boot(8)
- NetBSD Manual Pages
BOOT(8) NetBSD/i386 System Manager's Manual BOOT(8)
NAME
boot -- system bootstrapping procedures
DESCRIPTION
IA-32 computers (the IBM PC and its clones) that can run NetBSD/i386 can
use any of the following boot procedures, depending on what the hardware
and BIOS support:
boot bootstrap NetBSD from the system BIOS
dosboot(8) bootstrap NetBSD from MS-DOS
w95boot(8) bootstrap NetBSD from Windows 95
pxeboot(8) network bootstrap NetBSD from a TCP/IP LAN with DHCP, TFTP,
and NFS.
Power fail and crash recovery
Normally, the system will reboot itself at power-up or after crashes. An
automatic consistency check of the file systems will be performed, and
unless this fails, the system will resume multi-user operations.
Cold starts
The 386 PC AT clones attempt to boot the floppy disk drive A (otherwise
known as drive 0) first, and failing that, attempt to boot the hard disk
C (otherwise known as hard disk controller 1, drive 0). The NetBSD boot-
blocks are loaded and started either by the BIOS, or by a boot selector
program (such as OS-BS, BOOTEASY, the OS/2 Boot Menu or NetBSD's
boot-selecting master boot record - see mbr(8)).
Normal Operation
Once running, a banner similar to the following will appear:
>> NetBSD BIOS Boot, revision 3.0
>> (user@buildhost, builddate)
>> Memory: 637/15360 k
Press return to boot now, any other key for boot menu
booting hd0a:netbsd - starting in 5
After a countdown, the system image listed will be loaded. In the exam-
ple above, it will be ``hd0a:netbsd'' which is the file netbsd on parti-
tion ``a'' of the NetBSD MBR partition of the first hard disk known to
the BIOS (which is an IDE or similar device - see the BUGS section).
Pressing a key within the time limit, or before the boot program starts,
will enter interactive mode. When using a short or 0 timeout, it is
often useful to interrupt the boot by holding down a shift key, as some
BIOSes and BIOS extensions will drain the keystroke buffer at various
points during POST.
Diagnostic Output
If the first stage boot fails to load the boot, it will print a terse
message indicating the reason for the failure. The possible error mes-
sages and their cause are listed in mbr(8).
If the first stage boot succeeds, the banner will be shown and the error
messages should be self-explanatory.
Interactive mode
In interactive mode, the boot loader will present a prompt, allowing
input of these commands:
boot [device:][filename] [-acdqsv]
The default device will be set to the disk that the boot loader
was loaded from. To boot from an alternate disk, the full name
of the device should be given at the prompt. device is of the
form xd [N[x]] where xd is the device from which to boot, N is
the unit number, and x is the partition letter.
The following list of supported devices may vary from installa-
tion to installation:
hd Hard disks as numbered by the BIOS. This includes
ST506, IDE, ESDI, RLL disks on a WD100[2367] or looka-
like controller(s), and SCSI disks on SCSI controllers
recognized by the BIOS.
fd Floppy drives as numbered by the BIOS.
The default filename is netbsd; if the boot loader fails to
successfully open that image, it then tries netbsd.gz (expected
to be a kernel image compressed by gzip), followed by
netbsd.old, netbsd.old.gz, onetbsd, and finally onetbsd.gz.
Alternate system images can be loaded by just specifying the
name of the image.
Options are:
-a Prompt for the root file system device, the system crash
dump device, and the path to init(8).
-c Bring the system up into the device configuration manager.
From here the device locators can be tuned to the hard-
ware; see userconf(4).
-d Bring the system up in debug mode. Here it waits for a
kernel debugger connect; see ddb(4).
-q Boot the system in quiet mode.
-s Bring the system up in single-user mode.
-v Boot the system in verbose mode.
consdev dev
Immediately switch the console to the specified device dev and
reprint the banner. dev must be one of pc, com0, com1, com2,
com3, com0kbd, com1kbd, com2kbd, com3kbd, or auto. See Console
Selection Policy in boot_console(8).
dev [device]
Set the default drive and partition for subsequent filesystem
operations. Without an argument, print the current setting.
device is of the form specified in boot.
help Print an overview about commands and arguments.
ls [path]
Print a directory listing of path, containing inode number,
filename and file type. path can contain a device specifica-
tion.
quit Reboot the system.
In an emergency, the bootstrap methods described in the NetBSD installa-
tion notes for the i386 architecture can be used to boot from floppy.
FILES
/boot boot program code loaded by the primary boot-
strap
/netbsd system code
/netbsd.gz gzip-compressed system code
/usr/mdec/boot master copy of the boot program (copy to /boot)
/usr/mdec/bootxx_fstype primary bootstrap for filesystem type fstype,
copied to the start of the netbsd partition by
installboot(8).
SEE ALSO
ddb(4), userconf(4), boot_console(8), dosboot(8), halt(8),
installboot(8), mbr(8), pxeboot(8), reboot(8), shutdown(8), w95boot(8)
BUGS
This manual page documents the boot interface, which is used by ports
other than NetBSD/i386.
Any filename specified after the boot options, e.g.:
boot -d netbsd.test
is ignored, and the default kernel is booted.
Hard disks are always accessed by BIOS functions. Unit numbers are BIOS
device numbers which might differ from numbering in the NetBSD kernel or
physical parameters (e.g., SCSI slave numbers). There isn't any distinc-
tion between ``sd'' and ``wd'' devices at the bootloader level. This is
less a bug of the bootloader code than a shortcoming of the PC architec-
ture. The default disk device's name printed in the starting message is
derived from the ``type'' field of the NetBSD disklabel (if it is a hard
disk).
NetBSD 4.0 June 29, 2006 NetBSD 4.0
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