SYSLINUX Version 1.30 A bootloader for Linux using MS-DOS floppies Copyright (C) 1994-96 H. Peter Anvin This program is provided under the terms of the GNU General Public License, version 2 or, at your option, any later version. There is no warranty, neither expressed nor implied, to the function of this program. Please see the included file COPYING for details. SYSLINUX is a boot loader for the Linux operating system which operates off MS-DOS floppies. It is intended to simplify first-time installation of Linux. It is *not* intended to be used as a general purpose boot loader; once the operating system is installed I recommend LILO as the boot loader, except for people whose root filesystem is a UMSDOS filesystem (where a DOS defragmenter could wreck havoc with LILO's carefully set up block tables) -- for them I recommend Loadlin (which loads Linux from the DOS command line). SYSLINUX could, however, in conjunction with the UMSDOS filesystem, completely eliminate the need for distribution of raw diskette images for boot floppies. A SYSLINUX floppy can be manipulated using standard MS-DOS (or any other OS that can access an MS-DOS filesystem) tools once it has been created. ++++ CREATING A BOOTABLE LINUX FLOPPY +++ In order to create a bootable Linux floppy using SYSLINUX, prepare a normal MS-DOS formatted floppy. Copy one or more Linux kernel files to it, then execute the DOS command: SYSLINUX drive: This will alter the boot sector on the disk and copy a file named LDLINUX.SYS into its root directory. On boot time, by default, the kernel will be loaded from the image named LINUX on the boot floppy. This default can be changed, see the section on the SYSLINUX config file. If the Shift or Alt keys are held down during boot, or the Caps or Scroll locks are set, SYSLINUX will display a LILO-style "boot:" prompt. The user can then type a kernel file name followed by any kernel parameters. The SYSLINUX loader does not need to know about the kernel file in advance; all that is required is that it is a file located in the root directory on the disk. ++++ CONFIGURATION FILE ++++ All the configurable defaults in SYSLINUX can be changed by putting a file called SYSLINUX.CFG in the root directory of the boot floppy. This is a text file in either UNIX or DOS format, containing one or more of the following items (case is insensitive for keywords; upper case is used here to indicate that a word should be typed verbatim): DEFAULT kernel options... Sets the default command line. If SYSLINUX boots automatically, it will act just as if the entries after DEFAULT had been typed in at the "boot:" prompt, except that the option "auto" is automatically added, indicating an automatic boot. If no configuration file is present, or no DEFAULT entry is present in the config file, the default is kernel name "linux", with no options. 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. LABEL label KERNEL kernel APPEND options... Indicates that if "label" is entered as the kernel to boot, SYSLINUX should instead boot "kernel", and the specified APPEND options should be used instead of the ones specified in the global section of the file (before the first LABEL command.) The default for "kernel" is the same as "label", and if no APPEND is given the default is to use the global entry (if any). Up to 16 LABEL entries are permitted. Note that LILO uses the syntax: image = mykernel label = mylabel append = "myoptions" corresponding to the SYSLINUX: label mylabel kernel mykernel append myoptions APPEND - Append nothing. APPEND with a single hyphen as argument in a LABEL section can be used to override a global APPEND. 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. A timeout of zero will disable the timeout completely, this is also the default. NOTE: The maximum possible timeout value is 35996; corresponding to just below one hour. DISPLAY filename Displays the indicated file on the screen at boot time (before the boot: prompt, if displayed). This option takes the place of the LINUXMSG.TXT and BOOTMSG.TXT files in SYSLINUX 1.0. Please see the section below on DISPLAY files. NOTE: If the file is missing, this option is simply ignored. 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. This option takes the place of testing for the LINUXMSG.TXT file in SYSLINUX 1.0. F1 filename F2 filename ...etc... F9 filename F0 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.) Note that F10 MUST be entered in the config file as "F0", not "F10", and that there is currently no way to bind file names to F11 and F12. Please see the section below on DISPLAY files. Blank lines, and comment lines beginning with a hash mark (#) 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. The following combinations of options can be used to mimic the behaviour of SYSLINUX 1.0 with LINUXMSG.TXT or BOOTMSG.TXT present, respectively: # Mimic SYSLINUX 1.0 with LINUXMSG.TXT file present: display linuxmsg.txt prompt 1 # Mimic SYSLINUX 1.0 with BOOTMSG.TXT file present: display bootmsg.txt ++++ LARGE KERNELS AND INITIAL RAMDISK SUPPORT ++++ This version of SYSLINUX supports large kernels (bzImage format), eliminating the 500K size limit of the zImage kernel format. bzImage format kernels are detected automatically and handled transparently to the user. This version of SYSLINUX also supports a boottime-loaded ramdisk (initrd). An initrd is loaded from a DOS file if the option "initrd=filename" (where filename is the filename of the initrd image; the file must be located in the root directory on the boot floppy) is present on the processed command line (after APPEND's have been added, etc.). If several initrd options are present, the last one has precedence; this permits user-entered options to override a config file APPEND. Specifying "initrd=" without a filename inhibits initrd loading. The file specified by the initrd= option will typically be a gzipped filesystem image. NOTE: One of the main advantages with SYSLINUX is that it makes it very easy to support users with new or unexpected configurations, especially in a distribution setting. If initrd is used to extensively modularize the distribution kernel, it is strongly recommended that a simple way of adding drivers to the boot floppy be provided. The suggested manner is to let the initrd system mount the boot floppy and look for additional drivers in a predetermined location. To bzImage and recent zImage kernels, SYSLINUX 1.30 will identify using the ID byte 0x31. The ID range 0x32-0x3f is reserved for future versions of SYSLINUX. ++++ 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: = = 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 hex digits, 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. = = ASCII 26 End of file (DOS convention). ++++ NOVICE PROTECTION ++++ SYSLINUX will attempt to detect if the user is trying to boot on a 286 or lower class machine, or a machine with less than 608K of low ("DOS") RAM (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. The compile time and date of a specific SYSLINUX version can be obtained by the DOS command "type ldlinux.sys". This is also used as the signature for the LDLINUX.SYS file, which must match the boot sector. Any file that SYSLINUX uses can be marked hidden, system or readonly if so is convenient; SYSLINUX ignores all file attributes. The SYSLINUX installed automatically sets the readonly attribute on LDLINUX.SYS. ++++ BUG REPORTS ++++ I would appreciate hearing of any problems you have with SYSLINUX. I would also like to hear from you if you have successfully used SYSLINUX, *especially* if you are using it for a distribution. Please contact me at email . Sincerely, H. Peter Anvin November 2, 1996