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BOOT0CFG(8)			   BSD System Manager's Manual			      BOOT0CFG(8)

NAME
     boot0cfg -- boot manager installation/configuration utility

SYNOPSIS
     boot0cfg [-Bv] [-b boot0] [-d drive] [-e bell character] [-f file] [-i volume-id] [-m mask]
	      [-o options] [-s slice] [-t ticks] disk

DESCRIPTION
     The FreeBSD 'boot0' boot manager permits the operator to select from which disk and slice an
     i386 machine (PC) is booted.

     Note that what are referred to here as ``slices'' are typically called ``partitions'' in
     non-BSD documentation relating to the PC.	Typically, only non-removable disks are sliced.

     The boot0cfg utility optionally installs the 'boot0' boot manager on the specified disk; and
     allows various operational parameters to be configured.

     On PCs, a boot manager typically occupies sector 0 of a disk, which is known as the Master
     Boot Record (MBR).  The MBR contains both code (to which control is passed by the PC BIOS)
     and data (an embedded table of defined slices).

     The options are:

     -B      Install the 'boot0' boot manager.	This option causes MBR code to be replaced, with-
	     out affecting the embedded slice table.

     -b boot0
	     Specify which 'boot0' image to use.  The default is /boot/boot0 which will use the
	     video card as output, alternatively /boot/boot0sio can be used for output to the
	     COM1 port.  (Be aware that nothing will be output to the COM1 port unless the modem
	     signals DSR and CTS are active.)

     -d drive
	     Specify the drive number used by the PC BIOS in referencing the drive which contains
	     the specified disk.  Typically this will be 0x80 for the first hard drive, 0x81 for
	     the second hard drive, and so on; however any integer between 0 and 0xff is accept-
	     able here.

     -e bell character
	     Set the character to be printed in case of input error.

     -f file
	     Specify that a backup copy of the preexisting MBR should be written to file.  This
	     file is created if it does not exist, and replaced if it does.

     -i volume-id
	     Specifies a volume-id (in the form XXXX-XXXX) to be saved at location 0x1b8 in the
	     MBR. This information is sometimes used by NT, XP and Vista to identify the disk
	     drive. The option is only compatible with version 2.00 of the 512-byte boot block.

     -m mask
	     Specify slices to be enabled/disabled, where mask is an integer between 0 (no slices
	     enabled) and 0xf (all four slices enabled).

     -o options
	     A comma-separated string of any of the following options may be specified (with
	     ``no'' prepended as necessary):

	     packet  Use the disk packet (BIOS INT 0x13 extensions) interface, as opposed to the
		     legacy (CHS) interface, when doing disk I/O.  This allows booting above
		     cylinder 1023, but requires specific BIOS support.  The default is 'packet'.

	     setdrv  Forces the drive containing the disk to be referenced using drive number
		     definable by means of the -d option.  The default is 'nosetdrv'.

	     update  Allow the MBR to be updated by the boot manager.  (The MBR may be updated to
		     flag slices as 'active', and to save slice selection information.)  This is
		     the default; a 'noupdate' option causes the MBR to be treated as read-only.

     -s slice
	     Set the default boot selection to slice.  Values between 1 and 4 refer to slices; a
	     value of 5 refers to the option of booting from a second disk.

     -t ticks
	     Set the timeout value to ticks.  (There are approximately 18.2 ticks per second.)

     -v      Verbose: display information about the slices defined, etc.

NOTE
     Protection mechanisms in the geom(4) subsystem might prevent boot0cfg from being able to
     update the MBR on a mounted disk.	Instructions for temporarily disabling these protection
     mechanisms can be found in the geom(4) manpage. Specifically, do a

	   sysctl kern.geom.debugflags=0x10

     to allow writing to the MBR, and restore it to 0 afterwards.

FILES
     /boot/boot0     The default 'boot0' image
     /boot/boot0sio  Image for serial consoles (COM1,9600,8,N,1,MODEM)

EXIT STATUS
     The boot0cfg utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
     To boot slice 2 on the next boot:

	   boot0cfg -s 2 ad0

     To enable just slices 1 and 2 in the menu:

	   boot0cfg -m 0x3 ad0

     To go back to non-interactive booting, use fdisk(8) to install the default MBR:

	   fdisk -B ad0

SEE ALSO
     geom(4), boot(8), fdisk(8)

AUTHORS
     Robert Nordier <rnordier@FreeBSD.org>.

BUGS
     Use of the 'packet' option may cause 'boot0' to fail, depending on the nature of BIOS sup-
     port.

     Use of the 'setdrv' option with an incorrect -d operand may cause the boot0 code to write
     the MBR to the wrong disk, thus trashing its previous content.  Be careful.

BSD					 January 13, 2009				      BSD
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