bootmenu.doc

又一个选择启动分区的程序源码

	BOOTMENU -- a BOOT sector program with a MENU
	---------------------------------------------
		by Gordon W. Ross, Aug 1990

	This program is loaded by the PC ROM BIOS and is responsible
	for selecting one of four partitions to boot from.  The normal
	(MS-DOS) version of this program always boots the "active"
	partition, but this version allows any partition to be
	selected for booting, wether marked "active" or not.

	Two versions of this program are now distributed:

	BOOTMENU is small (less than 256 bytes of code) and compatible
	with the SpeedStor hard disk formatting package.  (Note that
	SpeedStor writes in several locations in the boot sector!)
	This version, however, does not allow unattended reboots.
	After BOOTMENU displays its partition menu, it waits
	indefinitely for someone to select a boot partition.

	BOOTAUTO (previously called "boot-hdp") is a full-featured
	boot program which allows boot-time partition selection, but
	also provides a default selection which is used if no user
	input arrives within five seconds.

	The behaviour of BOOTAUTO is as follows:

	BOOTAUTO displays the message:
		Booting device: hd0,
	and then pauses for a five second delay.

	If the user presses any key before the delay expires, a menu
	of bootable partitions is displayed, and the user is prompted
	for the number of the partition to boot from.  If no key is
	pressed before the delay ends, the first partition marked as
	"active" is used.  If no partition is marked as active, the
	boot menu is presented without delay, as if a key were struck.
	In essence, this program interprets the "active" mark (if
	present) as a default choice indicator.

	Once a partition has been selected this program displays the
	selected partition number and loads its secondary boot
	program.  Errors are printed if (1) the selected partition is
	empty, (2) the secondary boot program lacks a valid signature,
	or (3) an error occurs while reading the secondary boot sector.

	Installation:
	------------
	The "pfdisk" utility included with this program simplifies
	installation of BOOTAUTO into the primary boot sector.
	Instructions for using "pfdisk" are in the pfdisk.doc file.

	Limitations:
	-----------
	Names in the boot menu:

	BOOTMENU and BOOTAUTO contain a name table that is used to
	generate the boot menu.  This name table is recognized (using
	a signature) and updated by pfdisk but not by other fdisk
	programs. If another fdisk program is used to modify the
	partition table, the name table may be left with misleading
	entries.  Note that pfdisk only updates the name field for any
	entry when the entry is set using the optional name field, i.e:

		pfdisk> 1 4 0 127 MS-LOSS

	Furthermore, the name supplied as the fourth arg. is truncated
	to eight characters.  (Space is tight in the boot sector.)

	The signature which flags the presence of a name table is
	written into any boot sector every time the name argument is
	given in a partition setting command (1,2,3,4).  This
	signature occupies locations 0x1A0 -- 0x1AD which does not
	clobber anything used by any of: UNIX or DOS boot programs,
	SpeedStor or WesternDigital Auto-configuring controllers.

	Booting inactive partitions:

	MS-DOS will boot from an inactive partition without needing
	any modifications.  Unfortunately, some systems refuse to boot
	from a partition which is not marked as active.

	ESIX (from Everex Systems) Sys.V Rel.3.2 will not (as shipped)
	boot unless its partition is marked active.  Other versions of
	Sys.V/386 are similar in this regard.  The easiest solution is
	to mark the UNIX partition as active, and use BOOTMENU to
	offer you a choice between DOS and UNIX.

	If you wish, it is also possible to patch UNIX so that it will
	boot without demanding that its partition be marked active.
	These patches (called "esix-boot") are available from the
	author.  Send EMAIL to [e-mail] if you want them.