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BOOT(8)		       BSD/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 partition
     "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 of-
     ten 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.

     If	present, the file /boot.cfg will be used to configure the behaviour of
     the boot loader including setting the timeout, choosing a console device,
     altering the banner text and displaying a menu allowing boot commands to
     be	easily chosen.	See boot.cfg(5).

     The NetBSD/i386 boot loader can boot a kernel using either	the native
     NetBSD boot protocol, or the "multiboot" protocol (which is compatible
     with some other operating systems).  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)).	 In the	multiboot protocol,
     options are passed	from the boot loader to	the kernel as strings.

   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 in-
     put 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 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:

	       -1   Sets the machine-dependent flag RB_MD1 in boothowto.  In
		    NetBSD/i386, this disables multiprocessor boot; the	kernel
		    will boot in uniprocessor mode.

	       -2   Sets the machine-dependent flag RB_MD2 in boothowto.  In
		    NetBSD/i386, this disables ACPI.

	       -3   Sets the machine-dependent flag RB_MD3 in boothowto.  In
		    NetBSD/i386, this has no effect.

	       -4   Sets the machine-dependent flag RB_MD4 in boothowto.  In
		    NetBSD/i386, this has no effect.

	       -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) al-
		    lows 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 ker-
		    nel	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 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.

	 load module [arguments]
	       Load the	specified kernel module, and pass it the specified
	       arguments.  If the module name is not an	absolute path, /stand/
	       <arch>/<osversion>/modules/<module>/<module>.kmod is used.
	       Possible	used of	the load command include loading a memory disk
	       image before booting a kernel, or loading a Xen DOM0 kernel be-
	       fore booting the	Xen hypervisor.	 See boot.cfg(5) for examples.

	       In addition to the boot options specified above,	the DOM0 ker-
	       nel accepts (arguments being separated with spaces):

	       bootdev=dev (or root=dev)
		    Override the default boot device.  dev can be a unit name
		    ("wd0"), or	an interface name ("bge0", "wm0", ...),	for
		    cases where	the root file system has to be loaded from
		    network (see the BUGS section in pxeboot(8)).

	       console=dev
		    Console used by DOM0 kernel	during boot.  dev accepts the
		    same values	as the ones given for the consdev command.
		    See	Console	Selection Policy in boot_console(8).

	       ip=my_ip:serv_ip:gw_ip:mask:host:iface
		    Specify various parameters for a network boot (IPs are in
		    dot	notation), each	one separated by a colon:

		    my_ip    address of	the host

		    serv_ip  address of	the NFS	server

		    gw_ip    address of	the gateway

		    mask     network mask

		    host     address of	the host

		    iface    interface (e.g. "xennet0" or "eth0")

	       nfsroot=address:rootpath
		    Boot the system with root on NFS.  address is the address
		    of the NFS server, and rootpath is the remote mount	point
		    for	the root file system.

	       pciback.hide=pcidevs
		    Pass a list	of PCI IDs for use with	the PCI	backend
		    driver, pciback(4).	 pcidevs is formed of multiple IDs (in
		    bus:device.function	notation), each	ID being surrounded
		    with brackets.  PCI	domain IDs are currently ignored.  See
		    pciback(4).

	 ls [path]
	       Print a directory listing of path, containing inode number,
	       filename, and file type.	 path can contain a device specifica-
	       tion.

	 modules {on | off | enabled | disabled}
	       The values enabled, on will enable module loading for boot and
	       multiboot, whereas disabled, off	will turn off the feature.

	 multiboot kernel [arguments]
	       Boot the	specified kernel, using	the "multiboot"	protocol in-
	       stead of	the native NetBSD boot protocol.  The kernel is	speci-
	       fied in the same	way as with the	boot command.

	       The multiboot protocol may be used in the following cases:

	       NetBSD/Xen kernels
		       The Xen DOM0 kernel must	be loaded as a module using
		       the load	command, and the Xen hypervisor	must be	booted
		       using the multiboot command.  Options for the DOM0 ker-
		       nel (such as "-s" for single user mode) must be passed
		       as options to the load command.	Options	for the	hyper-
		       visor (such as "dom0_mem=256M" to reserve 256 MB	of
		       memory for DOM0)	must be	passed as options to the
		       multiboot command.  See boot.cfg(5) for examples	on how
		       to boot NetBSD/Xen.

	       NetBSD multiboot	kernels
		       A NetBSD	kernel that was	built with options MULTIBOOT
		       (see multiboot(8)) may be booted	with either the	boot
		       or multiboot command, passing the same arguments	in ei-
		       ther case.

	       Non-NetBSD kernels
		       A kernel	for a non-NetBSD operating system that expects
		       to be booted using the multiboot	protocol (such as by
		       the GNU "GRUB" boot loader) may be booted using the
		       multiboot command.  See the foreign operating system's
		       documentation for the available arguments.

	 quit  Reboot the system.

	 userconf command
	       Pass the	command	to userconf(4) at boot time .  These commands
	       are processed before the	interactive userconf(4)	shell is exe-
	       cuted, if requested .

	 vesa {modenum | on | off | enabled | disabled | list}
	       Initialise the video card to the	specified resolution and bit
	       depth.  The modenum should be in	the form of 0x100, 800x600,
	       800x600x32.  The	values enabled,	on put the display into	the
	       default mode, and disabled, off returns the display into	stan-
	       dard vga	mode.  The value list lists all	supported modes.

     In	an emergency, the bootstrap methods described in the NetBSD installa-
     tion notes	for the	i386 architecture can be used to boot from floppy or
     other media, or over the network.

FILES
     /boot		      boot program code	loaded by the primary boot-
			      strap
     /boot.cfg		      optional configuration file
     /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), pciback(4), userconf(4), boot.cfg(5), boot_console(8),
     dosboot(8), halt(8), installboot(8), mbr(8), multiboot(8),	pxeboot(8),
     reboot(8),	shutdown(8), w95boot(8), boothowto(9)

BUGS
     The kernel	file name must be specified before, not	after, the boot	op-
     tions.  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 architecture.
     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).

BSD				 May 26, 2011				   BSD

NAME | DESCRIPTION | FILES | SEE ALSO | BUGS

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