boot
—
system bootstrapping procedures
This document provides information on using common features in the
NetBSD boot loader. Additional information may be
found in architecture-specific
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
boot.cfg(5).
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
installation 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.
Options are:
-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 system crash dump device, and the
path to init(8).
-b
- Sets the RB_HALT flag in
boothowto. This causes subsequent 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 manager 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 numbers) to be modified before the kernel
attempts to attach the devices.
-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 kernel that a mini-root
file system is present in memory.
-q
- Sets the AB_QUIET flag in
boothowto. Boot the system in quiet mode.
-s
- Sets the RB_SINGLE flag in
boothowto. Boot the system in single-user
mode.
-v
- Sets the AB_VERBOSE flag in
boothowto. Boot the system in verbose mode.
-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 silent 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
x86/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 specification.
quit
- Reboot the system.
In an emergency, the bootstrap methods described in the
NetBSD installation notes for the specific
architecture can be used.
- /boot
- boot program code loaded by the primary bootstrap
- /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).
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.:
is ignored, and the default kernel is booted.