1 .\" Copyright (c) 1999 Robert Nordier
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32 .Nd boot manager installation/configuration utility
38 .Op Fl e Ar bell character
50 boot manager permits the operator to select from which disk and
51 slice an i386 machine (PC) is booted.
53 Note that what are referred to here as
59 documentation relating to the PC.
60 Typically, only non-removable disks are sliced.
64 utility optionally installs the
66 boot manager on the specified
68 and allows various operational parameters to be configured.
70 On PCs, a boot manager typically occupies sector 0 of a disk, which is
71 known as the Master Boot Record (MBR).
72 The MBR contains both code (to which control is passed by the PC BIOS)
73 and data (an embedded table of defined slices).
76 .Bl -tag -width indent
81 This option causes MBR code to be replaced, without
82 affecting the embedded slice table.
89 which will use the video card as output, alternatively
91 can be used for output to the COM1 port.
92 (Be aware that nothing will be output to the COM1 port unless the
93 modem signals DSR and CTS are active.)
95 Specify the drive number used by the PC BIOS in referencing the drive
96 which contains the specified
98 Typically this will be 0x80 for the first hard drive, 0x81 for the
99 second hard drive, and so on; however any integer between 0 and 0xff
101 .It Fl e Ar bell character
102 Set the character to be printed in case of input error.
104 Specify that a backup copy of the preexisting MBR should be written to
106 This file is created if it does not exist, and replaced if it does.
107 .It Fl i Ar volume-id
108 Specifies a volume-id (in the form XXXX-XXXX) to be saved at location
109 0x1b8 in the MBR. This information is sometimes used by NT, XP and Vista
110 to identify the disk drive. The option is only compatible with version 2.00
111 of the 512-byte boot block.
113 Specify slices to be enabled/disabled, where
115 is an integer between 0 (no slices enabled) and 0xf (all four slices
118 A comma-separated string of any of the following options may be
121 prepended as necessary):
122 .Bl -tag -width indent
124 Use the disk packet (BIOS INT 0x13 extensions) interface,
125 as opposed to the legacy (CHS) interface, when doing disk I/O.
126 This allows booting above cylinder 1023, but requires specific
131 Forces the drive containing the disk to be referenced using drive
132 number definable by means of the -d option.
136 Allow the MBR to be updated by the boot manager.
137 (The MBR may be updated to flag slices as
139 and to save slice selection information.)
140 This is the default; a
142 option causes the MBR to be treated as read-only.
145 Set the default boot selection to
147 Values between 1 and 4 refer to slices; a value of 5 refers to the
148 option of booting from a second disk.
150 Set the timeout value to
152 (There are approximately 18.2 ticks per second.)
154 Verbose: display information about the slices defined, etc.
157 Protection mechanisms in the
159 subsystem might prevent
161 from being able to update the MBR on a mounted disk.
162 Instructions for temporarily disabling these protection mechanisms
165 manpage. Specifically, do a
167 .Dl sysctl kern.geom.debugflags=0x10
169 to allow writing to the MBR, and restore it to 0 afterwards.
172 .Bl -tag -width /boot/boot0sio -compact
177 .It Pa /boot/boot0sio
178 Image for serial consoles (COM1,9600,8,N,1,MODEM)
183 To boot slice 2 on the next boot:
185 .Dl "boot0cfg -s 2 ad0"
187 To enable just slices 1 and 2 in the menu:
189 .Dl "boot0cfg -m 0x3 ad0"
191 To go back to non-interactive booting, use
193 to install the default MBR:
202 .An Robert Nordier Aq rnordier@FreeBSD.org .
208 to fail, depending on the nature of BIOS support.
212 option with an incorrect -d operand may cause the boot0 code
213 to write the MBR to the wrong disk, thus trashing its previous