Editing SYSLINUX

{{Short description|Bootloader suite for Linux operating system}}
{{Primary sources|date=July 2008}}

{{Infobox software
| screenshot             = SysLinux.png
| caption                = Screenshot of SYSLINUX
| developer              = [[H. Peter Anvin]]
| latest release version = 6.03
| latest release date    = {{Start date and age|2014|10|6}}
| latest preview version = 6.04-pre3
| latest preview date    = {{Start date and age|2019|02|07}}
| operating system       = [[Linux]]
| genre                  = Boot loader
| license                = [[GNU General Public License|GPL-2.0-or-later]]
| website                = {{URL|https://www.syslinux.org}}
}}

'''The Syslinux Project''' is a discontinued suite of five different [[bootloader]]s for starting up [[Linux distribution]]s on computers. It was primarily developed by [[Hans Peter Anvin|H. Peter Anvin]].

==Components==
The Syslinux Project consists of five different bootloaders:

* The eponymous SYSLINUX, used for booting from the [[File Allocation Table|FAT]] filesystem
* ISOLINUX, used for booting from the [[ISO 9660]] file system{{sfn|Negus|2006|p=133}}
* PXELINUX, used for booting from a network server using the [[Preboot Execution Environment]] (PXE) system{{sfn|Negus|2006|p=133}}
* EXTLINUX, used for booting from [[Btrfs]], [[ext2]], [[ext3]], [[ext4]], [[File Allocation Table|FAT]], [[NTFS]], [[Unix File System|UFS/UFS2]], and [[XFS]] filesystems
* MEMDISK, emulates a [[RAM disk]] for older operating systems like [[MS-DOS]]

The project also includes two separate menu systems and a development environment for additional modules.

==={{Anchor|ISOLINUX}}SYSLINUX and ISOLINUX===
SYSLINUX was originally meant for rescue [[floppy disk]]s, [[live USB]]s, or other lightweight environments. ISOLINUX is meant for [[live CD]]s and Linux installation CDs.

The SYSLINUX bootloader can be used to boot multiple distributions from a single source such as a USB stick.{{Sfn|Pakrashi|2009|pp=66, 71−73}}

A minor complication is involved when booting from [[compact disc]]s. The [[El Torito (CD-ROM standard)|El Torito standard]] allows booting in two different modes:

* ''No emulation''{{snd}} Requires storing the boot information directly on the CD. ISOLINUX is suitable for this mode.
* ''Floppy emulation''{{snd}} Requires storing the boot information in a [[disk image]] file suitable for emulating a [[File Allocation Table|FAT]]-formatted floppy disk. SYSLINUX is suitable for this mode.

To have this choice is sometimes useful, since ISOLINUX is vulnerable to [[BIOS]] bugs.{{which|date=September 2020}} For that reason, it is handy to be able to boot using SYSLINUX. This mostly affects computers built before about 1999, and, in fact, for modern computers the "no emulation" mode is generally the more reliable method. Since version 3.72 ISOLINUX supports the creation of so-called "hybrid ISO" images, that put both the ''El Torito'' boot record of the compact discs and the [[master boot record]] of [[hard disk]]s into an ISO image . This hybrid image could then be written to both a compact disc or a USB flash drive.<ref>{{cite web | url=https://repo.or.cz/syslinux.git/blob/HEAD:/doc/isolinux.txt | title=syslinux/doc/isolinux.txt | date=2011-05-04 | access-date=2019-02-23}}</ref>

===PXELINUX===
PXELINUX is used in conjunction with a [[Preboot Execution Environment|PXE]]-compliant [[Read-only memory|ROM]] on a [[network interface controller]] (NIC), which enables receiving a [[booting|bootstrap program]] over the [[local area network]].{{sfn|Bresnahan|Blum|2019|pp=136–137}} This bootstrap program loads and configures an [[operating system kernel]] that puts the user in control of the computer.<ref>{{cite web  |url = https://repo.or.cz/syslinux.git/blob/HEAD:/doc/pxelinux.txt |title  = syslinux/doc/pxelinux.txt |date = 2014-02-01 |accessdate  = 2019-02-23}}</ref> Typically, PXELINUX is used for performing Linux installations from a central network server or for booting [[Diskless node|diskless workstations]].

===EXTLINUX===
EXTLINUX is a general-purpose bootloader, similar to [[LILO (boot loader)|LILO]] or [[GNU GRUB|GRUB]]. Since Syslinux 4, EXTLINUX is capable of handling [[Btrfs]], [[File Allocation Table|FAT]], [[NTFS]], [[Unix File System|UFS/UFS2]], and [[XFS]] filesystems.

==COMBOOT==
SYSLINUX can be extended by COMBOOT modules written in [[C (programming language)|C]] or [[Assembly Language|assembly language]]. 32-bit modules typically use the <code>.c32</code> [[filename extension]]. Version 5 and later do not support 16-bit <code>[[COM file|.com]]</code> modules.<ref>{{cite web
|url=https://www.syslinux.org/archives/2012-December/019050.html
|title=Syslinux 5.00 released
|work=Syslinux mailing list
|author=Matt Fleming
|date=2012-12-06
|accessdate=2019-02-23}}</ref>

==={{Anchor|HDT}}Hardware Detection Tool (HDT)===
Since the 3.74 release, the Syslinux project hosts the Hardware Detection Tool (HDT) project, licensed under the terms of [[GNU GPL]]. This tool is a 32-bit module that displays low-level information for any [[IA-32]]–compatible system.  It provides both a command-line interface and a semi-graphical menu mode for browsing.  HDT is also available as a bootable ISO and a 2.88&nbsp;MB floppy disk image. The last update of HDT was in 2015; it has since been discontinued.<ref>{{Sourceforge|hdt|Hardware Detection Tool}}</ref>

==See also==
{{Portal|Free and open-source software}}
* [[Comparison of bootloaders]]

==References==
{{Reflist}}

==Sources==
* {{cite book|last1=Bresnahan|first1=Christine|last2=Blum|first2=Richard|date=11 July 2019|title=CompTIA Linux+ Study Guide — Exam XK0-004
        |publisher=Wiley|location=United Kingdom|isbn=9781119556039|oclc=1066596041}}
* {{Cite AV media|last1=Murphy|first1=Mike|date=4 April 2017a|title=Slackware Linux: Syslinux Bootloader
        |url=https://www.youtube.com/watch?v=bgydvZnEk5o |archive-url=https://ghostarchive.org/varchive/youtube/20211221/bgydvZnEk5o |archive-date=2021-12-21 |url-status=live|access-date=17 August 2021|via=[[YouTube]]}}{{cbignore}}
* {{cite book|last=Negus|first=Christopher|date=2006|title=Live Linux CDs: Building and Customizing Bootables
        |publisher=Prentice Hall|isbn=0-13-243274-9|oclc=846108594}}
* {{Cite magazine|last=Pakrashi|first=Arjun|date=August 2009|title=Create Multi-boot Discs
        |magazine=Linux For You|volume=7|issue=6|pages=66–73|location=Delhi|issn=0974-1054|publisher=Ramesh Chopra|editor=Rahul Chopra}}

==External links==
* [https://kernel.org/pub/linux/utils/boot/syslinux/ SYSLINUX releases]
* [https://lists.zytor.com/syslinux Mailing list]

{{Linux}}
{{Linux kernel}}

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[[Category:Free boot loaders]]
[[Category:Linux software]]
[[Category:Linux-only free software]]