View source for ΜClinux

{{more citations needed|date=December 2011}}
{{lowercase title|μClinux}}
{{Infobox OS
| name = μClinux
| logo = 
| screenshot = Ipod linux booting kernel.jpg
| caption = An [[iPod classic|iPod]] booting [[iPodLinux]], based on μClinux
| website = {{webarchive |url=https://web.archive.org/web/20181113230737/http://www.uclinux.org/ |title=uclinux.org}}
| family = [[Embedded Linux]]
| source_model = [[Open-source software|Open source]]
| latest_release_version = 
| latest_release_date = {{Start date and age|2014|5|4}}
| kernel_type = [[Linux kernel]]-fork
| userland = uClinux-dist, [[uClibc]], [[BusyBox]]
| license = 
| working_state = Current
| supported_platforms = See [[μClinux#Supported architectures|below]]
}}
[[File:Linux kernel System Call Interface and uClibc.svg|thumb|300px|[[uClibc]] is a wrapper around the [[system call]]s of the [[Linux kernel]] and/or μClinux.]]

'''μClinux''' is a variation of the [[Linux kernel]], previously maintained as a [[Fork (software development)|fork]], that targets [[microcontroller]]s without a [[memory management unit]] (MMU).<ref>{{cite web|url=http://www.uclinux.org/description/|title=uClinux Description|access-date=2007-12-31|author=D. Jeff Dionne|author2=Michael Durrant|url-status=live|archive-url=https://web.archive.org/web/20071225125038/http://www.uclinux.org/description/|archive-date=2007-12-25}}</ref> It was integrated into the [[Mainline Linux|mainline kernel]] as of 2.5.46;<ref>{{cite web|url=http://www.ucdot.org/article.pl?sid=02/11/05/0324207|title= uClinux mainline Announcement|access-date=2008-01-15|author=Greg Ungerer|archive-url=https://web.archive.org/web/20071031135123/http://www.ucdot.org/article.pl?sid=02/11/05/0324207|archive-date=2007-10-31}}</ref> the project continues to develop patches and tools for microcontrollers. The homepage lists Linux kernel releases for 2.0, 2.4 and 2.6 (all of which are [[End-of-life (product)|end-of-life]] in mainline).

The letters "μC" are for "microcontroller": the name is pronounced "you-see-Linux", rather than pronouncing the letter [[Mu (letter)|mu]] as in [[Greek language|Greek]].<ref name="uclinuxmainpage">{{Cite web|url=http://www.uclinux.org/|title=μClinux|access-date=August 31, 2015|url-status=live|archive-url=https://web.archive.org/web/20061004015712/http://www.uclinux.org/|archive-date=October 4, 2006}}</ref>

== History ==
μClinux was originally created by D. Jeff Dionne and Kenneth Albanowski in 1998. Initially, they targeted the [[Motorola]] [[Freescale DragonBall|DragonBall]] family of embedded [[68k]] processors (specifically the 68EZ328 series used in the 3Com [[PalmPilot]]) on a 2.0.33 Linux kernel. After releasing their initial work, a developer community quickly sprang up extending their work to newer kernels and other microprocessor architectures. In early 1999, support was added for the Motorola (now NXP) [[Freescale ColdFire|ColdFire]] family of embedded microprocessors. [[ARM architecture|ARM]] processor support was added later.

Although originally targeting 2.0 series Linux kernels, it now has ports based on Linux 2.4 and Linux 2.6. The Linux 2.4 ports were forward ported from the 2.0.36 Linux kernel by Michael Leslie and Evan Stawnyczy during their work at Rt-Control. There were never any μClinux extensions applied to the 2.2 series kernels.

Since version 2.5.46 of the Linux kernel, the major parts of μClinux have been integrated with the mainline kernel for a number of processor architectures.<ref>Miles Gillham [https://www.linux.com/news/uclinux-and-linux-set-merge "uClinux and Linux set to merge"], ''[[Linux.com]]'', November 19, 2002.</ref>

Greg Ungerer (who originally ported μClinux to the Motorola ColdFire family of processors) continued to maintain and actively push core μClinux support into the 2.6 series Linux kernels. In this regard, μClinux is essentially no longer a separate fork of Linux.

μClinux had support for many architectures, and forms the basis of many products, like [[Router (computing)|network routers]], security cameras, [[DVD player|DVD]] or [[Digital audio player|MP3 players]], [[Voice over Internet Protocol|VoIP]] phone or gateways, [[Image scanner|scanners]], and card readers.

Support for several of the original target architectures was dropped in 2018.<ref>Linus Torvalds [https://lkml.org/lkml/2018/4/15/201 "Linux 4.17-rc1"], ''[[LKML.ORG]]'', 15 April 2018.</ref> The obsolete CPU architectures set to be removed in Linux 4.17 and subsequent releases included ADI Blackfin, Etrax CRIS, Fujitsu FR-V, Mitsubishi M32R, Matsushita/[[Panasonic]] [[MN10300]], [[Imagination META]] (Metag), and [[Tilera]] TILE.<ref>Jonathan Corbet [https://lwn.net/Articles/748074 "Shedding old architectures and compilers in the kernel"], ''[[LWN.net]]'', February 26, 2018.</ref>

===Hardware projects===
The leanXCam{{anchor|leanXcam}} was an [[open source|open-source]] [[Computer programming|programmable]] [[smart camera]] used for industrial applications in the field of [[machine vision]] that ran under μClinux; the camera won an award at the 2008 VISION tradeshow.<ref>{{cite news
  | editor-last  = Wilson
  | editor-first = Andrew
  | date         = Jan 2009
  | title        = Open-source system wins VISION Award
  | url          = https://www.proquest.com/docview/224134687
  | url-access   = subscription
  | work         = Vision System Design
  | volume       = 14
  | issue        = 1
  | pages        = 11–12, 15
  | access-date  = 2023-11-29
| id = {{ProQuest|224134687}}
 }}</ref> As of 2015, the project was discontinued.<ref>{{Cite web |title=home |url=https://github.com/scs/leanXcam/wiki/home |access-date=2023-11-29 |website=GitHub |language=en}}</ref>

== Supported architectures ==
The current list includes:
* [[Altera]] [[Nios embedded processor|Nios]]/[[Nios II]]
* [[Amber (processor core)|Amber]] (open FPGA core)
* [[ARM architecture|ARM]] [[ARM7TDMI]], [[ARM Cortex-M|ARM Cortex-M3/M4/M7]],<ref>{{cite web |title=Linux for ARM® Processors www.arm.com Summer/Winter 2013 Robert Boys System Design Division, ARM |date=2013-09-10 |access-date=2014-07-17 |url=http://www.sase.com.ar/2013/files/2013/09/SASE2013-Linux-BobBoys.pdf |quote=What about Cortex-M and Cortex-R ? /../ These can run a modified version of Linux called uClinux.}}</ref> [[ARM Cortex-R]]
* [[Lattice Semiconductor|Lattice]] [[LatticeMico32|Mico32]]
* [[NXP]] [[Motorola 68000 series|680x0]] (Motorola/Freescale 680x0)
* [[Hyperstone]] E1/E2 (called hyLinux)
* [[Intel i960]]
* [[MIPS architecture|MIPS]]
* [[NXP ColdFire]] (Motorola/Freescale ColdFire)
* [[Xilinx]] [[MicroBlaze]]

=== No longer supported ===
* [[NEC V850E]] - removed in Linux 2.6.27.<ref>{{Cite web |url=https://kernelnewbies.org/Linux_2_6_27#head-b14ab696e23019ae4b6362c5816bcd23a55240ce |title=Linux 2.6.27 kernel released 9 October 2008 |accessdate=2023-12-13}}</ref><ref>{{ cite web |url=https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f606ddf42fd4edc558eeb48bfee66d2c591571d2 |title=remove the v850 port}}</ref>
* [[Hitachi, Ltd.|Hitachi]]/[[Renesas]] [[H8 Family|H8]] (<kbd>h8300</kbd>) - removed in Linux 5.19.<ref>{{Cite web |url=https://kernelnewbies.org/Linux_5.19#H8300 |title=Linux 5.19 was released on Sunday, 31 Jul 2022. |accessdate=2023-12-24}}</ref><ref>{{ cite web |url=https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1c4b5ecb7ea190fa3e9f9d6891e6c90b60e04f24 |title=remove the h8300 architecture}}</ref>

Before Linux 4.17 the following architectures were also supported:<ref>{{cite web |url=http://lkml.iu.edu/hypermail/linux/kernel/1804.0/00306.html |title=[GIT PULL] arch: remove obsolete architecture ports}}</ref>
* [[Analog Devices|ADI]] [[Blackfin]] (<kbd>blackfin</kbd>)
* [[Axis Communications|Axis]] [[ETRAX CRIS|ETRAX]] (<kbd>cris</kbd>)
* [[Fujitsu]] [[FR-V]] (<kbd>frv</kbd>)
* [[Mitsubishi]]/Renesas [[M32R]] (<kbd>m32r</kbd>)

== References ==
{{Reflist}}

== External links ==
* {{github|uclinux-dev}}
*{{webarchive |url=https://web.archive.org/web/20181113230737/http://www.uclinux.org/pub/uClinux/dist/ |title=μClinux-dist, complete source ''distribution package''}}
* {{sourceforge|uclinux}}
* {{webarchive |url=https://web.archive.org/web/20170324024708/http://retired.beyondlogic.org/uClinux/uClinux.htm |title=μClinux - Setting up the Development Environment}}
* {{github|AcceleratedLinux/accelerated-linux}}, an actively developed continuation<ref>[https://events19.linuxfoundation.org/wp-content/uploads/2017/12/BoF-Accelerated-Linux-Build-System-Jeff-Shaw-Digi-International.pdf BoF- Accelerated Linux Build System - Jeff Shaw, Digi International]</ref> of μClinux ''distribution package'' by [[Digi International|Digi]]
{{Linux kernel}}

{{DEFAULTSORT:UClinux}}
[[Category:ARM operating systems]]
[[Category:MIPS operating systems]]
[[Category:Embedded Linux]]
[[Category:Embedded operating systems]]
[[Category:Lightweight Unix-like systems]]
[[Category:Linux kernel]]