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1 .\" Copyright (c) 1999 Robert Nordier
2 .\" All rights reserved.
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25 .\" $FreeBSD: src/usr.sbin/boot0cfg/boot0cfg.8,v 1.5.2.6 2003/03/12 22:08:13 trhodes Exp $
26 .\" $DragonFly: src/usr.sbin/boot0cfg/boot0cfg.8,v 1.4 2008/03/24 23:04:19 swildner Exp $
27 .\"
28 .Dd March 23, 2008
29 .Dt BOOT0CFG 8
30 .Os
31 .Sh NAME
32 .Nm boot0cfg
33 .Nd boot manager installation/configuration utility
34 .Sh SYNOPSIS
35 .Nm
36 .Op Fl Bv
37 .Op Fl b Ar boot0
38 .Op Fl d Ar drive
39 .Op Fl f Ar file
40 .Op Fl m Ar mask
41 .Op Fl o Ar options
42 .Op Fl s Ar slice
43 .Op Fl t Ar ticks
44 .Ar disk
45 .Sh DESCRIPTION
46 The
47 .Dx
48 .Sq boot0
49 boot manager permits the operator to select from which disk and
50 slice an i386 machine (PC) is booted.
51 .Pp
52 Note that what are referred to here as
53 .Dq slices
54 are typically called
55 .Dq partitions
56 in
57 .No non- Ns Bx
58 documentation relating to the PC.
59 Typically, only non-removable disks are sliced.
60 .Pp
61 The
62 .Nm
63 utility optionally installs the
64 .Sq boot0
65 boot manager on the specified
66 .Ar disk ;
67 and allows various operational parameters to be configured.
68 .Pp
69 On PCs, a boot manager typically occupies sector 0 of a disk, which is
70 known as the Master Boot Record (MBR).
71 The MBR contains both code (to which control is passed by the PC BIOS)
72 and data (an embedded table of defined slices).
73 .Pp
74 The options are:
75 .Bl -tag -width indent
76 .It Fl B
77 Install the
78 .Sq boot0
79 boot manager.
80 This option causes MBR code to be replaced, without
81 affecting the embedded slice table.
82 .It Fl b Ar boot0
83 Specify which
84 .Sq boot0
85 image to use.
86 The default is
87 .Pa /boot/boot0 .
88 .It Fl d Ar drive
89 Specify the drive number used by the PC BIOS in referencing the drive
90 which contains the specified
91 .Ar disk .
92 Typically this will be 0x80 for the first hard drive, 0x81 for the
93 second hard drive, and so on; however any integer between 0 and 0xff
94 is acceptable here.
95 .It Fl f Ar file
96 Specify that a backup copy of the preexisting MBR should be written to
97 .Ar file .
98 This file is created if it does not exist, and replaced if it does.
99 .It Fl m Ar mask
100 Specify slices to be enabled/disabled, where
101 .Ar mask
102 is an integer between 0 (no slices enabled) and 0xf (all four slices
103 enabled).
104 .It Fl o Ar options
105 A comma-separated string of any of the following options may be
106 specified (with
107 .Dq no
108 prepended as necessary):
109 .Bl -tag -width indent
110 .It packet
111 Use the disk packet (BIOS INT 0x13 extensions) interface,
112 as opposed to the legacy (CHS) interface, when doing disk I/O.
113 This allows booting above cylinder 1023, but requires specific
114 BIOS support.
115 The default is
116 .Sq nopacket .
117 .It setdrv
118 Forces the drive containing the disk to be referenced using drive
119 number definable by means of the -d option.
120 The default is
121 .Sq nosetdrv .
122 .It update
123 Allow the MBR to be updated by the boot manager.
124 (The MBR may be updated to flag slices as
125 .Sq active ,
126 and to save slice selection information.)
127 This is the default; a
128 .Sq noupdate
129 option causes the MBR to be treated as read-only.
130 .El
131 .It Fl s Ar slice
132 Set the default boot selection to
133 .Ar slice .
134 Values between 1 and 4 refer to slices; a value of 5 refers to the
135 option of booting from a second disk.
136 .It Fl t Ar ticks
137 Set the timeout value to
138 .Ar ticks .
139 (There are approximately 18.2 ticks per second.)
140 .It Fl v
141 Verbose: display information about the slices defined, etc.
142 .El
143 .Sh FILES
144 .Bl -tag -width /boot/boot0 -compact
145 .It Pa /boot/boot0
146 The default
147 .Sq boot0
148 image
149 .El
150 .Sh EXIT STATUS
151 .Ex -std
152 .Sh EXAMPLES
153 To boot slice 2 on the next boot:
154 .Pp
155 .Dl "boot0cfg -s 2 ad0"
156 .Pp
157 To enable just slices 1 and 2 in the menu:
158 .Pp
159 .Dl "boot0cfg -m 0x3 ad0"
160 .Pp
161 To go back to non-interactive booting, use
162 .Xr fdisk 8
163 to install the default MBR:
164 .Pp
165 .Dl "fdisk -B ad0"
166 .Sh SEE ALSO
167 .Xr boot 8 ,
168 .Xr fdisk 8
169 .Sh AUTHORS
170 .An Robert Nordier Aq rnordier@FreeBSD.org .
171 .Sh BUGS
172 Use of the
173 .Sq packet
174 option may cause
175 .Sq boot0
176 to fail, depending on the nature of BIOS support.
177 .Pp
178 Use of the
179 .Sq setdrv
180 option with an incorrect -d operand may cause the MBR to be written
181 to the wrong disk.
182 Be careful!