= syslinux.cfg(5) = :doctype: manpage :revdate: 2012-10-28 :author: H. Peter Anvin :author-email: hpa@zytor.com :editor1: Gene Cumm :editor1-email: gene.cumm@gmail.com :editor1-revlast: 2012-10-28 :nbsp8:          :nbsp32: {nbsp8}{nbsp8}{nbsp8}{nbsp8} :data-uri: == NAME == syslinux.cfg - *Syslinux* configuration file == DESCRIPTION == Configuration for the boot behavior and user experience of *Syslinux* boot loaders, the format of display files and the boot prompt behavior. Blank lines are ignored. Note that the configuration file is not completely decoded. Syntax different from the one described above may still work correctly in this version of *Syslinux*, but may break in a future one. == LOCATION/NAME == *SYSLINUX* (before 4.00) used the configuration filename of syslinux.cfg. *EXTLINUX* (merged into *SYSLINUX* as of 4.00) used the filename extlinux.conf. Both default to searching for the config file in the installed directory (containing ldlinux.sys/extlinux.sys). As of 4.00, *SYSLINUX* will search for extlinux.conf then syslinux.cfg in each directory before falling back to the next directory. As of 3.35, *SYSLINUX* also searches /boot/syslinux, /syslinux and /. *ISOLINUX* (before 4.02) used the configuration filename of isolinux.cfg, searching /boot/isolinux (starting 2.00), then /isolinux and /. As of 4.02, *ISOLINUX* will search for isolinux.cfg then syslinux.cfg in /boot/isolinux before searching for the same files in /isolinux, /boot/syslinux, /syslinux, and /. == GLOBAL DIRECTIVES - MAIN == *#* comment:: A line comment. As of version 3.10, the space between the *#* and the comment is no longer required. *MENU* any string:: (3.00+) A directive for the simple menu system, treated as a comment outside the menu. See menu.txt. *INCLUDE* 'filename':: 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. *DEFAULT* 'kernel' 'options...':: 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. + If no configuration file is present, or no *DEFAULT* or *UI* entry is present in the config file, an error message is displayed and the 'boot:' prompt is shown (3.85+). *UI* 'module' 'options...':: 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. *LABEL* 'mylabel':: 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. + 'mylabel' must be unique. Currently the first instance is used but may result in an error or undesired behavior. 'mylabel' ends at the first character that is not a non-white-space printable character and should be restricted to non-white-space typeable characters. Prior to version 3.32, this would transformed to a DOS compatible format of 8.3 with a restricted character set. A *LABEL* clause must contain exactly 1 of the *KERNEL-LIKE DIRECTIVES* and may contain 1 each of the *LABEL-ONLY DIRECTIVES* or *DUAL-PURPOSE DIRECTIVES*. + Within a *LABEL*, using multiple *KERNEL-LIKE DIRECTIVES* or reuse of *LABEL-ONLY DIRECTIVES* or *DUAL-PURPOSE DIRECTIVES* will result in an override. Otherwise, multiple instances of the same directive will result in the last being effective. == DUAL-PURPOSE DIRECTIVES == Use of any of the *DUAL-PURPOSE DIRECTIVES* as *GLOBAL DIRECTIVES* is discouraged if there will be any non-Linux images loaded as *ALL* images will get these, including those manually entered at the 'boot:' prompt. *APPEND* 'options...':: 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. + Use of the parameter 'initrd=' supports multiple filenames separated by commas (ie 'initrd=initrd_file1,initrd_file2') within a single instance. This is mostly useful for initramfs, which can be composed of multiple separate cpio or cpio.gz archives. + Note: all initrd files except the last one are zero-padded to a 4K page boundary. This should not affect initramfs. + Note: Only the last effective 'initrd=' parameter is used for loading initrd files. *APPEND* -:: Append nothing. *APPEND* with a single hyphen as argument in a *LABEL* section can be used to override a global *APPEND*. //[FIXME: Shorten subdefinitions] *SYSAPPEND* 'bitmask':: *IPAPPEND* 'bitmask':: (*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: ifndef::doctype-manpage[[horizontal]] *1*::: An option of the following format should be generated, based on the input from the DHCP/BOOTP or PXE boot server and added to the kernel command line(see note below; empty for non-PXELINUX variants): + ---- ip=::: ---- + NOTE: The use of option 1 is no substitute for running a DHCP client in the booted system and should instead only be used to seed the client for a request. Without regular renewals, the lease acquired by the PXE BIOS will expire, making the IP address available for reuse by the DHCP server. + *2*::: An option of the following format should be generated, in dash-separated hexadecimal with leading hardware type (same as for the configuration file; see pxelinux.txt.) and added to the kernel command line, allowing an initrd program to determine from which interface the system booted(empty for non-PXELINUX variants): + ---- BOOTIF= ---- + *4*::: An option of the following format should be generated, in lower case hexadecimal in the format normally used for UUIDs (same as for the configuration file; see pxelinux.txt.) and added to the kernel command line: + ---- SYSUUID= ---- + *8*::: (5.10+) indicate the CPU family and certain particularly significant CPU feature bits: + ---- CPU= ---- + The is a single digit from 3 (i386) to 6 (i686 or higher.) The following CPU features are currently reported; additional flags may be added in the future: + .... P Physical Address Extension (PAE) V Intel Virtualization Technology (VT/VMX) T Intel Trusted Exection Technology (TXT/SMX) X Execution Disable (XD/NX) L Long Mode (x86-64) S AMD SMX virtualization .... + *DMI*::: (5.10+) The following strings are derived from DMI/SMBIOS information if available: + Bit String Significance ------------------------------------------------------------- 0x00010 SYSVENDOR= System vendor name 0x00020 SYSPRODUCT= System product name 0x00040 SYSVERSION= System version 0x00080 SYSSERIAL= System serial number 0x00100 SYSSKU= System SKU 0x00200 SYSFAMILY= System family 0x00400 MBVENDOR= Motherboard vendor name 0x00800 MBPRODUCT= Motherboard product name 0x01000 MBVERSION= Motherboard version 0x02000 MBSERIAL= Motherboard serial number 0x04000 MBASSET= Motherboard asset tag 0x08000 BIOSVENDOR= BIOS vendor name 0x10000 BIOSVERSION= BIOS version 0x20000 SYSFF= System form factor + If these strings contain white-space characters, they are replaced with underscores (_). + The system form factor value is a number defined in the SMBIOS specification, available at http://www.dmtf.org/. As of version 2.7.1 of the specification, the following values are defined: + 1 Other 2 Unknown 3 Desktop 4 Low profile desktop 5 Pizza box 6 Mini tower 7 Tower 8 Portble 9 Laptop 10 Notebook 11 Handheld 12 Docking station 13 All-in-one 14 Subnotebook 15 Space-saving 16 Lunch box 17 Main server chassis 18 Expansion chassis 19 Subchassis 20 Bus expansion chassis 21 Peripheral chassis 22 RAID chassis 23 Rack mount chasss 24 Sealed-case PC 25 Multi-system chassis 26 Compact PCI 27 Advanced TCI 28 Blade 29 Blade enclosure + *0x40000*::: (6.03+) Append a file system UUID string. For EXT2/3/4, this is the typical file system UUID. For FAT12/16/32, this is the 32-bit file system serial number (ie DA1A-0B2E). + ---- FSUUID= ---- == KERNEL-LIKE DIRECTIVES == // Alpha sort after KERNEL and LINUX *KERNEL* 'image':: Load a kernel-like file 'image' with automatic filetype detection based on file extension, listed under the non-auto-detecting directives, defaulting to *LINUX*. //[FIXME: Should "'image' as " be removed entirely or added to all? *LINUX* is used as an example] *LINUX* 'image':: Load 'image' as a Linux-like kernel. MEMDISK is an example of a non-Linux kernel loaded in a Linux-like fashion. *BOOT* 'image':: (*ISOLINUX* only: .bin; *SYSLINUX* only: .bs) Load a boot sector. .bin is a "CD boot sector" and .bs is a regular disk boot sector. *BSS* 'image':: (*SYSLINUX* only: .bss) Load a BSS image, a .bs image with the DOS superblock patched in. *COMBOOT* 'image':: (.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* *COM32* 'image':: (.c32) Load a *Syslinux* COM32 (32-bit *COMBOOT*) image. See also *comboot.txt* *CONFIG* 'image':: 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. *FDIMAGE* 'image':: (Removed as of 4.05, added 1.65; *ISOLINUX* only: .img) Load a disk image. *LOCALBOOT* 'type':: (*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. + On *PXELINUX*, 'type' 0 means perform a normal boot. 'type' 4 will perform a local boot with the Universal Network Driver Interface (UNDI) driver still resident in memory. Finally, 'type' 5 will perform a local boot with the entire PXE stack, including the UNDI driver, still resident in memory. All other values are undefined. If you don't know what the UNDI or PXE stacks are, don't worry -- you don't want them, just specify 0. + On *ISOLINUX*/*SYSLINUX*, the 'type' specifies the local drive number to boot from; 0x00 is the primary floppy drive and 0x80 is the primary hard drive. *PXE* 'image':: (*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. == LABEL-ONLY DIRECTIVES == *INITRD* 'initrd_file':: (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*). == GLOBAL DIRECTIVES - SECONDARY == These are global directives that are of lesser importance, often affecting the user experience and not the boot process. *ALLOWOPTIONS* 'flag_val':: 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. *IMPLICIT* 'flag_val':: 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. *TIMEOUT* 'timeout':: 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. *TOTALTIMEOUT* 'timeout':: 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. + Both *TIMEOUT* and *TOTALTIMEOUT* can be used together, for example: + ---- # Wait 5 seconds unless the user types something, but # always boot after 15 minutes. TIMEOUT 50 TOTALTIMEOUT 9000 ---- // FIXME: be consistent *ONTIMEOUT* 'kernel options...':: Sets the command line invoked on a timeout (which often references a LABEL). If not specified, 'UI' (if used) or 'DEFAULT is used. *ONERROR* 'kernel options...':: 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 ---- + and the command line as entered by the user is: + ---- foo bar baz ---- + *Syslinux* will execute the following as if entered by the user: + ---- xyzzy plugh foo bar baz ---- *SERIAL* 'port [baudrate [flowcontrol]]':: 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. + 'flowcontrol' is a combination of the following bits: + .... 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 .... + All other bits are reserved. + Typical values are: + .... 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 .... + For the *SERIAL* directive to be guaranteed to work properly, it should be the first directive in the configuration file. + NOTE: 'port' values from 0 to 3 means the first four serial ports detected by the BIOS. They may or may not correspond to the legacy port values 0x3F8, 0x2F8, 0x3E8, 0x2E8. + Enabling interrupts (setting the 0x008 bit) may give better responsiveness without setting the *NOHALT* option, but could potentially cause problems with buggy BIOSes. + This option is "sticky" and is not automatically reset when loading a new configuration file with the CONFIG command. *NOHALT* 'flag_val':: 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. *CONSOLE* 'flag_val':: 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.) + Some BIOSes try to forward this to the serial console and sometimes make a total mess thereof, so this option lets you disable the video console on these systems. *FONT* 'filename':: 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. *KBDMAP* 'keymap':: 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.) + The included program keytab-lilo.pl from the LILO distribution can be used to create such keymaps. The file keytab-lilo.txt contains the documentation for this program. *DISPLAY* 'filename':: Displays the indicated file on the screen at boot time (before the boot: prompt, if displayed). Please see the section below on *DISPLAY* files. + NOTE: If the file is missing, this option is simply ignored. *SAY* 'message':: Prints the message on the screen. *PROMPT* 'flag_val':: 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. *NOESCAPE* 'flag_val':: 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. *NOCOMPLETE* 'flag_val':: If 'flag_val' is set to 1, the Tab key does not display labels at the boot: prompt. // ...etc... *F1* 'filename':: *F2* 'filename':: *F3* 'filename':: *F4* 'filename':: *F5* 'filename':: *F6* 'filename':: *F7* 'filename':: *F8* 'filename':: *F9* 'filename':: *F10* 'filename':: *F11* 'filename':: *F12* 'filename':: 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. + When using the serial console, press to get to the help screens, e.g. <2> to get to the F2 screen. For F10-F12, hit , B, C. For compatibility with earlier versions, F10 can also be entered as 0. *PATH* 'path':: (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. *SENDCOOKIES* 'bitmask':: (*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. + This command limits the cookies send; 0 means no cookies. The default is -1, meaning send all cookies. + This option is "sticky" and is not automatically reset when loading a new configuration file with the CONFIG command. == DISPLAY FILE FORMAT == DISPLAY and function-key help files are text files in either DOS or UNIX format (with or without ). In addition, the following special codes are interpreted: //[FIXME]: #1 doesn't break; #2 as-is; #3 broken but not on right; #4 identical to #3 // horizontal extends the line's label, reducing the definition // tab or space to shift explanation ? align beginning or end? // ifndef::doctype-manpage[[horizontal]] **:: {nbsp32} = = ASCII 12 + Clear the screen, home the cursor. Note that the screen is filled with the current display color. **:: = = ASCII 12; Clear the screen, home the cursor. Note that the screen is filled with the current display color. **:: = = ASCII 12 + Clear the screen, home the cursor. Note that the screen is filled with the current display color. **:: = = ASCII 12 + Clear the screen, home the cursor. Note that the screen is filled with the current display color. **'':: = = ASCII 15 + Set the display colors to the specified background and foreground colors, where and are the 2 hex digits representing 1 byte, corresponding to the standard PC display attributes: + 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 + Picking a bright color (8-f) for the background results in the corresponding dark color (0-7), with the foreground flashing. + Colors are not visible over the serial console. **'filename':: = = ASCII 24 + If a VGA display is present, enter graphics mode and display the graphic included in the specified file. The file format is an ad hoc format called LSS16; the included Perl program "ppmtolss16" can be used to produce these images. This Perl program also includes the file format specification. + The image is displayed in 640x480 16-color mode. Once in graphics mode, the display attributes (set by code sequences) work slightly differently: the background color is ignored, and the foreground colors are the 16 colors specified in the image file. For that reason, ppmtolss16 allows you to specify that certain colors should be assigned to specific color indicies. + Color indicies 0 and 7, in particular, should be chosen with care: 0 is the background color, and 7 is the color used for the text printed by *Syslinux* itself. **:: = = ASCII 25 + If we are currently in graphics mode, return to text mode. **..**:: .. = ASCII 16-23 + These codes can be used to select which modes to print a certain part of the message file in. Each of these control characters select a specific set of modes (text screen, graphics screen, serial port) for which the output is actually displayed: + Character Text Graph Serial ------------------------------------------------------ = = ASCII 16 No No No = = ASCII 17 Yes No No = = ASCII 18 No Yes No = = ASCII 19 Yes Yes No = = ASCII 20 No No Yes = = ASCII 21 Yes No Yes = = ASCII 22 No Yes Yes = = ASCII 23 Yes Yes Yes + For example, the following will actually print out which mode the console is in: + Text modeGraphics modeSerial port **:: = = ASCII 26 + End of file (DOS convention). **:: = = ASCII 7 + Beep the speaker. == BOOT LOADER IDS USED == The Linux boot protocol supports a "boot loader ID", a single byte where the upper nybble specifies a boot loader family (3 = *Syslinux*) and the lower nybble is version or, in the case of *Syslinux*, media: 0x31 (49) = SYSLINUX 0x32 (50) = PXELINUX 0x33 (51) = ISOLINUX 0x34 (52) = EXTLINUX In recent versions of Linux, this ID is available as /proc/sys/kernel/bootloader_type. == NOVICE PROTECTION == *Syslinux* will attempt to detect booting on a machine with too little memory, which means the Linux boot sequence cannot complete. If so, a message is displayed and the boot sequence aborted. Holding down the Ctrl key while booting disables this feature. Any file that *Syslinux* uses can be marked hidden, system or readonly if so is convenient; *Syslinux* ignores all file attributes. The *SYSLINUX* installer automatically sets the readonly/hidden/system attributes on LDLINUX.SYS. == EXAMPLE == Here are some sample config files: ---- # SERIAL 0 115200 DEFAULT linux PROMPT 1 TIMEOUT 600 LABEL linux LINUX vmlinuz APPEND initrd=initrd1.gz,initrd2.gz LABEL m COM32 menu.c32 ---- In this example, serial port use is disabled but can be enabled by uncommenting the first line and utilize serial port 0 at 115200 bps. If 'linux' is typed on the command line, the kernel-like file 'vmlinuz' is executed as a Linux kernel, initrd files initrd1.gz and initrd2.gz are loaded as initial ramdisk files (like cpio.gz files for initramfs). If 'm' is typed on the command line, the COM32 module 'menu.c32' is executed to launch a menu system. == KNOWN BUGS == include::com-bug.txt[] == BUG REPORTS == include::com-rpt.txt[] == AUTHOR == This AsciiDoc derived document is a modified version of the original *SYSLINUX* documentation by {author} <{author-email}>. The conversion to an AsciiDoc was made by {editor1} <{editor1-email}>