1.\" Copyright (c) 1987, 1988, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Symmetric Computer Systems. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgment: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94 36.\" $FreeBSD: src/sbin/disklabel/disklabel.8,v 1.15.2.22 2003/04/17 17:56:34 trhodes Exp $ 37.\" $DragonFly: src/sbin/disklabel/disklabel.8,v 1.30 2008/09/16 20:45:36 thomas Exp $ 38.\" 39.Dd September 28, 2009 40.Dt DISKLABEL32 8 41.Os 42.Sh NAME 43.Nm disklabel32 44.Nd read and write 32 bit disk pack label 45.Sh SYNOPSIS 46.Nm 47.Op Fl r 48.Ar disk 49.Nm 50.Fl w 51.Op Fl r 52.Op Fl n 53.Ar disk Ar disktype Ns / Ns Cm auto 54.Oo Ar packid Oc 55.Nm 56.Fl e 57.Op Fl r 58.Op Fl n 59.Ar disk 60.Nm 61.Fl R 62.Op Fl r 63.Op Fl n 64.Ar disk Ar protofile 65.Nm 66.Op Fl NW 67.Ar disk 68.Pp 69.Nm 70.Fl B 71.Oo 72.Fl b Ar boot1 73.Fl s Ar boot2 74.Oc 75.Ar disk 76.Oo Ar disktype Ns / Ns Cm auto Oc 77.Nm 78.Fl w 79.Fl B 80.Op Fl n 81.Oo 82.Fl b Ar boot1 83.Fl s Ar boot2 84.Oc 85.Ar disk Ar disktype Ns / Ns Cm auto 86.Oo Ar packid Oc 87.Nm 88.Fl R 89.Fl B 90.Op Fl n 91.Oo 92.Fl b Ar boot1 93.Fl s Ar boot2 94.Oc 95.Ar disk Ar protofile 96.Oo Ar disktype Ns / Ns Cm auto Oc 97.Nm 98.Fl f Ar slice_start_lba 99.Oo Ar options Oc 100.Sh DESCRIPTION 101The 102.Nm 103utility 104installs, examines or modifies a 32 bit label on a disk drive or pack. 105When writing 106the label, it can be used to change the drive identification, the disk 107partitions on the drive, or to replace a damaged label. 108There are several forms 109of the command that read (display), install or edit the label on a disk. 110In 111addition, 112.Nm 113can install bootstrap code. 114.Ss Raw or in-core label 115The disk label resides close to or at the beginning of each disk slice. 116For faster access, the kernel maintains a copy in core at all times. 117By 118default, most forms of the 119.Nm 120command access the in-core copy of the label. 121To access the raw (on-disk) 122copy, use the 123.Fl r 124option. 125This option allows a label to be installed on a disk without kernel 126support for a label, such as when labels are first installed on a system; it 127must be used when first installing a label on a disk. 128The specific effect of 129.Fl r 130is described under each command. 131.Ss Disk device name 132All 133.Nm 134forms require a disk device name, which should always be the raw 135device name representing the disk or slice. 136.Dx 137uses the following scheme for slice numbering: 138If the disk doesn't use GPT (typically laid out by 139.Xr gpt 8 ) , 140but e.g.\& MBR (typically laid out by 141.Xr fdisk 8 ) , 142then slice 0, e.g.\& 143.Pa da0s0 , 144represents the entire disk regardless of any DOS partitioning. 145Slice 0 is called the compatibility slice, 146and slice 1 and onward, e.g.\& 147.Pa da0s1 , 148represents a 149.Bx 150slice. 151If the disk does use GPT, then all slices are 152.Bx 153slices, slice 0 isn't special, it is just the first slice on the disk. 154You do not have to include the 155.Pa /dev/ 156path prefix when specifying the device. 157The 158.Nm 159utility will automatically prepend it. 160.Ss Reading the disk label 161To examine the label on a disk drive, use 162.Nm 163without options: 164.Pp 165.Nm 166.Op Fl r 167.Ar disk 168.Pp 169.Ar disk 170represents the raw disk in question, and may be in the form 171.Pa da0s1 172or 173.Pa /dev/da0s1 . 174It will display all of the parameters associated with the drive and its 175partition layout. 176Unless the 177.Fl r 178flag is given, 179the kernel's in-core copy of the label is displayed; 180if the disk has no label, or the partition types on the disk are incorrect, 181the kernel may have constructed or modified the label. 182If the 183.Fl r 184flag is given, 185.Nm 186reads the label from the raw disk and displays it. 187Both versions are usually 188identical except in the case where a label has not yet been initialized or 189is corrupt. 190.Ss Writing a standard label 191To write a standard label, use the form 192.Pp 193.Nm 194.Fl w 195.Op Fl r 196.Op Fl n 197.Ar disk Ar disktype Ns / Ns Cm auto 198.Oo Ar packid Oc 199.Pp 200The required arguments to 201.Nm 202are the drive to be labeled and the drive type as described in the 203.Xr disktab 5 204file. 205The drive parameters and partitions are taken from that file. 206If 207different disks of the same physical type are to have different partitions, it 208will be necessary to have separate disktab entries describing each, or to edit 209the label after installation as described below. 210The optional argument is a 211pack identification string, up to 16 characters long. 212The pack id must be 213quoted if it contains blanks. 214.Pp 215If the 216.Fl n 217flag is given, no data will be written to the device, and instead the 218disklabel that would have been written will be printed to stdout. 219.Pp 220If the 221.Fl r 222flag is given, the disk sectors containing the label and bootstrap 223will be written directly. 224A side-effect of this is that any existing bootstrap code will be overwritten 225and the disk rendered unbootable. 226See the boot options below for a method of 227writing the label and the bootstrap at the same time. 228If 229.Fl r 230is not specified, 231the existing label will be updated via the in-core copy and any bootstrap 232code will be unaffected. 233If the disk does not already have a label, the 234.Fl r 235flag must be used. 236In either case, the kernel's in-core label is replaced. 237.Pp 238For a virgin disk that is not known to 239.Xr disktab 5 , 240.Ar disktype 241can be specified as 242.Cm auto . 243In this case, the driver is requested to produce a virgin label for the 244disk. 245This might or might not be successful, depending on whether the 246driver for the disk is able to get the required data without reading 247anything from the disk at all. 248It will likely succeed for all SCSI 249disks, most IDE disks, and vnode devices. 250Writing a label to the 251disk is the only supported operation, and the 252.Ar disk 253itself must be provided as the canonical name, i.e.\& not as a full 254path name. 255.Pp 256For most harddisks, a label based on percentages for most partitions (and 257one partition with a size of 258.Ql * ) 259will produce a reasonable configuration. 260.Pp 261PC-based systems have special requirements in order for the BIOS to properly 262recognize a 263.Dx 264disklabel. 265Older systems may require what is known as a 266.Dq dangerously dedicated 267disklabel, which creates a fake DOS partition to work around problems older 268BIOSes have with modern disk geometries. 269On newer systems you generally want 270to create a normal DOS partition using 271.Ar fdisk 272and then create a 273.Dx 274disklabel within that slice. 275This is described 276later on in this page. 277.Pp 278Installing a new disklabel does not in of itself allow your system to boot 279a kernel using that label. 280You must also install boot blocks, which is 281described later on in this manual page. 282.Ss Editing an existing disk label 283To edit an existing disk label, use the form 284.Pp 285.Nm 286.Fl e 287.Op Fl r 288.Op Fl n 289.Ar disk 290.Pp 291This command reads the label from the in-core kernel copy, or directly from the 292disk if the 293.Fl r 294flag is also specified. 295The label is written to a file in ASCII and then 296supplied to an editor for changes. 297If no editor is specified in an 298.Ev EDITOR 299environment variable, 300.Xr vi 1 301is used. 302When the editor terminates, the label file is used to rewrite the disk label. 303Existing bootstrap code is unchanged regardless of whether 304.Fl r 305was specified. 306If 307.Fl n 308is specified, no data will be written to the device, and instead the 309disklabel that would have been written will be printed to stdout. 310This is 311useful to see how a partitioning scheme will work out for a specific disk. 312.Ss Restoring a disk label from a file 313To restore a disk label from a file, use the form 314.Pp 315.Nm 316.Fl R 317.Op Fl r 318.Op Fl n 319.Ar disk Ar protofile 320.Pp 321.Nm 322is capable of restoring a disk label that was previously saved in a file 323in ASCII format. 324The prototype file used to create the label should be in the same format 325as that produced when reading or editing a label. 326Comments are delimited by 327.Ql # 328and newline. 329As when writing a new label, any existing bootstrap code will be 330clobbered if 331.Fl r 332is specified and will be unaffected otherwise. 333See the boot options below for a 334method of restoring the label and writing the bootstrap at the same time. 335If 336.Fl n 337is used, no data will be written to the device, and instead the 338disklabel that would have been written will be printed to stdout. 339This is 340useful to see how a partitioning scheme will work out for a specific disk. 341.Ss Enabling and disabling writing to the disk label area 342By default, it is not possible to write to the disk label area at the beginning 343of a disk. 344The disk driver arranges for 345.Xr write 2 346and similar system calls 347to return 348.Er EROFS 349on any attempt to do so. 350If you need 351to write to this area (for example, to obliterate the label), use the form 352.Pp 353.Nm 354.Fl W 355.Ar disk 356.Pp 357To disallow writing to the label area after previously allowing it, 358use the command 359.Pp 360.Nm 361.Fl N 362.Ar disk 363.Ss Installing bootstraps 364The final three forms of 365.Nm 366are used to install bootstrap code, which allows boot from a 367.Xr UFS 5 368file system. 369If you are creating a 370.Dq dangerously-dedicated 371slice for compatibility with older PC systems, 372you generally want to specify the compatibility slice, such as 373.Pa da0s0 . 374If you are creating a label within an existing DOS slice, 375you should specify 376the slice name such as 377.Pa da0s1 . 378Making a slice bootable can be tricky. 379If you are using a normal DOS 380slice you typically install (or leave) a standard MBR on the base disk and 381then install the 382.Dx 383bootblocks in the slice. 384.Pp 385.Nm 386.Fl B 387.Oo 388.Fl b Ar boot1 389.Fl s Ar boot2 390.Oc 391.Ar disk 392.Oo Ar disktype Ns / Ns Cm auto Oc 393.Pp 394This form installs the bootstrap only. 395It does not change the disk label. 396You should never use this command on the compatibility slice unless you 397intend to create a 398.Dq dangerously-dedicated 399disk, such as 400.Ar da0s0 . 401This command is typically run on a 402.Bx 403slice such as 404.Ar da0s1 . 405.Pp 406.Nm 407.Fl w 408.Fl B 409.Op Fl n 410.Oo 411.Fl b Ar boot1 412.Fl s Ar boot2 413.Oc 414.Ar disk Ar disktype Ns / Ns Cm auto 415.Oo Ar packid Oc 416.Pp 417This form corresponds to the 418.Dq write label 419command described above. 420In addition to writing a new volume label, it also installs the bootstrap. 421If run on the compatibility slice this command will create a 422.Dq dangerously-dedicated 423label. 424This command is normally run on a 425.Bx 426slice rather than the compatibility slice. 427If 428.Fl n 429is used, no data will be written to the device, and instead the 430disklabel that would have been written will be printed to stdout. 431.Pp 432.Nm 433.Fl R 434.Fl B 435.Op Fl n 436.Oo 437.Fl b Ar boot1 438.Fl s Ar boot2 439.Oc 440.Ar disk Ar protofile 441.Oo Ar disktype Ns / Ns Cm auto Oc 442.Pp 443This form corresponds to the 444.Dq restore label 445command described above. 446In addition to restoring the volume label, it also installs the bootstrap. 447If run on the compatibility slice this command will create a 448.Dq dangerously-dedicated 449label. 450This command is normally run on a 451.Bx 452slice rather than the compatibility 453slice. 454.Pp 455The bootstrap commands always access the disk directly, 456so it is not necessary to specify the 457.Fl r 458flag. 459If 460.Fl n 461is used, no data will be written to the device, and instead the 462disklabel that would have been written will be printed to stdout. 463.Pp 464The bootstrap code is comprised of two boot programs. 465Specify the name of the 466boot programs to be installed in one of these ways: 467.Bl -enum 468.It 469Specify the names explicitly with the 470.Fl b 471and 472.Fl s 473flags. 474.Fl b 475indicates the primary boot program and 476.Fl s 477the secondary boot program. 478The boot programs are normally located in 479.Pa /boot . 480.It 481If the 482.Fl b 483and 484.Fl s 485flags are not specified, but 486.Ar disktype 487was specified, the names of the programs are taken from the 488.Dq b0 489and 490.Dq b1 491parameters of the 492.Xr disktab 5 493entry for the disk if the disktab entry exists and includes those parameters. 494.It 495Otherwise, the default boot image names are used: 496.Pa /boot/boot1 497and 498.Pa /boot/boot2 499for the standard stage1 and stage2 boot images. 500.El 501.Ss Initializing/Formatting a bootable disk from scratch 502To initialize a disk from scratch the following sequence is recommended. 503Please note that this will wipe everything that was previously on the disk, 504including any 505.No non- Ns Dx 506slices. 507.Bl -enum 508.It 509Use 510.Xr gpt 8 511or 512.Xr fdisk 8 513to initialize the hard disk, and create a GPT or MBR slice table, 514referred to as the 515.Dq "partition table" 516in 517.Tn DOS . 518.It 519Use 520.Nm 521or 522.Xr disklabel64 8 523to define partitions on 524.Dx 525slices created in the previous step. 526.It 527Finally use 528.Xr newfs_hammer 8 529or 530.Xr newfs 8 531to create file systems on new partitions. 532.El 533.Pp 534A typical partitioning scheme would be to have an 535.Ql a 536partition 537of approximately 512MB to hold the root file system, a 538.Ql b 539partition for 540swap (usually 4GB), a 541.Ql d 542partition for 543.Pa /var 544(usually 2GB), an 545.Ql e 546partition for 547.Pa /var/tmp 548(usually 2GB), an 549.Ql f 550partition for 551.Pa /usr 552(usually around 4GB), 553and finally a 554.Ql g 555partition for 556.Pa /home 557(usually all remaining space). 558If you are tight on space all sizes can be halved. 559Your mileage may vary. 560.Pp 561.Dl "fdisk -BI da0" 562.Dl "disklabel32 -w -B da0s1 auto" 563.Dl "disklabel32 -e da0s1" 564.Ss Manual offset 565.Dx 566no longer snoop-adjusts the on-disk label when reading or writing 567raw labels. 568.Nm 569is now responsible for adjusting the label when operating in raw mode. 570Traditional (32 bit, 571.Bx ) 572disklabels store offsets as absolute block numbers 573rather than slice-relative block numbers. 574If 575.Nm 576is unable to issue the 577.Dv DIOCGPART 578ioctl to get slice information it will 579refuse to read or write the label in raw mode. 580The 581.Fl f 582option may be used to force the operation by supplying a manual offset. 583.Sh FILES 584.Bl -tag -width ".Pa /etc/disktab" -compact 585.It Pa /boot/boot1 586Default stage1 boot image. 587.It Pa /boot/boot2 588Default stage2 boot image. 589.It Pa /etc/disktab 590Disk description file. 591.El 592.Sh SAVED FILE FORMAT 593The 594.Nm 595utility uses an 596.Tn ASCII 597version of the label when examining, editing, or restoring a disk label. 598The format is: 599.Bd -literal -offset 4n 600# /dev/ad4s4: 601type: unknown 602disk: amnesiac 603label: fictitious 604flags: 605bytes/sector: 512 606sectors/track: 63 607tracks/cylinder: 24 608sectors/cylinder: 1512 609cylinders: 161098 610sectors/unit: 243581184 611rpm: 3600 612interleave: 1 613trackskew: 0 614cylinderskew: 0 615headswitch: 0 # milliseconds 616track-to-track seek: 0 # milliseconds 617drivedata: 0 618 61916 partitions: 620# size offset fstype 621 a: 1048560 16 4.2BSD # 511.992MB 622 b: 8388608 1048576 swap # 4096.000MB 623 c: 243581184 0 unused # 118936.125MB 624 d: 4194304 9437184 4.2BSD # 2048.000MB 625 e: 4194304 13631488 4.2BSD # 2048.000MB 626 f: 8388608 17825792 4.2BSD # 4096.000MB 627 h: 196395264 26214400 HAMMER # 95896.125MB 628 i: 10485760 222609664 ccd # 5120.000MB 629 j: 10485760 233095424 vinum # 5120.000MB 630.Ed 631.Pp 632Lines starting with a 633.Ql # 634mark are comments. 635Most of the other specifications are no longer used. 636The ones which must still be set correctly are: 637.Bl -inset 638.It Ar label 639is an optional label, set by the 640.Ar packid 641option when writing a label. 642.It Ar flags 643may be 644.Cm removable , ecc 645or 646.Cm badsect . 647.Cm removable 648is set for removable media drives, but no current 649.Dx 650driver evaluates this 651flag. 652.Cm ecc 653is no longer supported; 654.Cm badsect 655specifies that the drive can perform bad sector remapping. 656.It Ar sectors/unit 657describes the total size of the disk. 658This value must be correct. 659.It Ar "the partition table" 660is the 661.Ux 662partition table, not the 663.Tn DOS 664partition table described in 665.Xr fdisk 8 . 666.El 667.Pp 668The partition table can have up to 16 entries. 669It contains the following information: 670.Bl -tag -width indent 671.It Ar # 672The partition identifier is a single letter in the range 673.Ql a 674to 675.Ql p . 676By convention, partition 677.Ql c 678is reserved to describe the entire disk. 679.It Ar size 680The size of the partition in sectors, 681.Cm K 682(kilobytes - 1024), 683.Cm M 684(megabytes - 1024*1024), 685.Cm G 686(gigabytes - 1024*1024*1024), 687.Cm % 688(percentage of free space 689.Em after 690removing any fixed-size partitions other than partition 691.Ql c ) , 692or 693.Cm * 694(all remaining free space 695.Em after 696fixed-size and percentage partitions). 697For partition 698.Ql c , 699a size of 700.Cm * 701indicates the entire disk. 702Lowercase versions of 703.Cm K , M , 704and 705.Cm G 706are allowed. 707Size and type should be specified without any spaces between them. 708.Pp 709Example: 2097152, 1G, 1024M and 1048576K are all the same size 710(assuming 512-byte sectors). 711.It Ar offset 712The offset of the start of the partition from the beginning of the 713drive in sectors, or 714.Cm * 715to have 716.Nm 717calculate the correct offset to use (the end of the previous partition plus 718one, ignoring partition 719.Ql c . 720For partition 721.Ql c , 722.Cm * 723will be interpreted as an offset of 0. 724.It Ar fstype 725Describes the purpose of the partition. 726The example shows all currently used partition types. 727For 728.Xr UFS 5 729file systems, use type 730.Cm 4.2BSD . 731For 732.Xr HAMMER 5 733file systems, use type 734.Cm HAMMER . 735For 736.Xr ccd 4 737partitions, use type 738.Cm ccd . 739For Vinum drives, use type 740.Cm vinum . 741Other common types are 742.Cm swap 743and 744.Cm unused . 745By convention, partition 746.Ql c 747represents the entire slice and should be of type 748.Cm unused , 749though 750.Nm 751does not enforce this convention. 752The 753.Nm 754utility 755also knows about a number of other partition types, 756none of which are in current use. 757(See 758.Dv fstypenames 759in 760.In sys/dtype.h 761for more details). 762.El 763.Pp 764The remainder of the line is a comment and shows the size of 765the partition in MB. 766.Sh EXAMPLES 767.Dl "disklabel32 da0s1" 768.Pp 769Display the in-core label for the first slice of the 770.Pa da0 771disk, as obtained via 772.Pa /dev/da0s1 . 773(If the disk is 774.Dq dangerously-dedicated , 775the compatibility slice name should be specified, such as 776.Pa da0s0 . ) 777.Pp 778.Dl "disklabel32 da0s1 > savedlabel" 779.Pp 780Save the in-core label for 781.Pa da0s1 782into the file 783.Pa savedlabel . 784This file can be used with the 785.Fl R 786option to restore the label at a later date. 787.Pp 788.Dl "disklabel32 -w -r /dev/da0s1 da2212 foo" 789.Pp 790Create a label for 791.Pa da0s1 792based on information for 793.Dq da2212 794found in 795.Pa /etc/disktab . 796Any existing bootstrap code will be clobbered 797and the disk rendered unbootable. 798.Pp 799.Dl "disklabel32 -e -r da0s1" 800.Pp 801Read the on-disk label for 802.Pa da0s1 , 803edit it, and reinstall in-core as well as on-disk. 804Existing bootstrap code is unaffected. 805.Pp 806.Dl "disklabel32 -e -r -n da0s1" 807.Pp 808Read the on-disk label for 809.Pa da0s1 , 810edit it, and display what the new label would be (in sectors). 811It does 812.Em not 813install the new label either in-core or on-disk. 814.Pp 815.Dl "disklabel32 -r -w da0s1 auto" 816.Pp 817Try to auto-detect the required information from 818.Pa da0s1 , 819and write a new label to the disk. 820Use another 821.Nm Fl e 822command to edit the 823partitioning and file system information. 824.Pp 825.Dl "disklabel32 -R da0s1 savedlabel" 826.Pp 827Restore the on-disk and in-core label for 828.Pa da0s1 829from information in 830.Pa savedlabel . 831Existing bootstrap code is unaffected. 832.Pp 833.Dl "disklabel32 -R -n da0s1 label_layout" 834.Pp 835Display what the label would be for 836.Pa da0s1 837using the partition layout in 838.Pa label_layout . 839This is useful for determining how much space would be allotted for various 840partitions with a labelling scheme using 841.Cm % Ns -based 842or 843.Cm * 844partition sizes. 845.Pp 846.Dl "disklabel32 -B da0s1" 847.Pp 848Install a new bootstrap on 849.Pa da0s1 . 850The boot code comes from 851.Pa /boot/boot1 852and possibly 853.Pa /boot/boot2 . 854On-disk and in-core labels are unchanged. 855.Pp 856.Dl "disklabel32 -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212" 857.Pp 858Install a new label and bootstrap. 859The label is derived from disktab information for 860.Dq da2212 861and installed both in-core and on-disk. 862The bootstrap code comes from the files 863.Pa newboot1 864and 865.Pa newboot2 . 866.Pp 867.Dl "dd if=/dev/zero of=/dev/da0 bs=512 count=32" 868.Dl "fdisk -BI da0" 869.Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32" 870.Dl "disklabel32 -w -B da0s1 auto" 871.Dl "disklabel32 -e da0s1" 872.Pp 873Completely wipe any prior information on the disk, creating a new bootable 874disk with a DOS partition table containing one 875.Dq whole-disk 876slice. 877Then 878initialize the slice, then edit it to your needs. 879The 880.Pa dd 881commands are optional, but may be necessary for some BIOSes to properly 882recognize the disk. 883.Pp 884.Dl "disklabel32 -W da0s1" 885.Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32" 886.Dl "disklabel64 -r -w da0s1 auto" 887.Dl "disklabel64 -N da0s1" 888.Pp 889Completely wipe any prior information on the slice, 890changing label format to 64 bit. 891The wiping is needed as 892.Nm disklabel64 893and 894.Nm , 895as a safety measure, 896won't do any operations if label with other format is already installed. 897.Pp 898This is an example disklabel that uses some of the new partition size types 899such as 900.Cm % , M , G , 901and 902.Cm * , 903which could be used as a source file for 904.Pp 905.Dl "disklabel32 -R ad0s1 new_label_file" 906.Bd -literal -offset 4n 907# /dev/ad0s1: 908type: ESDI 909disk: ad0s1 910label: 911flags: 912bytes/sector: 512 913sectors/track: 63 914tracks/cylinder: 16 915sectors/cylinder: 1008 916cylinders: 40633 917sectors/unit: 40959009 918rpm: 3600 919interleave: 1 920trackskew: 0 921cylinderskew: 0 922headswitch: 0 # milliseconds 923track-to-track seek: 0 # milliseconds 924drivedata: 0 925 92616 partitions: 927# size offset fstype 928 a: 400M 0 4.2BSD 929 b: 1G * swap 930 c: * * unused 931 e: 204800 * 4.2BSD 932 f: 5g * 4.2BSD 933 g: * * 4.2BSD 934.Ed 935.Sh DIAGNOSTICS 936The kernel device drivers will not allow the size of a disk partition 937to be decreased or the offset of a partition to be changed while it is open. 938Some device drivers create a label containing only a single large partition 939if a disk is unlabeled; thus, the label must be written to the 940.Ql a 941partition of the disk while it is open. 942This sometimes requires the desired 943label to be set in two steps, the first one creating at least one other 944partition, and the second setting the label on the new partition while 945shrinking the 946.Ql a 947partition. 948.Pp 949On some machines the bootstrap code may not fit entirely in the area 950allocated for it by some file systems. 951As a result, it may not be possible to have file systems on some partitions 952of a 953.Dq bootable 954disk. 955When installing bootstrap code, 956.Nm 957checks for these cases. 958If the installed boot code would overlap a partition of type 959.Dv FS_UNUSED 960it is marked as type 961.Dv FS_BOOT . 962The 963.Xr newfs 8 964utility will disallow creation of file systems on 965.Dv FS_BOOT 966partitions. 967Conversely, if a partition has a type other than 968.Dv FS_UNUSED 969or 970.Dv FS_BOOT , 971.Nm 972will not install bootstrap code that overlaps it. 973.Sh COMPATIBILITY 974Due to 975.Xr disklabel32 5 976storing sector numbers in 32 bit format 977.Nm 978is restricted to 2TB, using the prevalent sector size of 512B. 979.Xr disklabel64 5 980labels should be used to partition larger disks. 981.Pp 982The various 983.Bx Ns s 984use slightly different versions of 985.Bx 986disklabels 987and are not generally compatible. 988The 989.Dx 990kernel can often use labels from other 991.Bx Ns s 992for read-only operation. 993.Sh SEE ALSO 994.Xr dd 1 , 995.Xr ccd 4 , 996.Xr disklabel32 5 , 997.Xr disktab 5 , 998.Xr boot0cfg 8 , 999.Xr diskinfo 8 , 1000.Xr disklabel64 8 , 1001.Xr fdisk 8 , 1002.Xr gpt 8 , 1003.Xr newfs 8 , 1004.Xr newfs_hammer 8 , 1005.Xr vinum 8 1006.Sh BUGS 1007For the i386 architecture, the primary bootstrap sector contains 1008an embedded 1009.Em fdisk 1010table. 1011The 1012.Nm 1013utility takes care to not clobber it when installing a bootstrap only 1014.Pq Fl B , 1015or when editing an existing label 1016.Pq Fl e , 1017but it unconditionally writes the primary bootstrap program onto 1018the disk for 1019.Fl w 1020or 1021.Fl R , 1022thus replacing the 1023.Em fdisk 1024table by the dummy one in the bootstrap program. 1025This is only of 1026concern if the disk is fully dedicated, so that the 1027.Bx 1028disklabel 1029starts at absolute block 0 on the disk. 1030.Pp 1031The 1032.Nm 1033utility 1034does not perform all possible error checking. 1035Warning 1036.Em is 1037given if partitions 1038overlap; if an absolute offset does not match the expected offset; if the 1039.Ql c 1040partition does not start at 0 or does not cover the entire slice; if a 1041partition runs past the end of the device; and a number of other errors; but 1042no warning is given if space remains unused. 1043