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=dead|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 (2007) in the form of a NOMMU option.<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>

After the mainline merge, the μClinux project continued to develop patches and tools for microcontrollers. The last [[Wayback Machine]] archive of the homepage (from 2018) 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, 2.6 being the last to go in 2016), with the last news entry dated May 2016 concerning a new release of the kernel distribution. The website remained unchanged through 2021, when it went offline.<ref name=hp18>{{webarchive |url=https://web.archive.org/web/20181113230737/http://www.uclinux.org/ |title=uclinux.org}}</ref>

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.

=== 2010s ===
The volume of mails on the μClinux [[mailing list]] greatly decreased in the 2010s, with very few months producing more than 100 KB of mail in total.<ref name=mail21>{{cite web |title=The uClinux-dev Archives |url=https://web.archive.org/web/20210519232107/http://mailman.uclinux.org/pipermail/uclinux-dev/ |website=mailman.uclinux.org}}</ref>
{{Chart| chart = Uclinux mailinglist traffic.Line.chart}}

The Linux kernel upstream marked version 2.6 as end-of-life in February 2016. The last "uclinux-dist", a distribution package containing the source code of the patched kernel, was released on SourceForge September 2016. It contained not only 2.6 but also those based on newer upstream versions 3.x and 4.x. The last update of most tools on SourceForge also date back to February and September 2016.<ref name="sf-files">{{cite web |title=uClinux - Browse Files at SourceForge.net |url=https://sourceforge.net/projects/uclinux/files/ |website=sourceforge.net}}</ref>

Support for several of the original target architectures was dropped in April 2018 by the Linux upstream.<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>

The homepage was last seen updated in 2018 per Wayback Machine.<ref name=hp18/> Tools for arm-linux-gnueabi and mips64 were updated in 2018.<ref name="sf-files"/>

=== 2020s ===
The last accessible archives of the project's website date to 2021. The website has presumably went offline after this point.<ref name=mail21/>

The [[GitHub]] page of the project continued to receive occasional updates, with the elf2flt tool last updated in August 2024.<ref name=GH>{{cite web |title=μClinux |url=https://github.com/uclinux-dev |website=GitHub |access-date=17 December 2025 |language=en}}</ref> The [[SourceForge]] page was last updated in 2023, a with new tool build for m68k.<ref name="sf">{{cite web |title=uClinux |url=https://sourceforge.net/projects/uclinux/ |website=SourceForge |access-date=17 December 2025 |language=en |date=27 October 2023}}</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>
* [[Analog Devices|ADI]] [[Blackfin]] (<kbd>blackfin</kbd>) &ndash; removed in 4.17<ref name=r417>{{cite web |url=http://lkml.iu.edu/hypermail/linux/kernel/1804.0/00306.html |title=[GIT PULL] arch: remove obsolete architecture ports}}</ref>
* [[Axis Communications|Axis]] [[ETRAX CRIS|ETRAX]] (<kbd>cris</kbd>) &ndash; removed in 4.17<ref name=r417/>
* [[Fujitsu]] [[FR-V]] (<kbd>frv</kbd>) &ndash; removed in 4.17<ref name=r417/>
* [[Mitsubishi]]/Renesas [[M32R]] (<kbd>m32r</kbd>) &ndash; removed in 4.17<ref name=r417/>
* [[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>

==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>

== 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]]