1.\" $NetBSD: boot.8,v 1.20 2019/09/16 01:57:58 manu Exp $ 2.\" 3.\" Copyright (c) 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software written and contributed 7.\" to Berkeley by William Jolitz. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94 34.\" 35.Dd September 13, 2019 36.Dt BOOT 8 x86 37.Os 38.Sh NAME 39.Nm boot 40.Nd 41system bootstrapping procedures 42.Sh DESCRIPTION 43Intel Architecture, 32-bit (IA-32) computers (the 44.Tn IBM PC 45and its clones) 46that can run 47.Nx Ns /i386 48or 49.Nx Ns /amd64 50can use any of the following boot procedures, depending on what the hardware and 51.Tn BIOS 52support: 53.Bl -tag -width "x86/pxeboot(8)" 54.It boot 55bootstrap 56.Nx 57from the system 58.Tn BIOS 59.It efiboot 60bootstrap 61.Nx 62from the system 63.Tn UEFI 64.It Xr x86/dosboot 8 65bootstrap 66.Nx 67from 68.Tn MS-DOS 69.It Xr x86/pxeboot 8 70network bootstrap 71.Nx 72from a 73.Tn TCP/IP 74.Tn LAN 75with 76.Tn DHCP , 77.Tn TFTP , 78and 79.Tn NFS . 80.El 81.Ss Power fail and crash recovery 82Normally, the system will reboot itself at power-up or after crashes. 83An automatic consistency check of the file systems will be performed, 84and unless this fails, the system will resume multi-user operations. 85.Ss Cold starts 86The 386 87.Tn "PC AT" 88clones attempt to boot the floppy disk drive A (otherwise known as drive 890) first, and failing that, attempt to boot the hard disk C (otherwise 90known as hard disk controller 1, drive 0). 91The 92.Nx 93bootblocks are loaded and started either by the 94.Tn BIOS , 95or by a boot selector program (such as OS-BS, BOOTEASY, the OS/2 Boot Menu or 96.Nx Ns 's 97.No boot-selecting 98master boot record - see 99.Xr x86/mbr 8 ) . 100.Ss Normal Operation 101Once running, a banner similar to the following will appear: 102.Bd -unfilled -offset indent 103>> NetBSD BIOS Boot, revision 3.0 104>> (user@buildhost, builddate) 105>> Memory: 637/15360 k 106Press return to boot now, any other key for boot menu 107booting hd0a:netbsd - starting in 5 108.Ed 109.Pp 110After a countdown, the system image listed will be loaded. 111In the example above, it will be 112.Dq Li hd0a:netbsd 113which is the file 114.Pa /netbsd 115on partition 116.Dq a 117of the 118.Nx 119.Tn MBR 120partition of the first hard disk known to the 121.Tn BIOS 122.Po 123which is an 124.Tn IDE 125or similar device - see the 126.Sx BUGS 127section 128.Pc . 129.Pp 130Pressing a key within the time limit, or before the boot program starts, will 131enter interactive mode. 132When using a short or 0 timeout, it is often useful to interrupt the boot 133by holding down a shift key, as some BIOSes and BIOS extensions will drain the 134keystroke buffer at various points during POST. 135.Pp 136If present, the file 137.Pa /boot.cfg 138will be used to configure the behaviour of the boot loader including 139setting the timeout, choosing a console device, altering the banner 140text and displaying a menu allowing boot commands to be easily chosen. 141See 142.Xr boot.cfg 5 . 143.Ss Boot Protocol 144The 145.Nx Ns /x86 146boot loader can boot a kernel using either the native 147.Nx 148boot protocol, or the 149.Dq multiboot 150protocol (which is compatible with some other operating systems). 151In the native 152.Nx 153boot protocol, options are passed from the boot loader 154to the kernel via flag bits in the 155.Va boothowto 156variable (see 157.Xr boothowto 9 ) . 158In the multiboot protocol, options are passed from the boot loader 159to the kernel as strings. 160.Ss Diagnostic Output 161If the first stage boot fails to load the boot, it will print a terse 162message indicating the reason for the failure. 163The possible error messages and their cause are listed in 164.Xr x86/mbr 8 . 165.Pp 166If the first stage boot succeeds, the banner will be shown and the 167error messages should be self-explanatory. 168.Ss Interactive mode 169In interactive mode, the boot loader will present a prompt, allowing 170input of these commands: 171.\" NOTE: much of this text is duplicated in the MI boot.8. 172.\" Some of it is 173.\" also duplicated in the x86-specific x86/dosboot.8 and x86/pxeboot.8; 174.\" please try to keep all relevant files synchronized. 175.Bl -tag -width 04n -offset 04n 176.It Ic boot Oo Va device : Oc Ns Oo Va filename Oc Oo Fl 1234abcdmqsvxz Oc 177The default 178.Va device 179will be set to the disk from which the boot loader was loaded. 180The partition is set to the first match in this list: 181.Bl -enum -compact 182.It 183The first 184.Xr gpt 8 185partition with the 186.Va bootme 187attribute set. 188.It 189The partition from which the boot loader was loaded from, if that 190can be detected. 191.It 192The first partition with a file system that could be bootable. 193.It 194The first partition. 195.El 196To boot from an alternate disk, the full name of the device should 197be given at the prompt. 198.Va device 199is of the form 200.Va NAME=partition_label 201when booting from a 202.Xr gpt 8 203partitioned disk. 204Otherwise, the syntax is 205.Xo Va xd 206.Op Va N Ns Op Va x 207.Xc 208where 209.Va xd 210is the device from which to boot, 211.Va N 212is the unit number, and 213.Va x 214is the partition letter. 215.Pp 216In the later case, the following list of supported devices may 217vary from installation to installation: 218.Pp 219.Bl -hang -compact 220.It hd 221Hard disks as numbered by the BIOS. 222This includes ST506, IDE, ESDI, RLL disks on a WD100[2367] or 223lookalike controller(s), and SCSI disks 224on SCSI controllers recognized by the BIOS. 225.It fd 226Floppy drives as numbered by the BIOS. 227.It cd 228CD-ROM drives as numbered by the BIOS. 229.It raid 230RAIDframe configured from hard disks recognized by the BIOS. 231Only RAID level 1 sets are supported by bootstrap code. 232If the RAID is partitioned, the first partition is used, or the 233first 234.Xr gpt 8 235partition that has the 236.Va bootme 237attribute set. 238Inner RAIDframe partitions can also be given to the 239.Ic dev 240command using he 241.Va NAME=partition_label 242syntax. 243.El 244.Pp 245The default 246.Va filename 247is 248.Pa netbsd ; 249if the boot loader fails to successfully 250open that image, it then tries 251.Pa netbsd.gz 252(expected to be a kernel image compressed by gzip), followed by 253.Pa onetbsd , 254.Pa onetbsd.gz , 255.Pa netbsd.old , 256and finally 257.Pa netbsd.old.gz . 258Alternate system images can be loaded by just specifying the name of the image. 259.Pp 260Options are: 261.Bl -tag -width xxx 262.It Fl 1 263Sets the machine-dependent flag 264.Sy RB_MD1 265in 266.Va boothowto . 267In 268.Nx Ns /x86 , 269this disables multiprocessor boot; 270the kernel will boot in uniprocessor mode. 271.It Fl 2 272Sets the machine-dependent flag 273.Sy RB_MD2 274in 275.Va boothowto . 276In 277.Nx Ns /x86 , 278this disables ACPI. 279.It Fl 3 280Sets the machine-dependent flag 281.Sy RB_MD3 282in 283.Va boothowto . 284In 285.Nx Ns /amd64 , 286this disables SVS. 287.It Fl 4 288Sets the machine-dependent flag 289.Sy RB_MD4 290in 291.Va boothowto . 292In 293.Nx Ns /x86 , 294this has no effect. 295.It Fl a 296Sets the 297.Sy RB_ASKNAME 298flag in 299.Va boothowto . 300This causes the kernel to prompt for the root file system device, 301the system crash dump device, and the path to 302.Xr init 8 . 303.It Fl b 304Sets the 305.Sy RB_HALT 306flag in 307.Va boothowto . 308This causes subsequent reboot attempts to halt instead of rebooting. 309.It Fl c 310Sets the 311.Sy RB_USERCONF 312flag in 313.Va boothowto . 314This causes the kernel to enter the 315.Xr userconf 4 316device configuration manager as soon as possible during the boot. 317.Xr userconf 4 318allows devices to be enabled or disabled, and allows device locators 319(such as hardware addresses or bus numbers) 320to be modified before the kernel attempts to attach the devices. 321.It Fl d 322Sets the 323.Sy RB_KDB 324flag in 325.Va boothowto . 326Requests the kernel to enter debug mode, in which it 327waits for a connection from a kernel debugger; see 328.Xr ddb 4 . 329.It Fl m 330Sets the 331.Sy RB_MINIROOT 332flag in 333.Va boothowto . 334Informs the kernel that a mini-root file system is present in memory. 335.It Fl q 336Sets the 337.Sy AB_QUIET 338flag in 339.Va boothowto . 340Boot the system in quiet mode. 341.It Fl s 342Sets the 343.Sy RB_SINGLE 344flag in 345.Va boothowto . 346Boot the system in single-user mode. 347.It Fl v 348Sets the 349.Sy AB_VERBOSE 350flag in 351.Va boothowto . 352Boot the system in verbose mode. 353.It Fl x 354Sets the 355.Sy AB_DEBUG 356flag in 357.Va boothowto . 358Boot the system with debug messages enabled. 359.It Fl z 360Sets the 361.Sy AB_SILENT 362flag in 363.Va boothowto . 364Boot the system in silent mode. 365.El 366.It Ic consdev Va dev 367Immediately switch the console to the specified device 368.Va dev 369and reprint the banner. 370.Va dev 371must be one of 372.\" .Bl -item -width com[0123]kbd -offset indent -compact 373.Ar pc , com0 , com1 , com2 , 374.Ar com3 , com0kbd , com1kbd , com2kbd , 375.Ar com3kbd , 376or 377.Ar auto . 378See 379.Sx Console Selection Policy 380in 381.Xr x86/boot_console 8 . 382.It Ic dev Op Va device 383Set the default drive and partition for subsequent file system 384operations. 385Without an argument, print the current setting. 386.Va device 387is of the form specified in 388.Cm boot . 389.It Ic fs Va file 390Load a file system image from the specified 391.Ar file , 392and request the kernel to use it as the root file system. 393The 394.Xr makefs 8 395utility may be used to create suitable file system images. 396.It Ic help 397Print an overview about commands and arguments. 398.It Ic load Va module Op Ar arguments 399Load the specified kernel 400.Va module , 401and pass it the specified 402.Ar arguments . 403If the module name is not an absolute path, 404.Pa /stand/ Xo Ns 405.Aq Sy arch Ns 406.Pa / Ns 407.Aq Sy osversion Ns 408.Pa /modules/ Ns 409.Aq Sy module Ns 410.Pa / Ns 411.Aq Sy module Ns 412.Pa .kmod 413.Xc 414is used. 415Possible uses of the 416.Ic load 417command include loading a memory disk image before booting a kernel, 418or loading a 419.Tn Xen 420DOM0 kernel before booting the 421.Tn Xen 422hypervisor. 423See 424.Xr boot.cfg 5 425for examples. 426.Pp 427In addition to the 428.Cm boot 429options specified above, the 430.Tn Xen 431DOM0 kernel accepts 432.Po Ar arguments 433being separated with spaces 434.Pc : 435.Bl -tag -width xxx 436.It Ic bootdev Ns = Ns Ar dev Po or Ic root Ns = Ns Ar dev Pc 437Override the default boot device. 438.Ar dev 439is of the form 440.Va NAME=partition_label 441for 442.Xr gpt 8 443partitioned disks. 444It can also be a unit name 445.Po Dq wd0 446.Pc , 447or an interface name 448.Po Dq bge0 , 449.Dq wm0 , 450\&... 451.Pc 452for cases where the root file system has to be loaded 453from network (see the 454.Sx BUGS 455section in 456.Xr x86/pxeboot 8 ) . 457.It Ic console Ns = Ns Ar dev 458Console used by DOM0 kernel during boot. 459.Ar dev 460accepts the same values as the ones given for the 461.Cm consdev 462command. 463See 464.Sx Console Selection Policy 465in 466.Xr x86/boot_console 8 . 467.It Xo Ic ip Ns = Ns 468.Ar my_ip : Ns Ar serv_ip : Ns Ar gw_ip : Ns 469.Ar mask : Ns Ar host : Ns Ar iface 470.Xc 471Specify various parameters for a network boot (IPs are in 472dot notation), 473each one separated by a colon: 474.Bl -tag -width xxxxxxx 475.It Va my_ip 476address of the host 477.It Va serv_ip 478address of the NFS server 479.It Va gw_ip 480address of the gateway 481.It Va mask 482network mask 483.It Va host 484address of the host 485.It Va iface 486interface 487.Po e.g., Dq xennet0 488or 489.Dq eth0 490.Pc 491.El 492.It Ic nfsroot Ns = Ns Ar address : Ns Ar rootpath 493Boot the system with root on NFS. 494.Ar address 495is the address of the NFS server, and 496.Ar rootpath 497is the remote mount point for the root file system. 498.It Ic pciback.hide Ns = Ns Ar pcidevs 499Pass a list of PCI IDs for use with the PCI backend driver, 500.Xr pciback 4 . 501.Ar pcidevs 502is formed of multiple IDs (in bus:device.function notation), 503each ID being surrounded with brackets. 504PCI domain IDs are currently ignored. 505See 506.Xr pciback 4 . 507.El 508.It Ic ls Op Pa path 509Print a directory listing of 510.Pa path , 511containing inode number, filename, and file type. 512.Pa path 513can contain a device specification. 514.It Ic menu 515Display the boot menu and initiate a countdown, 516similarly to what would have happened if interactive mode 517had not been entered. 518.It Ic modules Bro Ar on | off | enabled | disabled Brc 519The values 520.Ar enabled , on 521will enable module loading for 522.Cm boot 523and 524.Cm multiboot , 525whereas 526.Ar disabled , off 527will turn off the feature. 528.It Ic multiboot Va kernel Op Ar arguments 529Boot the specified 530.Va kernel , 531using the 532.Dq multiboot 533protocol instead of the native 534.Nx 535boot protocol. 536The 537.Va kernel 538is specified in the same way as with the 539.Ic boot 540command. 541.Pp 542The multiboot protocol may be used in the following cases: 543.Bl -tag -width indent 544.It Nx Ns / Ns Xen No kernels 545The 546.Tn Xen 547DOM0 kernel must be loaded as a module using the 548.Ic load 549command, and the 550.Tn Xen 551hypervisor must be booted using the 552.Ic multiboot 553command. 554Options for the DOM0 kernel (such as 555.Dq -s 556for single user mode) must be passed as options to the 557.Ic load 558command. 559Options for the hypervisor (such as 560.Dq dom0_mem=256M 561to reserve 256 MB of memory for DOM0) 562must be passed as options to the 563.Ic multiboot 564command. 565See 566.Xr boot.cfg 5 567for examples on how to boot 568.Nx Ns / Ns Xen. 569.It Nx No multiboot kernels 570A 571.Nx 572kernel that was built with 573.Cd options MULTIBOOT 574(see 575.Xr x86/multiboot 8 ) 576may be booted with either the 577.Ic boot 578or 579.Ic multiboot 580command, passing the same 581.Ar arguments 582in either case. 583.It Non- Ns Nx No kernels 584A kernel for a 585.No non- Ns Nx 586operating system that expects to be booted using the 587multiboot protocol (such as by the GNU 588.Dq GRUB 589boot loader) 590may be booted using the 591.Ic multiboot 592command. 593See the foreign operating system's documentation for the available 594.Ar arguments . 595.El 596.It Ic quit 597Reboot the system. 598.It Ic rndseed Ar file 599Load the specified 600.Ar file 601and request the kernel to use it as a seed for the 602.Xr rnd 4 603random number generator. 604The 605.Ar file 606should be in the private format used by 607.Xr rndctl 8 , 608and should have been saved by 609.Ql "rndctl -S" 610shortly before the previous shutdown. 611See the 612.Va random_seed 613and 614.Va random_file 615variables in 616.Xr rc.conf 5 , 617and the 618.Pa /etc/rc.d/random_seed 619script, for a way to manage the seed file. 620Using the same seed file on more then one host, 621or for more than one boot on the same host, 622will reduce the quality of random numbers 623and may impact system security. 624.It Ic userconf Va command 625Pass command 626.Va command 627to 628.Xr userconf 4 629at boot time. 630These commands are processed before the interactive 631.Xr userconf 4 632shell is executed, if requested. 633.It Ic splash Ar file 634Load a graphical image from the specified 635.Ar file 636and request the kernel to use it as a splash screen. 637The 638.Ar file 639should contain an image in one of these formats: 640JPEG (baseline only, not progressive), 641PNG (8-bit only), 642TGA, 643BMP (non-1bpp, non-RLE), 644GIF, 645PSD (composited view only), 646or 647PIC. 648.It Ic vesa Bro Va modenum | Ar on | off | enabled | disabled | list Brc 649Initialise the video card to the specified resolution and bit depth. 650The 651.Va modenum 652should be in the form of 653.Ar 0x100 , 800x600 , 800x600x32 . 654The values 655.Ar enabled , on 656put the display into the default mode, and 657.Ar disabled , off 658returns the display into standard vga mode. 659The value 660.Ar list 661lists all supported modes. 662.El 663.Pp 664In an emergency, the bootstrap methods described in the 665.Nx 666installation notes for the x86 architectures 667can be used to boot from floppy or other media, 668or over the network. 669.Ss Locating the root file system 670The kernel uses information from the bootloader to locate the 671file system to mount as root. 672There are three methods: 673.Bl -tag -width 04n -offset 04n 674.It Ic BTINFO_ROOTDEVICE Va from 675.Xr boot.cfg 5 676or multiboot. 677The bootloader passes the root device name as driver, unit, and 678partition (like sd0a). 679This will be automatically substituted by a 680.Xr dk 4 681wedge if one is discovered. 682.Pp 683The bootloader passes a wedge name as "wedge:" followed by the name. 684The kernel will search for a 685.Xr dk 4 686device with that name. 687.It Ic BTINFO_BOOTWEDGE Va determined by bootblock 688The bootloader passes start offset and length of a hard disk partition 689and a offset, size and hash of a "boot area". 690Then kernel searches 691all disks and wedges for a block sequence at that offset with a 692matching hash. 693If one is found, the kernel will look for a wedge 694on that device at the same offset. 695.Pp 696An additional partition number is provided if the bootloader also 697passed a BTINFO_BOOTDISK record. 698This (or partition 'a') will be used 699by the kernel as a fallback if there is no matching wedge. 700.It Ic BTINFO_BOOTDISK Va determined by bootblock 701This uses the device number passed by the BIOS that 702distinguishes between floppy, hard drive and CD-ROM boot. 703.Bl -tag -width xxx 704.It Ic Floppy 705The kernel searches for the 706.Xr fd 4 707device with the correct unit, the partition number is used 708to select a specific disk format. 709See 710.Xr fd 4 711for details. 712.It Ic Hard drive 713The bootloader passed a partition number and disklabel 714data (offset, type, checksum, packname). 715The kernel searches 716all disks for a matching disklabel. 717If one is found, the 718kernel will use that device and partition number. 719.It Ic CDROM 720The BIOS does not distinguish between multiple CD devices. 721The kernel searches for the first 722.Xr cd 4 723device. 724So you can only boot from unit 0. 725.El 726.El 727.Sh FILES 728.Bl -tag -width /usr/mdec/bootxx_fstype -compact 729.It Pa /boot 730boot program code loaded by the primary bootstrap 731.It Pa /boot.cfg 732optional configuration file 733.It Pa /netbsd 734system code 735.It Pa /netbsd.gz 736gzip-compressed system code 737.It Pa /usr/mdec/boot 738master copy of the boot program (copy to /boot) 739.It Pa /usr/mdec/bootxx_fstype 740primary bootstrap for file system type fstype, copied to the start of 741the 742.Nx 743partition by 744.Xr installboot 8 . 745.It Pa /usr/mdec/bootia32.efi 746.It Pa /usr/mdec/bootx64.efi 747.Tn UEFI 748bootstraps for 749.Nx Ns /i386 750and 751.Nx Ns /amd64 , 752which should be copied to the 753.Pa /efi/boot 754directory in a 755.Tn FAT 756formatted partition of type 757.Tn EFI 758(Either 759.Xr mbr 8 760and 761.Xr gpt 8 , 762see the 763.Sx BUGS 764section). 765.Nx 766.Tn UEFI 767bootstrap reads its configuration from the 768.Pa /efi/netBSD/boot.cfg 769file in the 770.Tn EFI 771partition. 772.El 773.Sh SEE ALSO 774.Xr ddb 4 , 775.Xr fd 4 , 776.Xr pciback 4 , 777.Xr userconf 4 , 778.Xr boot.cfg 5 , 779.Xr halt 8 , 780.Xr installboot 8 , 781.Xr reboot 8 , 782.Xr rescue 8 , 783.Xr shutdown 8 , 784.Xr x86/boot_console 8 , 785.Xr x86/dosboot 8 , 786.Xr x86/mbr 8 , 787.Xr x86/multiboot 8 , 788.Xr x86/pxeboot 8 , 789.Xr boothowto 9 790.Sh BUGS 791The kernel file name must be specified before, not after, the boot options. 792Any 793.Ar filename 794specified after the boot options, e.g.: 795.Pp 796.Bd -unfilled -offset indent -compact 797.Cm boot -d netbsd.test 798.Ed 799.Pp 800is ignored, and the default kernel is booted. 801.Pp 802Hard disks are always accessed by 803.Tn BIOS 804functions. 805Unit numbers are 806.Tn BIOS 807device numbers which might differ from numbering in the 808.Nx 809kernel or physical parameters 810.Po 811e.g., 812.Tn SCSI 813slave numbers 814.Pc . 815There isn't any distinction between 816.Dq sd 817and 818.Dq wd 819devices at the bootloader level. 820This is less a bug of the bootloader code than 821a shortcoming of the PC architecture. 822The default disk device's name printed in the starting message 823is derived from the 824.Dq type 825field of the 826.Nx 827disklabel (if it is a hard disk). 828.Pp 829.Tn UEFI 830implementation are supposed to support either 831.Xr mbr 8 832or 833.Xr gpt 8 834partitionning, but some do not handle the later. 835.Tn UEFI 836Booting 837from a 838.Xr gpt 8 839partitioned disk is still possible in this case, by adding 840an overlapping 841.Tn EFI 842partition in the protective 843.Xr mbr 8 844block. 845This can be achieved using the following commands 846(you must adapt the hard disk and 847.Tn EFI 848partition start end size to fit your setup): 849.Dl Ic dd if=/dev/rwd0d bs=512 count=1 of=mbr 850.Dl Ic fdisk -FIfaui1s 4/34/32768 -c /usr/mdec/mbr mbr 851.Dl Ic dd if=mbr bs=512 count=1 of=/dev/rwd0d conv=notrunc 852The resulting 853.Xr mbr 8 854partition table will look like this: 855.Bd -unfilled -offset indent 8560: GPT Protective MBR (sysid 238) 857 start 1, size 2097151 (1024 MB, Cyls 0-130/138/8) 858 PBR is not bootable: Bad magic number (0x0000) 8591: Primary DOS with 16 bit FAT <32M (sysid 4) 860 start 34, size 32768 (16 MB, Cyls 0/0/35-2/10/42), Active 8612: <UNUSED> 8623: <UNUSED> 863.Ed 864