3 A suite of bootloaders for Linux
5 Copyright (C) 1994-2004 H. Peter Anvin
7 This program is provided under the terms of the GNU General Public
8 License, version 2 or, at your option, any later version. There is no
9 warranty, neither expressed nor implied, to the function of this
10 program. Please see the included file COPYING for details.
12 ----------------------------------------------------------------------
14 SYSLINUX now has a home page at http://syslinux.zytor.com/
16 ----------------------------------------------------------------------
18 The SYSLINUX suite contains the following boot loaders
19 ("derivatives"), for their respective boot media:
21 SYSLINUX - MS-DOS/Windows FAT filesystem
22 PXELINUX - PXE network booting
23 ISOLINUX - ISO9660 CD-ROM
24 EXTLINUX - Linux ext2/ext3 filesystem
26 For historical reasons, some of the sections in this document applies
27 to the FAT loader only; see pxelinux.doc, isolinux.doc and
28 extlinux.doc for what differs in these versions.
30 Help with cleaning up the docs would be greatly appreciated.
33 ++++ CREATING A BOOTABLE LINUX FLOPPY +++
35 In order to create a bootable Linux floppy using SYSLINUX, prepare a
36 normal MS-DOS formatted floppy. Copy one or more Linux kernel files to
37 it, then execute the DOS command:
41 (or whichever drive letter is appropriate; the [] meaning -s is optional)
43 Use "syslinux.com" (in the dos subdirectory of the distribution) for
44 plain DOS (MS-DOS, DR-DOS, PC-DOS, FreeDOS...) or Win9x/ME.
46 Use "syslinux.exe" (in the win32 subdirectory of the distribution) for
49 Under Linux, execute the command:
51 syslinux [-s] [-o offset] /dev/fd0
53 (or, again, whichever device is the correct one.)
55 This will alter the boot sector on the disk and copy a file named
56 LDLINUX.SYS into its root directory.
58 The -s option, if given, will install a "safe, slow and stupid"
59 version of SYSLINUX. This version may work on some very buggy BIOSes
60 on which SYSLINUX would otherwise fail. If you find a machine on
61 which the -s option is required to make it boot reliably, please send
62 as much info about your machine as you can, and include the failure
65 The -o option is used with a disk image file and specifies the byte
66 offset of the filesystem image in the file.
68 On boot time, by default, the kernel will be loaded from the image named
69 LINUX on the boot floppy. This default can be changed, see the section
70 on the SYSLINUX config file.
72 If the Shift or Alt keys are held down during boot, or the Caps or Scroll
73 locks are set, SYSLINUX will display a LILO-style "boot:" prompt. The
74 user can then type a kernel file name followed by any kernel parameters.
75 The SYSLINUX loader does not need to know about the kernel file in
76 advance; all that is required is that it is a file located in the root
77 directory on the disk.
79 There are two versions of the Linux installer; one in the "mtools"
80 directory which requires no special privilege (other than write
81 permission to the device where you are installing) but requires the
82 mtools program suite to be available, and one in the "unix" directory
83 which requires root privilege.
86 ++++ CONFIGURATION FILE ++++
88 All the configurable defaults in SYSLINUX can be changed by putting a
89 file called SYSLINUX.CFG in the root directory of the boot floppy. This
90 is a text file in either UNIX or DOS format, containing one or more of
91 the following items (case is insensitive for keywords; upper case is used
92 here to indicate that a word should be typed verbatim):
94 All options here applies to PXELINUX, ISOLINUX and EXTLINUX as well as
95 SYSLINUX unless otherwise noted. See the respective .doc files.
98 A comment line. The whitespace after the hash mark is mandatory.
100 DEFAULT kernel options...
101 Sets the default command line. If SYSLINUX boots automatically,
102 it will act just as if the entries after DEFAULT had been typed
103 in at the "boot:" prompt.
105 If no configuration file is present, or no DEFAULT entry is
106 present in the config file, the default is "linux auto".
108 NOTE: Earlier versions of SYSLINUX used to automatically
109 append the string "auto" to whatever the user specified using
110 the DEFAULT command. As of version 1.54, this is no longer
111 true, as it caused problems when using a shell as a substitute
112 for "init." You may want to include this option manually.
115 Add one or more options to the kernel command line. These are
116 added both for automatic and manual boots. The options are
117 added at the very beginning of the kernel command line,
118 usually permitting explicitly entered kernel options to override
119 them. This is the equivalent of the LILO "append" option.
121 IPAPPEND flag_val [PXELINUX only]
122 The IPAPPEND option is available only on PXELINUX. The
123 flag_val is an OR of the following options:
125 1: indicates that an option of the following format
126 should be generated and added to the kernel command line:
128 ip=<client-ip>:<boot-server-ip>:<gw-ip>:<netmask>
130 ... based on the input from the DHCP/BOOTP or PXE boot server.
132 THE USE OF THIS OPTION IS NOT RECOMMENDED. If you have to use
133 it, it is probably an indication that your network configuration
134 is broken. Using just "ip=dhcp" on the kernel command line
135 is a preferrable option, or, better yet, run dhcpcd/dhclient,
136 from an initrd if necessary.
138 2: indicates that an option of the following format
139 should be generated and added to the kernel command line:
141 BOOTIF=<hardware-address-of-boot-interface>
143 ... in dash-separated hexadecimal with leading hardware type
144 (same as for the configuration file; see pxelinux.doc.)
146 This allows an initrd program to determine from which
147 interface the system booted.
152 IPAPPEND flag_val [PXELINUX only]
153 Indicates that if "label" is entered as the kernel to boot,
154 SYSLINUX should instead boot "image", and the specified APPEND
155 and IPAPPEND options should be used instead of the ones
156 specified in the global section of the file (before the first
157 LABEL command.) The default for "image" is the same as
158 "label", and if no APPEND is given the default is to use the
159 global entry (if any).
161 Starting with version 2.20, LABEL statements are compressed
162 internally, therefore the maximum number of LABEL statements
163 depends on their complexity. Typical is around 600. SYSLINUX
164 will print an error message if the internal memory for labels
167 Note that LILO uses the syntax:
172 ... whereas SYSLINUX uses the syntax:
177 Notes: Labels are mangled as if they were filenames, and must be
178 unique after mangling. For example, two labels
179 "v2.1.30" and "v2.1.31" will not be distinguishable
180 under SYSLINUX, since both mangle to the same DOS filename.
182 The "kernel" doesn't have to be a Linux kernel; it can
183 be a boot sector or a COMBOOT file (see below.)
186 Append nothing. APPEND with a single hyphen as argument in a
187 LABEL section can be used to override a global APPEND.
189 LOCALBOOT type [ISOLINUX, PXELINUX]
190 On PXELINUX, specifying "LOCALBOOT 0" instead of a "KERNEL"
191 option means invoking this particular label will cause a local
192 disk boot instead of booting a kernel.
194 The argument 0 means perform a normal boot. The argument 4
195 will perform a local boot with the Universal Network Driver
196 Interface (UNDI) driver still resident in memory. Finally,
197 the argument 5 will perform a local boot with the entire PXE
198 stack, including the UNDI driver, still resident in memory.
199 All other values are undefined. If you don't know what the
200 UNDI or PXE stacks are, don't worry -- you don't want them,
203 On ISOLINUX, the "type" specifies the local drive number to
204 boot from; 0x00 is the primary floppy drive and 0x80 is the
205 primary hard drive. The special value -1 causes ISOLINUX to
206 report failure to the BIOS, which, on recent BIOSes, should
207 mean that the next boot device in the boot sequence should be
211 If flag_val is 0, do not load a kernel image unless it has been
212 explicitly named in a LABEL statement. The default is 1.
214 ALLOWOPTIONS flag_val
215 If flag_val is 0, the user is not allowed to specify any
216 arguments on the kernel command line. The only options
217 recognized are those specified in an APPEND statement. The
221 Indicates how long to wait at the boot: prompt until booting
222 automatically, in units of 1/10 s. The timeout is cancelled as
223 soon as the user types anything on the keyboard, the assumption
224 being that the user will complete the command line already
225 begun. A timeout of zero will disable the timeout completely,
226 this is also the default.
228 NOTE: The maximum possible timeout value is 35996; corresponding to
231 ONTIMEOUT kernel options...
232 Sets the command line invoked on a timeout. Normally this is
233 the same thing as invoked by "DEFAULT". If this is specified,
234 then "DEFAULT" is used only if the user presses <Enter> to
237 ONERROR kernel options...
238 If a kernel image is not found (either due to it not existing,
239 or because IMPLICIT is set), run the specified command. The
240 faulty command line is appended to the specified options, so
241 if the ONERROR directive reads as:
245 ... and the command line as entered by the user is:
249 ... SYSLINUX will execute the following as if entered by the
252 xyzzy plugh foo bar baz
254 SERIAL port [[baudrate] flowcontrol]
255 Enables a serial port to act as the console. "port" is a
256 number (0 = /dev/ttyS0 = COM1, etc.) or an I/O port address
257 (e.g. 0x3F8); if "baudrate" is omitted, the baud rate defaults
258 to 9600 bps. The serial parameters are hardcoded to be 8
259 bits, no parity, 1 stop bit.
261 "flowcontrol" is a combination of the following bits:
264 0x010 - Wait for CTS assertion
265 0x020 - Wait for DSR assertion
266 0x040 - Wait for RI assertion
267 0x080 - Wait for DCD assertion
268 0x100 - Ignore input unless CTS asserted
269 0x200 - Ignore input unless DSR asserted
270 0x400 - Ignore input unless RI asserted
271 0x800 - Ignore input unless DCD asserted
273 All other bits are reserved.
277 0 - No flow control (default)
278 0x303 - Null modem cable detect
279 0x013 - RTS/CTS flow control
280 0x813 - RTS/CTS flow control, modem input
281 0x023 - DTR/DSR flow control
282 0x083 - DTR/DCD flow control
284 For the SERIAL directive to be guaranteed to work properly, it
285 should be the first directive in the configuration file.
287 NOTE: "port" values from 0 to 3 means the first four serial
288 ports detected by the BIOS. They may or may not correspond to
289 the legacy port values 0x3F8, 0x2F8, 0x3E8, 0x2E8.
292 If flag_val is 0, disable output to the normal video console.
293 If flag_val is 1, enable output to the video console (this is
296 Some BIOSes try to forward this to the serial console and
297 sometimes make a total mess thereof, so this option lets you
298 disable the video console on these systems.
301 Load a font in .psf format before displaying any output
302 (except the copyright line, which is output as ldlinux.sys
303 itself is loaded.) SYSLINUX only loads the font onto the
304 video card; if the .psf file contains a Unicode table it is
305 ignored. This only works on EGA and VGA cards; hopefully it
306 should do nothing on others.
309 Install a simple keyboard map. The keyboard remapper used is
310 *very* simplistic (it simply remaps the keycodes received from
311 the BIOS, which means that only the key combinations relevant
312 in the default layout -- usually U.S. English -- can be
313 mapped) but should at least help people with AZERTY keyboard
314 layout and the locations of = and , (two special characters
315 used heavily on the Linux kernel command line.)
317 The included program keytab-lilo.pl from the LILO distribution
318 can be used to create such keymaps. The file keytab-lilo.doc
319 contains the documentation for this program.
322 Displays the indicated file on the screen at boot time (before
323 the boot: prompt, if displayed). Please see the section below
326 NOTE: If the file is missing, this option is simply ignored.
329 Prints the message on the screen.
332 If flag_val is 0, display the boot: prompt only if the Shift or Alt
333 key is pressed, or Caps Lock or Scroll lock is set (this is the
334 default). If flag_val is 1, always display the boot: prompt.
337 If flag_val is set to 1, ignore the Shift/Alt/Caps Lock/Scroll
338 Lock escapes. Use this (together with PROMPT 0) to force the
339 default boot alternative.
346 Displays the indicated file on the screen when a function key is
347 pressed at the boot: prompt. This can be used to implement
348 pre-boot online help (presumably for the kernel command line
349 options.) Note that F10 MUST be entered in the config file as
350 "F0", not "F10", and that there is currently no way to bind
351 file names to F11 and F12. Please see the section below on
354 When using the serial console, press <Ctrl-F><digit> to get to
355 the help screens, e.g. <Ctrl-F><2> to get to the F2 screen,
356 and <Ctrl-F><0> for the F10 one.
358 Blank lines are ignored.
360 Note that the configuration file is not completely decoded. Syntax
361 different from the one described above may still work correctly in this
362 version of SYSLINUX, but may break in a future one.
365 ++++ DISPLAY FILE FORMAT ++++
367 DISPLAY and function-key help files are text files in either DOS or UNIX
368 format (with or without <CR>). In addition, the following special codes
371 <FF> <FF> = <Ctrl-L> = ASCII 12
372 Clear the screen, home the cursor. Note that the screen is
373 filled with the current display color.
375 <SI><bg><fg> <SI> = <Ctrl-O> = ASCII 15
376 Set the display colors to the specified background and
377 foreground colors, where <bg> and <fg> are hex digits,
378 corresponding to the standard PC display attributes:
380 0 = black 8 = dark grey
381 1 = dark blue 9 = bright blue
382 2 = dark green a = bright green
383 3 = dark cyan b = bright cyan
384 4 = dark red c = bright red
385 5 = dark purple d = bright purple
387 7 = light grey f = white
389 Picking a bright color (8-f) for the background results in the
390 corresponding dark color (0-7), with the foreground flashing.
392 Colors are not visible over the serial console.
394 <CAN>filename<newline> <CAN> = <Ctrl-X> = ASCII 24
395 If a VGA display is present, enter graphics mode and display
396 the graphic included in the specified file. The file format
397 is an ad hoc format called LSS16; the included Perl program
398 "ppmtolss16" can be used to produce these images. This Perl
399 program also includes the file format specification.
401 The image is displayed in 640x480 16-color mode. Once in
402 graphics mode, the display attributes (set by <SI> code
403 sequences) work slightly differently: the background color is
404 ignored, and the foreground colors are the 16 colors specified
405 in the image file. For that reason, ppmtolss16 allows you to
406 specify that certain colors should be assigned to specific
409 Color indicies 0 and 7, in particular, should be chosen with
410 care: 0 is the background color, and 7 is the color used for
411 the text printed by SYSLINUX itself.
413 <EM> <EM> = <Ctrl-Y> = ASCII 25
414 If we are currently in graphics mode, return to text mode.
416 <DLE>..<ETB> <Ctrl-P>..<Ctrl-W> = ASCII 16-23
417 These codes can be used to select which modes to print a
418 certain part of the message file in. Each of these control
419 characters select a specific set of modes (text screen,
420 graphics screen, serial port) for which the output is actually
423 Character Text Graph Serial
424 ------------------------------------------------------
425 <DLE> = <Ctrl-P> = ASCII 16 No No No
426 <DC1> = <Ctrl-Q> = ASCII 17 Yes No No
427 <DC2> = <Ctrl-R> = ASCII 18 No Yes No
428 <DC3> = <Ctrl-S> = ASCII 19 Yes Yes No
429 <DC4> = <Ctrl-T> = ASCII 20 No No Yes
430 <NAK> = <Ctrl-U> = ASCII 21 Yes No Yes
431 <SYN> = <Ctrl-V> = ASCII 22 No Yes Yes
432 <ETB> = <Ctrl-W> = ASCII 23 Yes Yes Yes
436 <DC1>Text mode<DC2>Graphics mode<DC4>Serial port<ETB>
438 ... will actually print out which mode the console is in!
440 <SUB> <SUB> = <Ctrl-Z> = ASCII 26
441 End of file (DOS convention).
444 ++++ COMMAND LINE KEYSTROKES ++++
446 The command line prompt supports the following keystrokes:
448 <Enter> boot specified command line
449 <BackSpace> erase one character
450 <Ctrl-U> erase the whole line
451 <Ctrl-V> display the current SYSLINUX version
452 <Ctrl-W> erase one word
453 <Ctrl-X> force text mode
454 <F1>..<F10> help screens (if configured)
455 <Ctrl-F><digit> equivalent to F1..F10
456 <Ctrl-C> interrupt boot in progress
457 <Esc> interrupt boot in progress
460 ++++ COMBOOT IMAGES AND OTHER OPERATING SYSTEMS ++++
462 This version of SYSLINUX supports chain loading of other operating
463 systems (such as MS-DOS and its derivatives, including Windows 95/98),
464 as well as COMBOOT-style standalone executables (a subset of DOS .COM
465 files; see separate section below.)
467 Chain loading requires the boot sector of the foreign operating system
468 to be stored in a file in the root directory of the filesystem.
469 Because neither Linux kernels, boot sector images, nor COMBOOT files
470 have reliable magic numbers, SYSLINUX will look at the file extension.
471 The following extensions are recognized (case insensitive):
473 none or other Linux kernel image
474 .0 PXE bootstrap program (NBP) [PXELINUX only]
475 .bin "CD boot sector" [ISOLINUX only]
476 .bs Boot sector [SYSLINUX only]
477 .bss Boot sector, DOS superblock will be patched in [SYSLINUX only]
478 .c32 COM32 image (32-bit COMBOOT)
479 .cbt COMBOOT image (not runnable from DOS)
480 .com COMBOOT image (runnable from DOS)
481 .img Disk image [ISOLINUX only]
483 For filenames given on the command line, SYSLINUX will search for the
484 file by adding extensions in the order listed above if the plain
485 filename is not found. Filenames in KERNEL statements must be fully
489 ++++ BOOTING DOS (OR OTHER SIMILAR OPERATING SYSTEMS) ++++
491 This section applies to SYSLINUX only, not to PXELINUX or ISOLINUX.
492 See isolinux.doc for an equivalent procedure for ISOLINUX.
494 This is the recommended procedure for creating a SYSLINUX disk that
495 can boot either DOS or Linux. This example assumes the drive is A: in
496 DOS and /dev/fd0 in Linux; for other drives, substitute the
497 appropriate drive designator.
499 ---- Linux procedure ----
501 1. Make a DOS bootable disk. This can be done either by specifying
502 the /s option when formatting the disk in DOS, or by running the
503 DOS command SYS (this can be done under DOSEMU if DOSEMU has
504 direct device access to the relevant drive):
510 2. Boot Linux. Copy the DOS boot sector from the disk into a file:
512 dd if=/dev/fd0 of=dos.bss bs=512 count=1
514 3. Run SYSLINUX on the disk:
518 4. Mount the disk and copy the DOS boot sector file to it. The file
519 *must* have extension .bss:
521 mount -t msdos /dev/fd0 /mnt
524 5. Copy the Linux kernel image(s), initrd(s), etc to the disk, and
525 create/edit syslinux.cfg and help files if desired:
530 6. Unmount the disk (if applicable.)
534 ---- DOS/Windows procedure ----
536 To make this installation in DOS only, you need the utility copybs.com
537 (included with SYSLINUX) as well as the syslinux.com installer. If
538 you are on an WinNT-based system (WinNT, Win2k, WinXP or later), use
539 syslinux.exe instead.
541 1. Make a DOS bootable disk. This can be done either by specifying
542 the /s option when formatting the disk in DOS, or by running the
549 2. Copy the DOS boot sector from the disk into a file. The file
550 *must* have extension .bss:
554 3. Run SYSLINUX on the disk:
558 4. Copy the Linux kernel image(s), initrd(s), etc to the disk, and
559 create/edit syslinux.cfg and help files if desired:
565 ++++ COMBOOT EXECUTABLES ++++
567 SYSLINUX supports simple standalone programs, using a file format
568 similar to DOS ".com" files. A 32-bit version, called COM32, is also
569 provided. A simple API provides access to a limited set of filesystem
570 and console functions.
572 See the file comboot.doc for more information on COMBOOT and COM32
576 ++++ NOVICE PROTECTION ++++
578 SYSLINUX will attempt to detect booting on a machine with too little
579 memory, which means the Linux boot sequence cannot complete. If so, a
580 message is displayed and the boot sequence aborted. Holding down the
581 Ctrl key while booting disables this feature.
583 Any file that SYSLINUX uses can be marked hidden, system or readonly
584 if so is convenient; SYSLINUX ignores all file attributes. The
585 SYSLINUX installed automatically sets the readonly/hidden/system
586 attributes on LDLINUX.SYS.
589 ++++ NOTES ON BOOTABLE CD-ROMS ++++
591 SYSLINUX can be used to create bootdisk images for El
592 Torito-compatible bootable CD-ROMs. However, it appears that many
593 BIOSes are very buggy when it comes to booting CD-ROMs. Some users
594 have reported that the following steps are helpful in making a CD-ROM
595 that is bootable on the largest possible number of machines:
597 a) Use the -s (safe, slow and stupid) option to SYSLINUX;
598 b) Put the boot image as close to the beginning of the
599 ISO 9660 filesystem as possible.
601 A CD-ROM is so much faster than a floppy that the -s option shouldn't
602 matter from a speed perspective.
604 Of course, you probably want to use ISOLINUX instead. See isolinux.doc.
607 ++++ BOOTING FROM A FAT FILESYSTEM PARTITION ON A HARD DISK ++++
609 SYSLINUX can boot from a FAT filesystem partition on a hard disk
610 (including FAT32). The installation procedure is identical to the
611 procedure for installing it on a floppy, and should work under either
612 DOS or Linux. To boot from a partition, SYSLINUX needs to be launched
613 from a Master Boot Record or another boot loader, just like DOS itself
616 Under DOS, you can install a standard simple MBR on the primary hard
617 disk by running the command:
621 Then use the FDISK command to mark the appropriate partition active.
623 A simple MBR, roughly on par with the one installed by DOS (but
624 unencumbered), is included in the SYSLINUX distribution. To install
625 it under Linux, simply type:
627 cat mbr.bin > /dev/XXX
629 ... where /dev/XXX is the device you wish to install it on.
631 Under DOS or Win32, you can install the SYSLINUX MBR with the -m
632 option to the SYSLINUX installer, and use the -a option to mark the
633 current partition active:
637 Note that this will also install SYSLINUX on the specified partition.
640 ++++ HARDWARE INFORMATION +++
642 I have started to maintain a web page of hardware with known
643 problems. There are, unfortunately, lots of broken hardware out
644 there; especially early PXE stacks (for PXELINUX) have lots of
647 A list of problems, and workarounds (if known), is maintained at:
649 http://syslinux.zytor.com/hardware.php
652 ++++ BOOT LOADER IDS USED ++++
654 The Linux boot protocol supports a "boot loader ID", a single byte
655 where the upper nybble specifies a boot loader family (3 = SYSLINUX)
656 and the lower nybble is version or, in the case of SYSLINUX, media:
664 ++++ BUG REPORTS ++++
666 I would appreciate hearing of any problems you have with SYSLINUX. I
667 would also like to hear from you if you have successfully used SYSLINUX,
668 *especially* if you are using it for a distribution.
670 If you are reporting problems, please include all possible information
671 about your system and your BIOS; the vast majority of all problems
672 reported turn out to be BIOS or hardware bugs, and I need as much
673 information as possible in order to diagnose the problems.
675 There is a mailing list for discussion among SYSLINUX users and for
676 announcements of new and test versions. To join, or to browse the
679 http://www.zytor.com/mailman/listinfo/syslinux
681 Please DO NOT send HTML messages or attachments to the mailing list
682 (including multipart/alternative or similar.) All such messages will