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BOOT(8) NetBSD System Manager's Manual BOOT(8)
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boot -- system bootstrapping procedures
This document provides information on using common features in the NetBSD
boot loader. Additional information may be found in architecture-spe-
cific boot(8) manual pages.
In the native NetBSD boot protocol, options are passed from the boot
loader to the kernel via flag bits in the boothowto variable (see
boothowto(9)). Some boot loaders may also support other boot protocols.
Some boot loaders may present a menu, which may be configured via
In interactive mode, the boot loader will present a prompt, allowing
input of these commands:
boot [device:][filename] [-1234abcdmqsvxz]
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.
fd Floppy drives.
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.
-1 Sets the machine-dependent flag RB_MD1 in boothowto.
-2 Sets the machine-dependent flag RB_MD2 in boothowto.
-3 Sets the machine-dependent flag RB_MD3 in boothowto.
-4 Sets the machine-dependent flag RB_MD4 in boothowto.
-a Sets the RB_ASKNAME flag in boothowto. This causes the
kernel to prompt for the root file system device, the sys-
tem crash dump device, and the path to init(8).
-b Sets the RB_HALT flag in boothowto. This causes subse-
quent reboot attempts to halt instead of rebooting.
-c Sets the RB_USERCONF flag in boothowto. This causes the
kernel to enter the userconf(4) device configuration man-
ager as soon as possible during the boot. userconf(4)
allows devices to be enabled or disabled, and allows
device locators (such as hardware addresses or bus num-
bers) to be modified before the kernel attempts to attach
-d Sets the RB_KDB flag in boothowto. Requests the kernel to
enter debug mode, in which it waits for a connection from
a kernel debugger; see ddb(4).
-m Sets the RB_MINIROOT flag in boothowto. Informs the ker-
nel that a mini-root file system is present in memory.
-q Sets the AB_QUIET flag in boothowto. Boot the system in
-s Sets the RB_SINGLE flag in boothowto. Boot the system in
-v Sets the AB_VERBOSE flag in boothowto. Boot the system in
-x Sets the AB_DEBUG flag in boothowto. Boot the system with
debug messages enabled.
-z Sets the AB_SILENT flag in boothowto. Boot the system in
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 x86/boot_console(8).
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.
Print a directory listing of path, containing inode number,
filename, and file type. path can contain a device specifica-
quit Reboot the system.
In an emergency, the bootstrap methods described in the NetBSD installa-
tion notes for the specific architecture can be used.
/boot boot program code loaded by the primary boot-
/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
Architecture-specific boot(8) manual pages (such as emips/boot(8),
sparc64/boot(8), x86/boot(8)), ddb(4), userconf(4), halt(8),
installboot(8), reboot(8), rescue(8), shutdown(8), boothowto(9)
The kernel file name must be specified before, not after, the boot
options. Any filename specified after the boot options, e.g.:
boot -d netbsd.test
is ignored, and the default kernel is booted.
NetBSD 10.99 August 16, 2014 NetBSD 10.99