.

EMJ-Linux
EMJ Embedded Systems has developed a small Linux distribution (based on Slackware 4.0) that runs on JUMPtec’s DIMM-PC/486, one of the world’s smallest PCs--a full-featured 486 PC in the size of a 144-pin memory DIMM. It measures 40x68 mm (1.57 x 2.68 inches) and is designed for high-performance applications, such as security apparatuses, medical instruments, factory automation and global positioning systems. It ships with 16 MB of DRAM, 16 MB of IDE compatible flash and supports two serial ports and a parallel port, as well as floppy and hard drive interfaces, a real time clock and watchdog timer and an I2C-bus. The EMJ-linux distribution consists of a 1.4MB bootdisk containing everything needed to do a network install of EMJ-linux. Once loaded, the DIMM-PC with Linux supports Ethernet, TCP/IP, telnet, FTP, Apache 1.3.9, as well as two serial ports, parallel, floppy, IDE and VGA.

et-linux
et-linux is a complete Linux system designed to run on small industrial computers. The 1.0 and 1.1 systems are based on libc-5 and Linux kernel 2.0, while Et-Linux 1.2 is based on glibc 2.1.2. Although the et-linux project includes the device drivers for EuroTech peripherals, this release is pretty general (the drivers are available separately as etdrive-0.05.tar.gz from the same FTP site as the rest of et-linux). It includes a cgi-capable Web server, a simplified telnet server running on port 2300 and an e-mail server.

Embedix
Lineo is developing a unique distribution of Linux specifically targeted at embedded devices. This development includes re-engineering existing Linux packages to take advantage of reduced memory, storage and processor speeds common in embedded devices, as well as developing new Linux packages for the embedded environment, including non-X-based graphical APIs and extensions for placing Linux in FLASH RAM. The effort is centered around the Embedix platform. Embedix is an embedded Linux kernel, libraries, API sets, applications, source components and meta-information required for customization of the OS and its packages. The Embedix SDK is an embedded software development kit that includes a complete distribution of OpenLinux, development tools (compilers, debuggers, profilers), a graphical IDE, ISV applications and Target Wizard, Lineo's automated component selection and configuration tool.

Linux Router
This networking-centric micro-distribution of Linux, developed by the Linux Router Project, is small enough to fit on a single 1.44MB floppy disk. It's designed for building and maintaining routers, access servers, thin servers, thin clients, network appliances and typically embedded systems that are next to trivial in size.

RTLinux
Technically, RTLinux (RealTime Linux) isn't really a Linux distribution, but rather an extension to Linux that handles time-critical tasks. In RTLinux, a small hard-realtime kernel and standard Linux share one or more processors, so that the system can be used for applications like data acquisition, control, and robotics while still serving as a standard Linux workstation. There are two versions of RTLinux: the current version, V2, offers a POSIX style application programming interface (API), supports SMP, and runs on Linux 2.2; an earlier version, V1, runs on Linux 2.0 and provides a simple RT API and does not support SMP.
Added on Nov. 26.

uC-linux
uC-linux is a Linux distribution designed for the Motorola ColdFire processor family. First released in 1994, ColdFire embodies a variable-length RISC architecture that is designed to meet the requirements of the embedded consumer market. It's a derivative of the 68k architecture, removing instructions and addressing modes that are slow or not often used. The code is based on Linux kernel version 2.0.38, with the uC-linux patches applied. The libm and parts of the libc libraries and some of the user applications also come from the uC-linux work.

VMELinux
Currently supporting the Tundra Universe PCI-VME, this project has the goal of supporting Linux on the VMEbus.

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