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{{For|the Emergency lane keeping system (ELKS)|Lane departure warning system}}
The '''Embeddable Linux Kernel Subset (ELKS)''' is a [[Unix-like]] operating system [[kernel (computer science)|kernel]] that can run on [[Intel 8086]]-compatible [[microprocessor]]s. ELKS, formerly known as ''Linux-8086'', is a small subset of [[Linux (kernel)|Linux]] and can run on machines with limited processor and memory resources, including machines with [[16-bit]] microprocessors that are not supported by Linux.
{{primary sources|date=March 2024}}
{{Infobox OS
| name = ELKS
| logo = ELKS logo.svg
| family = [[Unix-like]]
| released = 0.0.76 ({{Start date and age|1999|05|20|df=yes}})
| latest release version = {{wikidata|property|preferred|references|edit|Q1331667|P348|P548=Q2804309}}
| latest release date = {{Start date and age|{{wikidata|qualifier|preferred|single|Q1331667|P348|P548=Q2804309|P577}}}}
| language = [[English language|English]]
| kernel type = [[Monolithic kernel|Monolithic]]
| license = [[GPL v2]]<ref>{{cite web |url=https://github.com/ghaerr/elks/blob/master/LICENSE |title=LICENSE file on github|website=[[GitHub]] }}</ref>
}}
The '''Embeddable Linux Kernel Subset''' ('''ELKS'''), formerly known as '''Linux-8086''', is a [[Linux-like]] operating system [[kernel (operating system)|kernel]]. It is a subset of the [[Linux kernel]], intended for [[16-bit]] computers with limited processor and memory resources such as machines powered by [[Intel 8086]] and compatible [[microprocessor]]s not supported by [[32-bit]] [[Linux]].<ref>{{Cite book|title=Building embedded Linux systems|date=2008|publisher=O'Reilly Media|others=Karim Yaghmour|isbn=978-0-596-52968-0|edition=2nd|___location=Sebastopol [Calif.]|pages=7|oclc=273049576}}</ref><ref>{{Cite book|last=Danesh|first=Arman|title=MasteringTM Linux.|date=2006|publisher=John Wiley & Sons|others=Michael Jang|isbn=978-0-7821-5277-7|edition=2nd|___location=Hoboken|pages=904|oclc=437171498}}</ref>
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==Features and compatibility==
ELKS is [[free software]] and is available under the [[GNU General Public License]] (GPL).
ELKS is [[free software]] and available under the [[GNU General Public License]] (GPL). It can work with early [[16-bit]] (e.g. 8086, [[Intel 8088|8088]]) and many [[32-bit]] [[x86]] computers like [[IBM PC compatible]] systems, and later x86 models in [[real mode]]. Another useful area is [[single-board computer|single board microcomputers]], intended as educational tools for "[[wikt:homebrew|homebrew]]" projects (hardware [[Hacker (hobbyist)|hacking]]), as well as embedded controller systems (e.g. [[Automation]]).<ref name="Intro">[https://elks.sourceforge.net/introduction.html Introduction to ELKS]</ref>
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Early versions of ELKS also ran on [[Psion Series 3#Psion Series 3a|Psion 3a]] and 3aR [[EPOC (operating system)#EPOC16|SIBO]] (SIxteen Bit Organiser) [[Personal Digital Assistant|PDA]]s with NEC [[NEC V20#Variants and successors|V30]] CPUs,<ref name="Intro"/><ref>{{cite web |url=http://www.elks.ecs.soton.ac.uk/sibo.php3 |title=Information on SIBO |accessdate=2014-03-02 |url-status=bot: unknown |archiveurl=https://web.archive.org/web/20011021222654/http://www.elks.ecs.soton.ac.uk/sibo.php3 |archivedate=October 21, 2001 }}</ref> providing another possible field of operation ([[gadget]] hardware), if ported to such a platform. This effort was called ELKSibo.<ref>{{cite web |url=http://www.mungewell.ndirect.co.uk/linux/ |title=Information on ELKSibo |accessdate=2014-03-02 |url-status=bot: unknown |archiveurl=https://web.archive.org/web/20050327202617/http://www.mungewell.ndirect.co.uk/linux/ |archivedate=March 27, 2005 }}</ref> Due to lack of interest, SIBO support was removed from version 0.4.0.
 
Native ELKS programs may run [[Emulator|emulated]] with Elksemu, allowing 8086 code to be used under Linux-i386.<ref>[http://linux.die.net/man/1/elksemu Elksemu man page]</ref> An effort to provide ELKS with an [[Eiffel (programming language)|Eiffel]] compliant [[Library (computing)|library]] also exists.<ref>[https://sourceforge.net/projects/freeelks/ Implementation of ELKS Eiffel library]</ref>
 
==History==
Development of Linux-8086 started in 1995 by Linux kernel developers [[Alan Cox (computer programmer)|Alan Cox]] and Chad Page as a [[fork (software development)|fork]] of the standard Linux. By early 1996 the project was renamed ELKS (Embeddable Linux Kernel Subset), and in 1997 the first website<ref>{{Cite web |url=http://www.elks.ecs.soton.ac.uk/ |title=ELKS pages |access-date=November 16, 2006 |archive-date=September 24, 2001 |archive-url=https://web.archive.org/web/20010924210617/http://www.elks.ecs.soton.ac.uk/ |url-status=dead }})</ref> was created. ELKS version 0.0.63 followed on August 8 that same year. On June 22, 1999, ELKS release 0.0.77 was available, the first version able to run a [[graphical user interface]] (the [https://www.microwindows.org/ Nano-X Window System]). On July 21, ELKS booted on a [[Psion PLC|Psion]] PDA with SIBO architecture. ELKS 0.0.82 came out on January 10, 2000. By including the SIBO [[Porting|port]], it became the first official version running on other [[computer hardware]] than the original 8086 base. On March 3 that year, the project was registered on [[SourceForge]].<ref>[http://elks.sourceforge.net elks.sourceforge.net]</ref>
{{Prose|date=September 2008}}
 
* 1995 - Development of Linux-8086 by Linux kernel developers [[Alan Cox]] and Chad Page starts as a [[fork (software development)|fork]] of the standard Linux.
On January 6, 2001, Cox declared ELKS "basically dead".<ref>January 6, 2001, {{cite web |url=https://sourceforge.net/forum/forum.php?forum_id=56220 |title=status update by Alan Cox |accessdate=2006-11-16 |url-status=bot: unknown |archiveurl=https://web.archive.org/web/20010920200533/http://sourceforge.net/forum/forum.php?forum_id=56220 |archivedate=September 20, 2001 }}</ref> Nonetheless, release 0.0.84 came along on June 17, 2001, Charilaos (Harry) Kalogirou added TCP/IP networking support seven days later, and in the same year ELKS reached 0.0.90 on November 17. On April 20, 2002, Kalogirou added [[memory management]] with [[disk swapping]] capability, followed nine days later by ELKS release 0.1.0, considered the first [[Development stage#Beta|beta version]].<ref name="Rel_Info_old">{{Cite web |url=https://sourceforge.net/p/elks/news/ |title=Older release information, e.g. on ELKS 0.1.0, the first Beta |access-date=2014-03-02 |archive-url=https://web.archive.org/web/20140316152219/http://sourceforge.net/p/elks/news/ |archive-date=2014-03-16 |url-status=dead }}</ref> By end of the year, on December 18, the EDE (Elks Distribution Edition, a distribution based on the ELKS kernel), itself version 0.0.5, is released.<ref>[https://lwn.net/Articles/18400/ Announce of the EDE 0.0.5 release]</ref> January 6, 2003, brought ELKS 0.1.2, an update to 0.1.3 followed on May 3, 2006, the first official release after a long hiatus in development.<ref name="Rel_Info_old" />
* Early 1996 - The project is renamed ELKS, Embeddable Linux Kernel Subset.
 
* 1997 - The first website http://www.elks.ecs.soton.ac.uk/ (now offline, [http://web.archive.org/web/20020119145412/elks.sourceforge.net/ archived version]) is created.
A development into FlightLinux, a [[Real-time computing|real-time]] operating system for [[spacecraft]], was planned, but the project it was intended for ([[UoSAT-12]]) eventually settled on the qCF operating system from Quadron Corporation instead.<ref>[http://www.spinics.net/lists/linux-8086/msg00264.html Linux-8086: Flight Linux]</ref>
* August 8, 1997 - ELKS 0.0.63 is released.
* June 22, 1999 - ELKS 0.0.77 is released. This version is the first that is able to run a [[graphical user interface]] (the [http://www.microwindows.org/ Nano-X Window System]).
* July 21, 1999 - ELKS boots on a [[Psion 3#Psion 3a and Psion 3aR|Psion 3a]] [[Personal digital assistant|PDA]] ([[EPOC (computing)#EPOC16|SIBO]] architecture).
* January 10, 2000 - ELKS 0.0.82 is released, the first official version which includes the SIBO [[Porting|port]].
* March 3, 2000 - The [http://sourceforge.net/projects/elks/ ELKS project] is registered on [[SourceForge]], the new website is http://elks.sourceforge.net/.<ref>[http://sourceforge.net/projects/elks/ SourceForge ELKS project page]</ref>
* January 6, 2001 - Alan Cox declares the project "basically dead".<ref>January 6, 2001 [http://web.archive.org/web/20010920200533/http://sourceforge.net/forum/forum.php?forum_id=56220 project status update] from Alan Cox (archived)</ref>
* June 17, 2001 - ELKS 0.0.84 is released.
* June 24, 2001 - Charilaos Kalogirou adds TCP/IP networking support.
* November 17, 2001 - ELKS 0.0.90 is released
* April 20, 2002 - Charilaos Kalogirou adds virtual memory support with disk swapping capability.
* April 29, 2002 - ELKS 0.1.0 is released, this is the first [[Development stage#Beta|beta version]].<ref>[http://sourceforge.net/project/showfiles.php?group_id=3232&package_id=3148&release_id=87385 ELKS 0.1.0, the first beta version]</ref>
* December 18, 2002 - EDE (the Elks Distribution Edition, a distribution based on the ELKS kernel) version 0.0.5 is released.<ref>[http://lwn.net/Articles/18400/ Announce of the EDE 0.0.5 release]</ref>
* January 6, 2003 - ELKS 0.1.2 is released.<ref name="officialsite">[http://elks.sourceforge.net/ Official ELKS website]</ref>
* May 3, 2006 - ELKS 0.1.3 is released, the first official release after a long hiatus in development.<ref>[http://sourceforge.net/project/showfiles.php?group_id=3232&package_id=3148&release_id=414456 ELKS 0.1.3, currently the last released version]</ref>
* February 19, 2012 - ELKS 0.1.4 is released, this version fix compilation BUGs from 0.1.3 and remove unused codes. This version is in memory of Riley Williams<ref>[http://www.spinics.net/lists/linux-8086/msg00404.html]</ref>
More than 30 developers have contributed to this project since the Linux fork.
 
==Current status and usage==
Since January 2012 ELKS is again under development. The CVS [[software repository|repository]] was migrated to [[Git (software)|Git]] in February 2012, and numerous patches from the Linux-8086 mailing list were committed to the new repository. Version 0.1.4 came out on February 19, 2012, released by Jody Bruchon in memory of Riley Williams, a former co-developer. It included updated floppy [[disk image]]s, fixing compilation bugs of the previous version and removing unused codes.<ref>{{Cite web |url=http://www.spinics.net/lists/linux-8086/msg00404.html |title=ELKS release 0.1.4 |access-date=2012-02-19 |archive-url=https://web.archive.org/web/20120221140352/http://www.spinics.net/lists/linux-8086/msg00404.html |archive-date=2012-02-21 |url-status=dead }}</ref> On May 10, 2012, BusyELKS was added to the repository by Jody Bruchon in an attempt to replace stand-alone [[binaries]] and to take advantage of shared code (ELKS does not support [[Library (computing)#Shared libraries|shared libraries]]). [[BusyBox]]-like binaries attempt to save space with symbolic links, eliminating redundant chunks of code, and are combining separate programs into one bigger binary.<ref>[https://github.com/ghaerr/elks/tree/master/elkscmd/busyelks BusyELKS introduction]</ref> On November 14, 2013, project development moved to [[GitHub]].<ref>[http://www.spinics.net/lists/linux-8086/msg00500.html Info on ELKS' GitHub move]</ref> Rudimentary Ethernet and FAT support were added in 2017.<ref>{{Cite web|url=https://www.spinics.net/lists/linux-8086/msg00748.html|title=ELKS is now Ethernet capable — Linux for 8086|website=www.spinics.net|access-date=2018-06-25}}</ref>
As of January 2012, ELKS is under sporadic development. The CVS repository was migrated to Git in February 2012, and numerous patches from the Linux-8086 mailing list were committed to the ELKS Git repository. The latest released version is 0.1.3<ref name="officialsite"/>(Gzip file of 0.1.3 is corrupted, but 0.1.1 is still working and available) and the latest EDE version is 0.0.5b.<ref>[http://sourceforge.net/project/showfiles.php?group_id=3232&package_id=68748 EDE SourceForge download page]</ref> Some of the patches committed to the Git repository include fixes for 0.1.3 that make ELKS compile properly.
 
More than 35 developers have contributed to this project since the fork in 1995. As of March 2015, development of the ELKS project was again active, reaching a milestone 1,000 [[source code]] commits on March 8, 2015. As of June 2018, many bug fixes and improvements were performed with 583 more commits, leading to the 0.2.1 release. In March 2019, the project completed its transition from the obsolete [[Borland C++|BCC]] compiler to the more recent GCC-IA16 ([[GNU Compiler Collection]]-[[List_of_Intel_CPU_microarchitectures#16-bit|Intel Architecture 16]]), and development activity increased as [[Gregory Haerr]] took the helm as lead developer. During 2019 and 2020 ELKS moved from a 'bootable, unstable' status to a stable Linux-like system for small machines with Ethernet, TCP/IP, FAT16/32, multiuser serial and many more functions.<ref>{{Cite web|title=ELKS v0.4.0 Pre-release version history and credits · Issue #873 · ghaerr/elks|url=https://github.com/ghaerr/elks/issues/873|access-date=2021-04-09|website=GitHub|language=en}}</ref> As ELKS 0.4.0 was released in November 2020, the number of commits had passed 3,000.
ELKS runs on [[IBM PC compatible]] systems and on [[Psion PLC|Psion]] SIBO PDAs. It was planned to be developed into the [[FlightLinux]] [[Real-time computing|real-time]] operating system for [[spacecraft]]s, but the project it was intended for ([[UoSAT-12]]) eventually settled on the qCF operating system from Quadron Corporation instead.<ref>[http://www.spinics.net/lists/linux-8086/msg00264.html Linux-8086: Flight Linux]</ref>
 
Building on the foundation created by 0.4.0, development activity continued during 2021, still with Gregory Haerr as lead developer, supported by 5 active contributors. The team delivered 220 commits from October 2021 to 0.5.0 release on February 8, 2022.<ref>{{Cite web|title=Release ELKS v0.5.0 · ghaerr/elks|url=https://github.com/ghaerr/elks/releases/tag/v0.5.0|access-date=2022-02-09|website=GitHub|language=en}}</ref> Four months later, on Jun 7th 2022, 0.6.0 was released, setting a new level or release frequency and indicating a very high level of activity.<ref name=":0">{{Cite web |title=Release ELKS v0.6.0 · ghaerr/elks |url=https://github.com/ghaerr/elks/releases/tag/v0.6.0 |access-date=2022-06-17 |website=GitHub |language=en}}</ref>
==See also==
 
== Version 0.4.0 ==
{{Portal|Free software}}
Version 0.4.0 represented a major milestone for ELKS, lifting the system from experimental to useful for non-developers, and included the following major enhancements:
 
* Documentation Wiki<ref>{{Cite web|title=ELKS wiki|url=https://github.com/ghaerr/elks/wiki|access-date=2021-04-09|website=GitHub|language=en}}</ref>
* [[IBM Personal Computer]]
* Major kernel enhancements – size, stability, robustness, speed, system calls and debugging features.
* [[Psion 3]]
* Reliable [[Internet protocol suite|TCP/IP]] stack implemented as a user mode process, supporting TCP, [[Internet Control Message Protocol|ICMP]], [[Address Resolution Protocol|ARP]].
* User level networking support for [[telnet]]/telnetd and file transfer.
* [[Serial Line Internet Protocol|Serial IP]] and [[Ethernet]] (NE1K/[[Ne2k|NE2K]]/WD8003) support.
* Many new and updated user level commands, including [[Almquist shell|ash]] and [[Stand-alone shell|sash]] [[Unix shell|shells]].
* Many cross development tool-chain enhancements supporting more memory models, easing porting of more applications.
* Robust [[FAT16]]/32 and [[MINIX file system|Minix1]] file system support, including booting from /root on FAT file systems.
* Improved console and [[Serial port|serial]] support: Serial console, high speed multiple serial I/O.
* [[Master boot record|MBR]] support, boot options via /bootopts.
* Updated menu-system for configuration and building on Linux and MacOS, allowing non-developers to build custom images for floppies ranging from 360KB to 2.88MB.
 
== Version 0.5.0 ==
Version 0.5.0 was another significant milestone for ELKS with a number of important improvements, additions and support for 2 new platforms - the Japanese [[PC-9800 series|PC-98]] and [[Intel 80186|80186/80188]]. Enhancements included:<ref>{{Cite web|title=Release ELKS v0.5.0 · ghaerr/elks|url=https://github.com/ghaerr/elks/releases/tag/v0.5.0|access-date=2022-02-09|website=GitHub|language=en}}</ref>
 
* Kernel and network debugging tools, [[toolchain]] improvements, cleanups to ease porting to new platforms
* Network stack stability and performance improvements
* Native ftp/ftpd programs, expanding network application level protocol support to [[telnet]], [[File Transfer Protocol|ftp]], [[Hypertext Transfer Protocol|http]] and raw tcp ([[netcat]])
* Improved runtime configuration via /bootopts configuration file,
* [[XMS (memory management)|XMS]]-support for [[80386|386]] and [[80286|286]] systems, enabling high memory buffers
* New [[Solid-state drive|SSD]] driver
* Support for compressed executables<ref>{{Cite web|title=[kernel] Implement compressed executables in ELKS by ghaerr · Pull Request #912 · ghaerr/elks|url=https://github.com/ghaerr/elks/pull/912|access-date=2021-04-10|website=GitHub|language=en}}</ref>
* Support for very low memory environments (256k)
* Library and [[system call]] enhancements
* Kernel support for variable [[disk sector|sector]] sizes (for [[PC-98]] platform)
* New startup configuration files for networking and mass storage
* Improved networking support when running in [[QEMU]]
 
As of version 0.5.0 ELKS is a complete small-Linux system and a versatile tool for testing, diagnosing and running vintage PCs with limited resources. The improved portability demonstrated by the addition of new platforms, paves the way for increased development activity towards the next version.
 
== Version 0.6.0 ==
Released on June 7, 2022, 0.6.0 defined a new level for ELKS, as indicated by the much shorter than usual release cycle. The speed at which the system evolves and improves, combined with its recently acquired reliability and usability created a demand for 'updated packaged releases' from new users.
 
0.6.0 included lots of enhancements and optimizations on both system and application level. New additions included:<ref name=":0" />
 
* [[BASIC]] interpreter with demo programs
* Manual pages
* Expanded support for the new platforms - [[PC-9800 series|PC98]] and [[Intel 80186|80186/80188]], notably SCSI and IDE drive support for the PC98
* Kernel, library and networking fixes/enhancements
* New commands, such as [[tar (computing)|tar]], [[man page|man]] and [[compress (software)|compress]]
 
200 commits were delivered by the team between the 0.5.0 and 0.6.0 release, more than half by Gregory Haerr.
 
== Version 0.7.0 ==
It was released on August 3, 2023.<ref>[https://github.com/ghaerr/elks/releases/tag/v0.7.0 ELKS v0.7.0 ]</ref>
 
==See also==
{{Portal|Free and open-source software}}
* [[TinyLinux]]
* [[μClinux]]
* [https://www.fuzix.org Fuzix OS], a Linux-like for ''[[8-bit]]'' architectures
 
==References==
{{Reflist|30em}}
<!--See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the <ref> and </ref> tags and the tag below -->
{{Reflist|2}}
 
==External links==
* [httphttps://elks.sourceforgesf.net/ Officialold ELKS websitepage]
* {{sourceforge|elks}}
* [http://homepage.ntlworld.com/robert.debath/ ELKS development tools]
* {{github|tkchia/gcc-ia16|Official ELKS development tools page}}
* [ftp://ftp.ecs.soton.ac.uk/pub/elks/ FTP site with old ELKS source files]
* {{github|ghaerr/elks/tree/master/elksemu|Elksemu, part of development tools}}
 
[[Category:Linux kernel]]
[[Category:Monolithic kernels]]
[[Category:Embedded Linux]]
[[Category:Computing timelines]]
[[Category:Lightweight Unix-like systems]]
 
[[cs:Embeddable Linux Kernel Subset]]
[[de:ELKS]]
[[pl:Embeddable Linux Kernel Subset]]