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The SYSLINUX Project covers a suite of lightweight bootloaders, for starting up computers in the Linux operating system. It is the work of H. Peter Anvin, and consists of several separate systems:
* the original SYSLINUX, used for booting from FAT filesystems (usually floppy discs);
* ISOLINUX, used for booting from CD-ROM ISO 9660 filesystems;
* PXELINUX, used for booting from a network server using the Pre-boot eXecution Environment (PXE) system;
* EXTLINUX, used to boot from Linux ext2/ext3 filesystems;
* MEMDISK, used to boot older operating systems like MS-DOS from these media;
* two separate menu systems; and
* a development environment for additional modules.
SYSLINUX is not normally used for booting full Linux installations since Linux is not normally installed on FAT filesystems. Instead, it is often used for boot or rescue floppy discs, or other lightweight systems. ISOLINUX is generally used by Linux LiveCD and bootable install CDs.
A minor complication is involved when booting from CD-ROM. The El Torito standard allows for booting in two different modes;
* floppy emulation mode where the boot information is stored in an image file of a floppy disc, which is loaded from the CD and then behaves as a virtual floppy disc. This image file is effectively a FAT filesystem, so SYSLINUX is the required bootloader.
* no emulation mode where the boot information is stored directly on the CD (not in a floppy image). In this mode ISOLINUX is required.
To have this choice is sometimes useful however as ISOLINUX is vulnerable to BIOS bugs, in which case it's handy to be able to boot using SYSLINUX. This mostly affects computers built before about 1999, and, in fact, for modern computers no emulation mode is generally the more reliable method.
PXELINUX is used in conjunction with a PXE compliant ROM on a network card. The PXE environment uses DHCP or BOOTP to enable basic TCP/IP networking, then downloads a bootstrap program via TFTP. This bootstrap program loads and configures a kernel according to directives that are also downloaded from the TFTP server.
Typically, PXELINUX is used for Linux installations from a central network server or for booting diskless workstations.
EXTLINUX is typically used as a general-purpose bootloader, similar to LILO or GRUB.
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