syslinux.cfg(5) Manual Page

A line comment. As of version 3.10, the space between the # and the comment is no longer required.

(3.00+) A directive for the simple menu system, treated as a comment outside the menu. See menu.txt.

Inserts the contents of another file at this point in the configuration file. Files can currently be nested up to 16 levels deep, but it is not guaranteed that more than 8 levels will be supported in the future.

Sets the default command line (which often references a LABEL). If Syslinux boots automatically, it will act just as if the entries after DEFAULT had been typed in at the boot: prompt. Multiple uses will result in an override.

Selects a specific user interface module (typically menu.c32 or vesamenu.c32). The command-line interface treats this as a directive that overrides the DEFAULT directive to load this module instead at startup, for an empty command line and at timeout and PROMPT directive to not prompt (but these directives may have effects on other configuration parsers). Multiple uses will result in an override.

Begin a new LABEL clause. If mylabel is entered as the kernel to boot, Syslinux should instead boot "image" (specified by a directive from KERNEL-LIKE DIRECTIVES) with any specified DUAL-PURPOSE DIRECTIVES being used instead of the global instance.

Add one or more options to the kernel command line. These are added both for automatic and manual boots. The options are added at the very beginning of the kernel command line, usually permitting explicitly entered kernel options to override them. This is the equivalent of the LILO "append" option.

Append nothing. APPEND with a single hyphen as argument in a LABEL section can be used to override a global APPEND.

(SYSAPPEND: 5.10+; IPAPPEND: PXELINUX only) The SYSAPPEND option was introduced in Syslinux 5.10; it is an enhancement of a previous option IPAPPEND which was only available on PXELINUX. bitmask is interpreted as decimal format unless prefixed with "0x" for hexadecimal or "0" (zero) for octal. The bitmask is an OR (sum) of the following integer options:

Load a kernel-like file image with automatic filetype detection based on file extension, listed under the non-auto-detecting directives, defaulting to LINUX.

(ISOLINUX only: .bin; SYSLINUX only: .bs) Load a boot sector. .bin is a "CD boot sector" and .bs is a regular disk boot sector.

(SYSLINUX only: .bss) Load a BSS image, a .bs image with the DOS superblock patched in.

(.com, .cbt; Removed as of 5.00) Load a Syslinux COMBOOT image. .com images may also be runnable from DOS while .cbt images are not. See also comboot.txt

(.c32) Load a Syslinux COM32 (32-bit COMBOOT) image. See also comboot.txt

Load a new configuration file. The configuration file is read, the working directory is changed (if specified via an APPEND), then the configuration file is parsed.

(Removed as of 4.05, added 1.65; ISOLINUX only: .img) Load a disk image.

(PXELINUX 1.53+; ISOLINUX ??3.10+; SYSLINUX 3.70+)Attempt a different local boot method. The special value -1 causes the boot loader to report failure to the BIOS, which, on recent BIOSes, should mean that the next boot device in the boot sequence should be activated. Values other than those documented may produce undesired results.

(PXELINUX only: .0) Load a PXE NBP (Network Boot Program) image. The PXE protocol does not provide any means for specifiying or using a command line or initrd.

(3.71+) An initrd can be specified in a separate statement (INITRD) instead of as part of the APPEND statement; this functionally appends "initrd=initrd_file" to the kernel command line. Like initrd=, this also supports multiple comma separated file names (see APPEND).

If flag_val is 0, the user is not allowed to specify any arguments on the kernel command line. The only options recognized are those specified in an APPEND) statement. The default is 1.

If flag_val is 0, do not load a kernel image unless it has been explicitly named in a LABEL statement. The default is 1.

Indicates how long to wait at the boot: prompt until booting automatically, in units of 1/10 s. The timeout is cancelled as soon as the user types anything on the keyboard, the assumption being that the user will complete the command line already begun. The timer is reset to 0 upon return from an unsuccessful attempt to boot or from a module. A timeout of zero (the default) will disable the timeout completely.

Indicates how long to wait until booting automatically, in units of 1/10 s. This timeout is not cancelled by user input, and can thus be used to deal with serial port glitches or "the user walked away" type situations. A timeout of zero (the default) will disable the timeout completely.

# Wait 5 seconds unless the user types something, but
# always boot after 15 minutes.
TIMEOUT 50
TOTALTIMEOUT 9000

Sets the command line invoked on a timeout (which often references a LABEL). If not specified, UI (if used) or 'DEFAULT is used.

If a kernel image is not found (either due to it not existing, or because IMPLICIT is set), run the specified command. The faulty command line is appended to the specified options, so if the ONERROR directive reads as:

ONERROR xyzzy plugh

foo bar baz

xyzzy plugh foo bar baz

Enables a serial port to act as the console. port is a number (0 = /dev/ttyS0 = COM1, etc.) or an I/O port address (e.g. 0x3F8); if baudrate is omitted, the baud rate defaults to 9600 bps. The serial parameters are hardcoded to be 8 bits, no parity, 1 stop bit.

0x001 - Assert DTR
0x002 - Assert RTS
0x008 - Enable interrupts
0x010 - Wait for CTS assertion
0x020 - Wait for DSR assertion
0x040 - Wait for RI assertion
0x080 - Wait for DCD assertion
0x100 - Ignore input unless CTS asserted
0x200 - Ignore input unless DSR asserted
0x400 - Ignore input unless RI asserted
0x800 - Ignore input unless DCD asserted

    0 - No flow control (default)
0x303 - Null modem cable detect
0x013 - RTS/CTS flow control
0x813 - RTS/CTS flow control, modem input
0x023 - DTR/DSR flow control
0x083 - DTR/DCD flow control

If flag_val is 1, don’t halt the processor while idle. Halting the processor while idle significantly reduces the power consumption, but can cause poor responsiveness to the serial console, especially when using scripts to drive the serial console, as opposed to human interaction.

If flag_val is 0, disable output to the normal video console. If flag_val is 1, enable output to the video console (this is the default.)

Load a font in .psf format before displaying any output (except the copyright line, which is output as ldlinux.sys itself is loaded.) Syslinux only loads the font onto the video card; if the .psf file contains a Unicode table it is ignored. This only works on EGA and VGA cards; hopefully it should do nothing on others.

Install a simple keyboard map. The keyboard remapper used is very simplistic (it simply remaps the keycodes received from the BIOS, which means that only the key combinations relevant in the default layout — usually U.S. English — can be mapped) but should at least help people with AZERTY keyboard layout and the locations of = and , (two special characters used heavily on the Linux kernel command line.)

Displays the indicated file on the screen at boot time (before the boot: prompt, if displayed). Please see the section below on DISPLAY files.

Prints the message on the screen.

If flag_val is 0, display the boot: prompt only if the Shift or Alt key is pressed, or Caps Lock or Scroll lock is set (this is the default). If flag_val is 1, always display the boot: prompt.

If flag_val is set to 1, ignore the Shift/Alt/Caps Lock/Scroll Lock escapes. Use this (together with PROMPT 0) to force the default boot alternative.

If flag_val is set to 1, the Tab key does not display labels at the boot: prompt.

Displays the indicated file on the screen when a function key is pressed at the boot: prompt. This can be used to implement pre-boot online help (presumably for the kernel command line options.) Please see the section below on DISPLAY files.

(5.00+) Specify a space-separated (' ; 5.00-5.10 was a colon ':) list of directories to search when attempting to load modules. This directive is useful for specifying the directories containing the lib*.c32 library files as other modules may be dependent on these files, but may not reside in the same directory. Multiple instances will append additional paths.

(PXELINUX 5.10+) When downloading files over http, the SYSAPPEND strings are prepended with Syslinux and sent to the server as cookies. The cookies are URL-encoded; whitespace is not replaced with underscores.

                                 = <Ctrl-L> = ASCII 12
Clear the screen, home the cursor. Note that the screen is filled with the current display color.

= <Ctrl-L> = ASCII 12; Clear the screen, home the cursor. Note that the screen is filled with the current display color.

<FF> = <Ctrl-L> = ASCII 12

<FF> = <Ctrl-L> = ASCII 12
Clear the screen, home the cursor. Note that the screen is filled with the current display color.

<SI> = <Ctrl-O> = ASCII 15

0 = black               8 = dark grey
1 = dark blue           9 = bright blue
2 = dark green          a = bright green
3 = dark cyan           b = bright cyan
4 = dark red            c = bright red
5 = dark purple         d = bright purple
6 = brown               e = yellow
7 = light grey          f = white

<CAN> = <Ctrl-X> = ASCII 24

<EM> = <Ctrl-Y> = ASCII 25
If we are currently in graphics mode, return to text mode.

<Ctrl-P>..<Ctrl-W> = ASCII 16-23

Character                       Text    Graph   Serial
------------------------------------------------------
<DLE> = <Ctrl-P> = ASCII 16     No      No      No
<DC1> = <Ctrl-Q> = ASCII 17     Yes     No      No
<DC2> = <Ctrl-R> = ASCII 18     No      Yes     No
<DC3> = <Ctrl-S> = ASCII 19     Yes     Yes     No
<DC4> = <Ctrl-T> = ASCII 20     No      No      Yes
<NAK> = <Ctrl-U> = ASCII 21     Yes     No      Yes
<SYN> = <Ctrl-V> = ASCII 22     No      Yes     Yes
<ETB> = <Ctrl-W> = ASCII 23     Yes     Yes     Yes

<DC1>Text mode<DC2>Graphics mode<DC4>Serial port<ETB>

<SUB> = <Ctrl-Z> = ASCII 26

<BEL> = <Ctrl-G> = ASCII 7
Beep the speaker.