3 A suite of bootloaders for Linux
5 Copyright (C) 1994-2005 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.
181 This is also true for "foo bar" and "foo baz".
183 The "kernel" doesn't have to be a Linux kernel; it can
184 be a boot sector or a COMBOOT file (see below.)
187 Append nothing. APPEND with a single hyphen as argument in a
188 LABEL section can be used to override a global APPEND.
190 LOCALBOOT type [ISOLINUX, PXELINUX]
191 On PXELINUX, specifying "LOCALBOOT 0" instead of a "KERNEL"
192 option means invoking this particular label will cause a local
193 disk boot instead of booting a kernel.
195 The argument 0 means perform a normal boot. The argument 4
196 will perform a local boot with the Universal Network Driver
197 Interface (UNDI) driver still resident in memory. Finally,
198 the argument 5 will perform a local boot with the entire PXE
199 stack, including the UNDI driver, still resident in memory.
200 All other values are undefined. If you don't know what the
201 UNDI or PXE stacks are, don't worry -- you don't want them,
204 On ISOLINUX, the "type" specifies the local drive number to
205 boot from; 0x00 is the primary floppy drive and 0x80 is the
206 primary hard drive. The special value -1 causes ISOLINUX to
207 report failure to the BIOS, which, on recent BIOSes, should
208 mean that the next boot device in the boot sequence should be
212 If flag_val is 0, do not load a kernel image unless it has been
213 explicitly named in a LABEL statement. The default is 1.
215 ALLOWOPTIONS flag_val
216 If flag_val is 0, the user is not allowed to specify any
217 arguments on the kernel command line. The only options
218 recognized are those specified in an APPEND statement. The
222 Indicates how long to wait at the boot: prompt until booting
223 automatically, in units of 1/10 s. The timeout is cancelled as
224 soon as the user types anything on the keyboard, the assumption
225 being that the user will complete the command line already
226 begun. A timeout of zero will disable the timeout completely,
227 this is also the default.
229 NOTE: The maximum possible timeout value is 35996; corresponding to
232 ONTIMEOUT kernel options...
233 Sets the command line invoked on a timeout. Normally this is
234 the same thing as invoked by "DEFAULT". If this is specified,
235 then "DEFAULT" is used only if the user presses <Enter> to
238 ONERROR kernel options...
239 If a kernel image is not found (either due to it not existing,
240 or because IMPLICIT is set), run the specified command. The
241 faulty command line is appended to the specified options, so
242 if the ONERROR directive reads as:
246 ... and the command line as entered by the user is:
250 ... SYSLINUX will execute the following as if entered by the
253 xyzzy plugh foo bar baz
255 SERIAL port [[baudrate] flowcontrol]
256 Enables a serial port to act as the console. "port" is a
257 number (0 = /dev/ttyS0 = COM1, etc.) or an I/O port address
258 (e.g. 0x3F8); if "baudrate" is omitted, the baud rate defaults
259 to 9600 bps. The serial parameters are hardcoded to be 8
260 bits, no parity, 1 stop bit.
262 "flowcontrol" is a combination of the following bits:
265 0x010 - Wait for CTS assertion
266 0x020 - Wait for DSR assertion
267 0x040 - Wait for RI assertion
268 0x080 - Wait for DCD assertion
269 0x100 - Ignore input unless CTS asserted
270 0x200 - Ignore input unless DSR asserted
271 0x400 - Ignore input unless RI asserted
272 0x800 - Ignore input unless DCD asserted
274 All other bits are reserved.
278 0 - No flow control (default)
279 0x303 - Null modem cable detect
280 0x013 - RTS/CTS flow control
281 0x813 - RTS/CTS flow control, modem input
282 0x023 - DTR/DSR flow control
283 0x083 - DTR/DCD flow control
285 For the SERIAL directive to be guaranteed to work properly, it
286 should be the first directive in the configuration file.
288 NOTE: "port" values from 0 to 3 means the first four serial
289 ports detected by the BIOS. They may or may not correspond to
290 the legacy port values 0x3F8, 0x2F8, 0x3E8, 0x2E8.
293 If flag_val is 0, disable output to the normal video console.
294 If flag_val is 1, enable output to the video console (this is
297 Some BIOSes try to forward this to the serial console and
298 sometimes make a total mess thereof, so this option lets you
299 disable the video console on these systems.
302 Load a font in .psf format before displaying any output
303 (except the copyright line, which is output as ldlinux.sys
304 itself is loaded.) SYSLINUX only loads the font onto the
305 video card; if the .psf file contains a Unicode table it is
306 ignored. This only works on EGA and VGA cards; hopefully it
307 should do nothing on others.
310 Install a simple keyboard map. The keyboard remapper used is
311 *very* simplistic (it simply remaps the keycodes received from
312 the BIOS, which means that only the key combinations relevant
313 in the default layout -- usually U.S. English -- can be
314 mapped) but should at least help people with AZERTY keyboard
315 layout and the locations of = and , (two special characters
316 used heavily on the Linux kernel command line.)
318 The included program keytab-lilo.pl from the LILO distribution
319 can be used to create such keymaps. The file keytab-lilo.doc
320 contains the documentation for this program.
323 Displays the indicated file on the screen at boot time (before
324 the boot: prompt, if displayed). Please see the section below
327 NOTE: If the file is missing, this option is simply ignored.
330 Prints the message on the screen.
333 If flag_val is 0, display the boot: prompt only if the Shift or Alt
334 key is pressed, or Caps Lock or Scroll lock is set (this is the
335 default). If flag_val is 1, always display the boot: prompt.
338 If flag_val is set to 1, ignore the Shift/Alt/Caps Lock/Scroll
339 Lock escapes. Use this (together with PROMPT 0) to force the
340 default boot alternative.
347 Displays the indicated file on the screen when a function key is
348 pressed at the boot: prompt. This can be used to implement
349 pre-boot online help (presumably for the kernel command line
350 options.) Note that F10 MUST be entered in the config file as
351 "F0", not "F10", and that there is currently no way to bind
352 file names to F11 and F12. Please see the section below on
355 When using the serial console, press <Ctrl-F><digit> to get to
356 the help screens, e.g. <Ctrl-F><2> to get to the F2 screen,
357 and <Ctrl-F><0> for the F10 one.
359 Blank lines are ignored.
361 Note that the configuration file is not completely decoded. Syntax
362 different from the one described above may still work correctly in this
363 version of SYSLINUX, but may break in a future one.
366 ++++ DISPLAY FILE FORMAT ++++
368 DISPLAY and function-key help files are text files in either DOS or UNIX
369 format (with or without <CR>). In addition, the following special codes
372 <FF> <FF> = <Ctrl-L> = ASCII 12
373 Clear the screen, home the cursor. Note that the screen is
374 filled with the current display color.
376 <SI><bg><fg> <SI> = <Ctrl-O> = ASCII 15
377 Set the display colors to the specified background and
378 foreground colors, where <bg> and <fg> are hex digits,
379 corresponding to the standard PC display attributes:
381 0 = black 8 = dark grey
382 1 = dark blue 9 = bright blue
383 2 = dark green a = bright green
384 3 = dark cyan b = bright cyan
385 4 = dark red c = bright red
386 5 = dark purple d = bright purple
388 7 = light grey f = white
390 Picking a bright color (8-f) for the background results in the
391 corresponding dark color (0-7), with the foreground flashing.
393 Colors are not visible over the serial console.
395 <CAN>filename<newline> <CAN> = <Ctrl-X> = ASCII 24
396 If a VGA display is present, enter graphics mode and display
397 the graphic included in the specified file. The file format
398 is an ad hoc format called LSS16; the included Perl program
399 "ppmtolss16" can be used to produce these images. This Perl
400 program also includes the file format specification.
402 The image is displayed in 640x480 16-color mode. Once in
403 graphics mode, the display attributes (set by <SI> code
404 sequences) work slightly differently: the background color is
405 ignored, and the foreground colors are the 16 colors specified
406 in the image file. For that reason, ppmtolss16 allows you to
407 specify that certain colors should be assigned to specific
410 Color indicies 0 and 7, in particular, should be chosen with
411 care: 0 is the background color, and 7 is the color used for
412 the text printed by SYSLINUX itself.
414 <EM> <EM> = <Ctrl-Y> = ASCII 25
415 If we are currently in graphics mode, return to text mode.
417 <DLE>..<ETB> <Ctrl-P>..<Ctrl-W> = ASCII 16-23
418 These codes can be used to select which modes to print a
419 certain part of the message file in. Each of these control
420 characters select a specific set of modes (text screen,
421 graphics screen, serial port) for which the output is actually
424 Character Text Graph Serial
425 ------------------------------------------------------
426 <DLE> = <Ctrl-P> = ASCII 16 No No No
427 <DC1> = <Ctrl-Q> = ASCII 17 Yes No No
428 <DC2> = <Ctrl-R> = ASCII 18 No Yes No
429 <DC3> = <Ctrl-S> = ASCII 19 Yes Yes No
430 <DC4> = <Ctrl-T> = ASCII 20 No No Yes
431 <NAK> = <Ctrl-U> = ASCII 21 Yes No Yes
432 <SYN> = <Ctrl-V> = ASCII 22 No Yes Yes
433 <ETB> = <Ctrl-W> = ASCII 23 Yes Yes Yes
437 <DC1>Text mode<DC2>Graphics mode<DC4>Serial port<ETB>
439 ... will actually print out which mode the console is in!
441 <SUB> <SUB> = <Ctrl-Z> = ASCII 26
442 End of file (DOS convention).
444 <BEL> <BEL> = <Ctrl-G> = ASCII 7
448 ++++ COMMAND LINE KEYSTROKES ++++
450 The command line prompt supports the following keystrokes:
452 <Enter> boot specified command line
453 <BackSpace> erase one character
454 <Ctrl-U> erase the whole line
455 <Ctrl-V> display the current SYSLINUX version
456 <Ctrl-W> erase one word
457 <Ctrl-X> force text mode
458 <F1>..<F10> help screens (if configured)
459 <Ctrl-F><digit> equivalent to F1..F10
460 <Ctrl-C> interrupt boot in progress
461 <Esc> interrupt boot in progress
464 ++++ COMBOOT IMAGES AND OTHER OPERATING SYSTEMS ++++
466 This version of SYSLINUX supports chain loading of other operating
467 systems (such as MS-DOS and its derivatives, including Windows 95/98),
468 as well as COMBOOT-style standalone executables (a subset of DOS .COM
469 files; see separate section below.)
471 Chain loading requires the boot sector of the foreign operating system
472 to be stored in a file in the root directory of the filesystem.
473 Because neither Linux kernels, boot sector images, nor COMBOOT files
474 have reliable magic numbers, SYSLINUX will look at the file extension.
475 The following extensions are recognized (case insensitive):
477 none or other Linux kernel image
478 .0 PXE bootstrap program (NBP) [PXELINUX only]
479 .bin "CD boot sector" [ISOLINUX only]
480 .bs Boot sector [SYSLINUX only]
481 .bss Boot sector, DOS superblock will be patched in [SYSLINUX only]
482 .c32 COM32 image (32-bit COMBOOT)
483 .cbt COMBOOT image (not runnable from DOS)
484 .com COMBOOT image (runnable from DOS)
485 .img Disk image [ISOLINUX only]
487 For filenames given on the command line, SYSLINUX will search for the
488 file by adding extensions in the order listed above if the plain
489 filename is not found. Filenames in KERNEL statements must be fully
493 ++++ BOOTING DOS (OR OTHER SIMILAR OPERATING SYSTEMS) ++++
495 This section applies to SYSLINUX only, not to PXELINUX or ISOLINUX.
496 See isolinux.doc for an equivalent procedure for ISOLINUX.
498 This is the recommended procedure for creating a SYSLINUX disk that
499 can boot either DOS or Linux. This example assumes the drive is A: in
500 DOS and /dev/fd0 in Linux; for other drives, substitute the
501 appropriate drive designator.
503 ---- Linux procedure ----
505 1. Make a DOS bootable disk. This can be done either by specifying
506 the /s option when formatting the disk in DOS, or by running the
507 DOS command SYS (this can be done under DOSEMU if DOSEMU has
508 direct device access to the relevant drive):
514 2. Boot Linux. Copy the DOS boot sector from the disk into a file:
516 dd if=/dev/fd0 of=dos.bss bs=512 count=1
518 3. Run SYSLINUX on the disk:
522 4. Mount the disk and copy the DOS boot sector file to it. The file
523 *must* have extension .bss:
525 mount -t msdos /dev/fd0 /mnt
528 5. Copy the Linux kernel image(s), initrd(s), etc to the disk, and
529 create/edit syslinux.cfg and help files if desired:
534 6. Unmount the disk (if applicable.)
538 ---- DOS/Windows procedure ----
540 To make this installation in DOS only, you need the utility copybs.com
541 (included with SYSLINUX) as well as the syslinux.com installer. If
542 you are on an WinNT-based system (WinNT, Win2k, WinXP or later), use
543 syslinux.exe instead.
545 1. Make a DOS bootable disk. This can be done either by specifying
546 the /s option when formatting the disk in DOS, or by running the
553 2. Copy the DOS boot sector from the disk into a file. The file
554 *must* have extension .bss:
558 3. Run SYSLINUX on the disk:
562 4. Copy the Linux kernel image(s), initrd(s), etc to the disk, and
563 create/edit syslinux.cfg and help files if desired:
569 ++++ COMBOOT EXECUTABLES ++++
571 SYSLINUX supports simple standalone programs, using a file format
572 similar to DOS ".com" files. A 32-bit version, called COM32, is also
573 provided. A simple API provides access to a limited set of filesystem
574 and console functions.
576 See the file comboot.doc for more information on COMBOOT and COM32
580 ++++ NOVICE PROTECTION ++++
582 SYSLINUX will attempt to detect booting on a machine with too little
583 memory, which means the Linux boot sequence cannot complete. If so, a
584 message is displayed and the boot sequence aborted. Holding down the
585 Ctrl key while booting disables this feature.
587 Any file that SYSLINUX uses can be marked hidden, system or readonly
588 if so is convenient; SYSLINUX ignores all file attributes. The
589 SYSLINUX installed automatically sets the readonly/hidden/system
590 attributes on LDLINUX.SYS.
593 ++++ NOTES ON BOOTABLE CD-ROMS ++++
595 SYSLINUX can be used to create bootdisk images for El
596 Torito-compatible bootable CD-ROMs. However, it appears that many
597 BIOSes are very buggy when it comes to booting CD-ROMs. Some users
598 have reported that the following steps are helpful in making a CD-ROM
599 that is bootable on the largest possible number of machines:
601 a) Use the -s (safe, slow and stupid) option to SYSLINUX;
602 b) Put the boot image as close to the beginning of the
603 ISO 9660 filesystem as possible.
605 A CD-ROM is so much faster than a floppy that the -s option shouldn't
606 matter from a speed perspective.
608 Of course, you probably want to use ISOLINUX instead. See isolinux.doc.
611 ++++ BOOTING FROM A FAT FILESYSTEM PARTITION ON A HARD DISK ++++
613 SYSLINUX can boot from a FAT filesystem partition on a hard disk
614 (including FAT32). The installation procedure is identical to the
615 procedure for installing it on a floppy, and should work under either
616 DOS or Linux. To boot from a partition, SYSLINUX needs to be launched
617 from a Master Boot Record or another boot loader, just like DOS itself
620 Under DOS, you can install a standard simple MBR on the primary hard
621 disk by running the command:
625 Then use the FDISK command to mark the appropriate partition active.
627 A simple MBR, roughly on par with the one installed by DOS (but
628 unencumbered), is included in the SYSLINUX distribution. To install
629 it under Linux, simply type:
631 cat mbr.bin > /dev/XXX
633 ... where /dev/XXX is the device you wish to install it on.
635 Under DOS or Win32, you can install the SYSLINUX MBR with the -m
636 option to the SYSLINUX installer, and use the -a option to mark the
637 current partition active:
641 Note that this will also install SYSLINUX on the specified partition.
644 ++++ HARDWARE INFORMATION +++
646 I have started to maintain a web page of hardware with known
647 problems. There are, unfortunately, lots of broken hardware out
648 there; especially early PXE stacks (for PXELINUX) have lots of
651 A list of problems, and workarounds (if known), is maintained at:
653 http://syslinux.zytor.com/hardware.php
656 ++++ BOOT LOADER IDS USED ++++
658 The Linux boot protocol supports a "boot loader ID", a single byte
659 where the upper nybble specifies a boot loader family (3 = SYSLINUX)
660 and the lower nybble is version or, in the case of SYSLINUX, media:
668 ++++ BUG REPORTS ++++
670 I would appreciate hearing of any problems you have with SYSLINUX. I
671 would also like to hear from you if you have successfully used SYSLINUX,
672 *especially* if you are using it for a distribution.
674 If you are reporting problems, please include all possible information
675 about your system and your BIOS; the vast majority of all problems
676 reported turn out to be BIOS or hardware bugs, and I need as much
677 information as possible in order to diagnose the problems.
679 There is a mailing list for discussion among SYSLINUX users and for
680 announcements of new and test versions. To join, or to browse the
683 http://www.zytor.com/mailman/listinfo/syslinux
685 Please DO NOT send HTML messages or attachments to the mailing list
686 (including multipart/alternative or similar.) All such messages will