1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software written and contributed 5.\" to Berkeley by William Jolitz. 6.\" 7.\" Almost completely rewritten for FreeBSD 2.1 by Joerg Wunsch. 8.\" 9.\" Substantially revised for FreeBSD 3.1 by Robert Nordier. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94 36.\" 37.\" $FreeBSD$ 38.\" 39.Dd July 1, 2013 40.Dt BOOT 8 i386 41.Os 42.Sh NAME 43.Nm boot 44.Nd system bootstrapping procedures 45.Sh DESCRIPTION 46.Sy Power fail and crash recovery . 47Normally, the system will reboot itself at power-up or after crashes. 48An automatic consistency check of the file systems will be performed, 49and unless this fails, the system will resume multi-user operations. 50.Pp 51.Sy Cold starts . 52Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes 53known as drive A:) and, failing that, from hard disk drive 0 (sometimes 54known as drive C:, or as drive 0x80 to the BIOS). 55Some BIOSes allow 56you to change this default sequence, and may also include a CD-ROM 57drive as a boot device. 58.Pp 59By default, a three-stage bootstrap is employed, and control is 60automatically passed from the boot blocks (bootstrap stages one and 61two) to a separate third-stage bootstrap program, 62.Xr loader 8 . 63This third stage provides more sophisticated control over the booting 64process than it is possible to achieve in the boot blocks, which are 65constrained by occupying limited fixed space on a given disk or slice. 66.Pp 67However, it is possible to dispense with the third stage altogether, 68either by specifying a kernel name in the boot block parameter 69file, 70.Pa /boot.config , 71or, unless option 72.Fl n 73is set, by hitting a key during a brief pause (while one of the characters 74.Sy - , 75.Sy \e , 76.Sy \&| , 77or 78.Sy / 79is displayed) before 80.Xr loader 8 81is invoked. 82Booting will also be attempted at stage two, if the 83third stage cannot be loaded. 84.Pp 85The remainder of this subsection deals only with the boot blocks. 86The 87.Xr loader 8 88program is documented separately. 89.Pp 90After the boot blocks have been loaded, 91you should see a prompt similar to the following: 92.Bd -literal 93>> FreeBSD/i386 BOOT 94Default: 0:ad(0,a)/boot/loader 95boot: 96.Ed 97.Pp 98The automatic boot will attempt to load 99.Pa /boot/loader 100from partition 101.Ql a 102of either the floppy or the hard disk. 103This boot may be aborted by typing any character on the keyboard 104at the 105.Ql boot: 106prompt. 107At this time, the following input will be accepted: 108.Bl -tag -width indent 109.It Ic \&? 110Give a short listing of the files in the root directory of the default 111boot device, as a hint about available boot files. 112(A 113.Ic ?\& 114may also be specified as the last segment of a path, in which case 115the listing will be of the relevant subdirectory.) 116.It Xo 117.Sm off 118.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 119.Ar filename 120.Sm on 121.Op Fl aCcDdghmnPprsv 122.Op Fl S Ns Ar speed 123.Xc 124Specify boot file and flags. 125.Bl -tag -width indent 126.It Ar bios_drive 127The drive number as recognized by the BIOS. 1280 for the first drive, 1 for the second drive, etc. 129.It Ar interface 130The type of controller to boot from. 131Note that the controller is required 132to have BIOS support since the BIOS services are used to load the 133boot file image. 134.Pp 135The supported interfaces are: 136.Pp 137.Bl -tag -width "adXX" -compact 138.It ad 139ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 140controller 141.It fd 1425 1/4" or 3 1/2" High density floppies 143.It da 144SCSI disk on any supported SCSI controller 145.\".It cd 146.\"boot from CDROM 147.El 148.It Ar unit 149The unit number of the drive on the interface being used. 1500 for the first drive, 1 for the second drive, etc. 151.It Oo Ar slice , Oc Ns Ar part 152The partition letter inside the 153.Bx 154portion of the disk. 155See 156.Xr bsdlabel 8 . 157By convention, only partition 158.Ql a 159contains a bootable image. 160If sliced disks are used 161.Pq Dq fdisk partitions , 162any 163.Ar slice 164(1 for the first slice, 2 for the second slice, etc.\&) 165can be booted from, with the default (if not specified) being the active slice 166or, otherwise, the first 167.Fx 168slice. 169If 170.Ar slice 171is specified as 0, the first 172.Fx 173slice (also known as 174.Dq compatibility 175slice) is booted from. 176.It Ar filename 177The pathname of the file to boot (relative to the root directory 178on the specified partition). 179Defaults to 180.Pa /boot/kernel/kernel . 181Symbolic links are not supported (hard links are). 182.It Xo Op Fl aCcDdghmnPpqrsv 183.Op Fl S Ns Ar speed 184.Xc 185Boot flags: 186.Pp 187.Bl -tag -width "-CXX" -compact 188.It Fl a 189during kernel initialization, 190ask for the device to mount as the root file system. 191.It Fl C 192try to mount root file system from a CD-ROM. 193.It Fl c 194this flag is currently a no-op. 195.It Fl D 196boot with the dual console configuration. 197In the single 198configuration, the console will be either the internal display 199or the serial port, depending on the state of the 200.Fl h 201option below. 202In the dual console configuration, 203both the internal display and the serial port will become the console 204at the same time, regardless of the state of the 205.Fl h 206option. 207.It Fl d 208enter the DDB kernel debugger 209(see 210.Xr ddb 4 ) 211as early as possible in kernel initialization. 212.It Fl g 213use the GDB remote debugging protocol. 214.It Fl h 215force the serial console. 216For instance, if you boot from the internal console, 217you can use the 218.Fl h 219option to force the kernel to use the serial port as its 220console device. 221The serial port driver 222.Xr sio 4 223(but not 224.Xr uart 4 ) 225has a flag (0x20) to override this option. 226If that flag is set, the serial port will always be used as the console, 227regardless of the 228.Fl h 229option described here. 230.It Fl m 231mute the console to suppress all console input and output during the 232boot. 233.It Fl n 234ignore key press to interrupt boot before 235.Xr loader 8 236is invoked. 237.It Fl P 238probe the keyboard. 239If no keyboard is found, the 240.Fl D 241and 242.Fl h 243options are automatically set. 244.It Fl p 245pause after each attached device during the device probing phase. 246.It Fl q 247be quiet, 248do not write anything to the console unless automatic boot fails or 249is disabled. 250This option only affects second-stage bootstrap, 251to prevent next stages from writing to the console use in 252combination with the 253.Fl m 254option. 255.It Fl r 256use the statically configured default for the device containing the 257root file system 258(see 259.Xr config 8 ) . 260Normally, the root file system is on the device 261that the kernel was loaded from. 262.It Fl s 263boot into single-user mode; if the console is marked as 264.Dq insecure 265(see 266.Xr ttys 5 ) , 267the root password must be entered. 268.It Fl S Ns Ar speed 269set the speed of the serial console to 270.Ar speed . 271The default is 9600 unless it has been overridden by setting 272.Va BOOT_COMCONSOLE_SPEED 273in 274.Xr make.conf 5 275and recompiling and reinstalling the boot blocks. 276.It Fl v 277be verbose during device probing (and later). 278.El 279.El 280.El 281.Pp 282Use the 283.Pa /boot.config 284file to set the default configuration options for the boot block code. 285See 286.Xr boot.config 5 287for more information about the 288.Pa /boot.config 289file. 290.Sh FILES 291.Bl -tag -width /boot/loader -compact 292.It Pa /boot.config 293parameters for the boot blocks (optional) 294.It Pa /boot/boot1 295first stage bootstrap file 296.It Pa /boot/boot2 297second stage bootstrap file 298.It Pa /boot/loader 299third stage bootstrap 300.It Pa /boot/kernel/kernel 301default kernel 302.It Pa /boot/kernel.old/kernel 303typical non-default kernel (optional) 304.El 305.Sh DIAGNOSTICS 306When disk-related errors occur, these are reported by the second-stage 307bootstrap using the same error codes returned by the BIOS, for example 308.Dq Disk error 0x1 (lba=0x12345678) . 309Here is a partial list of these error codes: 310.Pp 311.Bl -tag -width "0x80" -compact 312.It 0x1 313Invalid argument 314.It 0x2 315Address mark not found 316.It 0x4 317Sector not found 318.It 0x8 319DMA overrun 320.It 0x9 321DMA attempt across 64K boundary 322.It 0xc 323Invalid media 324.It 0x10 325Uncorrectable CRC/ECC error 326.It 0x20 327Controller failure 328.It 0x40 329Seek failed 330.It 0x80 331Timeout 332.El 333.Pp 334.Sy "NOTE" : 335On older machines, or otherwise where EDD support (disk packet 336interface support) is not available, all boot-related files and 337structures (including the kernel) that need to be accessed during the 338boot phase must reside on the disk at or below cylinder 1023 (as the 339BIOS understands the geometry). 340When a 341.Dq Disk error 0x1 342is reported by the second-stage bootstrap, it generally means that this 343requirement has not been adhered to. 344.Sh SEE ALSO 345.Xr ddb 4 , 346.Xr boot.config 5 , 347.Xr make.conf 5 , 348.Xr ttys 5 , 349.Xr boot0cfg 8 , 350.Xr bsdlabel 8 , 351.Xr btxld 8 , 352.Xr config 8 , 353.Xr gptboot 8 , 354.Xr halt 8 , 355.Xr loader 8 , 356.Xr nextboot 8 , 357.Xr reboot 8 , 358.Xr shutdown 8 359.Sh BUGS 360The bsdlabel format used by this version of 361.Bx 362is quite 363different from that of other architectures. 364.Pp 365Due to space constraints, the keyboard probe initiated by the 366.Fl P 367option is simply a test that the BIOS has detected an 368.Dq extended 369keyboard. 370If an 371.Dq XT/AT 372keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 373fail. 374