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. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94 32.\" $FreeBSD: src/sbin/disklabel/disklabel.8,v 1.15.2.22 2003/04/17 17:56:34 trhodes Exp $ 33.\" 34.Dd July 21, 2018 35.Dt DISKLABEL64 8 36.Os 37.Sh NAME 38.Nm disklabel64 39.Nd read and write 64 bit disk pack label 40.Sh SYNOPSIS 41.Nm 42.Op Fl r 43.Ar disk 44.Nm 45.Op Fl x 46.Ar disk 47.Nm 48.Fl w 49.Op Fl r 50.Op Fl n 51.Ar disk 52.Op Ar disktype Ns / Ns Cm auto Op Ar packid 53.Nm 54.Fl e 55.Op Fl r 56.Op Fl n 57.Ar disk 58.Nm 59.Fl R 60.Op Fl r 61.Op Fl n 62.Ar disk Ar protofile 63.Nm 64.Op Fl NW 65.Ar disk 66.Pp 67.Nm 68.Fl B 69.Oo 70.Fl b Ar boot1 71.Fl s Ar boot2 72.Oc 73.Ar disk 74.Oo Ar disktype Ns / Ns Cm auto Oc 75.Nm 76.Fl w 77.Fl B 78.Op Fl n 79.Oo 80.Fl b Ar boot1 81.Fl s Ar boot2 82.Oc 83.Ar disk 84.Op Ar disktype Ns / Ns Cm auto Op Ar packid 85.Nm 86.Fl R 87.Fl B 88.Op Fl n 89.Oo 90.Fl b Ar boot1 91.Fl s Ar boot2 92.Oc 93.Ar disk Ar protofile 94.Oo Ar disktype Ns / Ns Cm auto Oc 95.Sh DESCRIPTION 96The 97.Nm 98utility 99installs, examines or modifies a 64 bit label on a disk drive or pack. 100When writing 101the label, it can be used to change the drive identification, the disk 102partitions on the drive, or to replace a damaged label. 103There are several forms 104of the command that read (display), install or edit the label on a disk. 105In 106addition, 107.Nm 108can install bootstrap code. 109.Ss Raw or in-core label 110The disk label resides close to or at the beginning of each disk slice. 111For faster access, the kernel maintains a copy in core at all times. 112By 113default, most forms of the 114.Nm 115command access the in-core copy of the label. 116To access the raw (on-disk) 117copy, use the 118.Fl r 119option. 120This option allows a label to be installed on a disk without kernel 121support for a label, such as when labels are first installed on a system; it 122must be used when first installing a label on a disk. 123The specific effect of 124.Fl r 125is described under each command. 126.Ss Disk device name 127All 128.Nm 129forms require a disk device name, which should always be the raw 130device name representing the disk or slice. 131.Dx 132uses the following scheme for slice numbering: 133If the disk doesn't use GPT (typically laid out by 134.Xr gpt 8 ) , 135but e.g.\& MBR (typically laid out by 136.Xr fdisk 8 ) , 137then slice 0, e.g.\& 138.Pa da0s0 , 139represents the entire disk regardless of any DOS partitioning. 140Slice 0 is called the compatibility slice, 141and slice 1 and onward, e.g.\& 142.Pa da0s1 , 143represents a 144.Bx 145slice. 146If the disk does use GPT, then all slices are 147.Bx 148slices, slice 0 isn't special, it is just the first slice on the disk. 149You do not have to include the 150.Pa /dev/ 151path prefix when specifying the device. 152The 153.Nm 154utility will automatically prepend it. 155.Ss Reading the disk label 156To examine the label on a disk drive, use 157.Nm 158without options: 159.Pp 160.Nm 161.Op Fl r 162.Ar disk 163.Pp 164.Ar disk 165represents the raw disk in question, and may be in the form 166.Pa da0s1 167or 168.Pa /dev/da0s1 . 169It will display all of the parameters associated with the drive and its 170partition layout. 171Unless the 172.Fl r 173flag is given, 174the kernel's in-core copy of the label is displayed; 175if the disk has no label, or the partition types on the disk are incorrect, 176the kernel may have constructed or modified the label. 177If the 178.Fl r 179flag is given, 180.Nm 181reads the label from the raw disk and displays it. 182Both versions are usually 183identical except in the case where a label has not yet been initialized or 184is corrupt. 185.Ss Writing a standard label 186To write a standard label, use the form 187.Pp 188.Nm 189.Fl w 190.Op Fl r 191.Op Fl n 192.Ar disk 193.Op Ar disktype Ns / Ns Cm auto Op Ar packid 194.Pp 195The required argument to 196.Nm 197is the drive to be labeled. 198The first optional argument is the drive type as described in the 199.Xr disktab 5 200file, from which the drive parameters and partitions are taken. 201If not specified, then the 202.Cm auto 203type is assumed to make a virgin label for the disk as described below. 204If 205different disks of the same physical type are to have different partitions, it 206will be necessary to have separate disktab entries describing each, or to edit 207the label after installation as described below. 208The optional argument is a 209pack identification string, up to 63 characters long. 210The pack id must be 211quoted if it contains blanks. 212.Pp 213If the 214.Fl n 215flag is given, no data will be written to the device, and instead the 216disklabel that would have been written will be printed to stdout. 217.Pp 218If the 219.Fl r 220flag is given, the disk sectors containing the label and bootstrap 221will be written directly. 222A side-effect of this is that any existing bootstrap code will be overwritten 223and the disk rendered unbootable. 224See the boot options below for a method of 225writing the label and the bootstrap at the same time. 226If 227.Fl r 228is not specified, 229the existing label will be updated via the in-core copy and any bootstrap 230code will be unaffected. 231If the disk does not already have a label, the 232.Fl r 233flag must be used. 234In either case, the kernel's in-core label is replaced. 235.Pp 236For a virgin disk that is not known to 237.Xr disktab 5 , 238.Ar disktype 239can be specified as 240.Cm auto . 241In this case, the driver is requested to produce a virgin label for the 242disk. 243This might or might not be successful, depending on whether the 244driver for the disk is able to get the required data without reading 245anything from the disk at all. 246It will likely succeed for all SCSI 247disks, most IDE disks, and vnode devices. 248Writing a label to the 249disk is the only supported operation. 250.Pp 251For most harddisks, a label based on percentages for most partitions (and 252one partition with a size of 253.Ql * ) 254will produce a reasonable configuration. 255.Pp 256PC-based systems have special requirements in order for the BIOS to properly 257recognize a 258.Dx 259disklabel. 260Older systems may require what is known as a 261.Dq dangerously dedicated 262disklabel, which creates a fake DOS partition to work around problems older 263BIOSes have with modern disk geometries. 264On newer systems you generally want 265to create a normal DOS partition using 266.Ar fdisk 267and then create a 268.Dx 269disklabel within that slice. 270This is described 271later on in this page. 272.Pp 273Installing a new disklabel does not in of itself allow your system to boot 274a kernel using that label. 275You must also install boot blocks, which is 276described later on in this manual page. 277.Ss Editing an existing disk label 278To edit an existing disk label, use the form 279.Pp 280.Nm 281.Fl e 282.Op Fl r 283.Op Fl n 284.Ar disk 285.Pp 286This command reads the label from the in-core kernel copy, or directly from the 287disk if the 288.Fl r 289flag is also specified. 290The label is written to a file in ASCII and then 291supplied to an editor for changes. 292If no editor is specified in an 293.Ev EDITOR 294environment variable, 295.Xr vi 1 296is used. 297When the editor terminates, the label file is used to rewrite the disk label. 298Existing bootstrap code is unchanged regardless of whether 299.Fl r 300was specified. 301If 302.Fl n 303is specified, no data will be written to the device, and instead the 304disklabel that would have been written will be printed to stdout. 305This is 306useful to see how a partitioning scheme will work out for a specific disk. 307.Ss Restoring a disk label from a file 308To restore a disk label from a file, use the form 309.Pp 310.Nm 311.Fl R 312.Op Fl r 313.Op Fl n 314.Ar disk Ar protofile 315.Pp 316.Nm 317is capable of restoring a disk label that was previously saved in a file 318in ASCII format. 319The prototype file used to create the label should be in the same format 320as that produced when reading or editing a label. 321Comments are delimited by 322.Ql # 323and newline. 324As when writing a new label, any existing bootstrap code will be 325clobbered if 326.Fl r 327is specified and will be unaffected otherwise. 328See the boot options below for a 329method of restoring the label and writing the bootstrap at the same time. 330If 331.Fl n 332is used, no data will be written to the device, and instead the 333disklabel that would have been written will be printed to stdout. 334This is 335useful to see how a partitioning scheme will work out for a specific disk. 336.Ss Enabling and disabling writing to the disk label area 337By default, it is not possible to write to the disk label area at the beginning 338of a disk. 339The disk driver arranges for 340.Xr write 2 341and similar system calls 342to return 343.Er EROFS 344on any attempt to do so. 345If you need 346to write to this area (for example, to obliterate the label), use the form 347.Pp 348.Nm 349.Fl W 350.Ar disk 351.Pp 352To disallow writing to the label area after previously allowing it, 353use the command 354.Pp 355.Nm 356.Fl N 357.Ar disk 358.Ss Installing bootstraps 359The final three forms of 360.Nm 361are used to install bootstrap code, which allows boot from a 362.Xr HAMMER 5 , 363.Xr HAMMER2 5 , 364or 365.Xr UFS 5 366file system. 367If you are creating a 368.Dq dangerously-dedicated 369slice for compatibility with older PC systems, 370you generally want to specify the compatibility slice, such as 371.Pa da0s0 . 372If you are creating a label within an existing DOS slice, 373you should specify 374the slice name such as 375.Pa da0s1 . 376Making a slice bootable can be tricky. 377If you are using a normal DOS 378slice you typically install (or leave) a standard MBR on the base disk and 379then install the 380.Dx 381bootblocks in the slice. 382.Pp 383.Nm 384.Fl B 385.Oo 386.Fl b Ar boot1 387.Fl s Ar boot2 388.Oc 389.Ar disk 390.Oo Ar disktype Ns / Ns Cm auto Oc 391.Pp 392This form installs the bootstrap only. 393It does not change the disk label. 394You should never use this command on the compatibility slice unless you 395intend to create a 396.Dq dangerously-dedicated 397disk, such as 398.Ar da0s0 . 399This command is typically run on a 400.Bx 401slice such as 402.Ar da0s1 . 403.Pp 404.Nm 405.Fl w 406.Fl B 407.Op Fl n 408.Oo 409.Fl b Ar boot1 410.Fl s Ar boot2 411.Oc 412.Ar disk 413.Op Ar disktype Ns / Ns Cm auto Op Ar packid 414.Pp 415This form corresponds to the 416.Dq write label 417command described above. 418In addition to writing a new volume label, it also installs the bootstrap. 419If run on the compatibility slice this command will create a 420.Dq dangerously-dedicated 421label. 422This command is normally run on a 423.Bx 424slice rather than the compatibility slice. 425If 426.Fl n 427is used, no data will be written to the device, and instead the 428disklabel that would have been written will be printed to stdout. 429.Pp 430.Nm 431.Fl R 432.Fl B 433.Op Fl n 434.Oo 435.Fl b Ar boot1 436.Fl s Ar boot2 437.Oc 438.Ar disk Ar protofile 439.Oo Ar disktype Ns / Ns Cm auto Oc 440.Pp 441This form corresponds to the 442.Dq restore label 443command described above. 444In addition to restoring the volume label, it also installs the bootstrap. 445If run on the compatibility slice this command will create a 446.Dq dangerously-dedicated 447label. 448This command is normally run on a 449.Bx 450slice rather than the compatibility 451slice. 452.Pp 453The bootstrap commands always access the disk directly, 454so it is not necessary to specify the 455.Fl r 456flag. 457If 458.Fl n 459is used, no data will be written to the device, and instead the 460disklabel that would have been written will be printed to stdout. 461.Pp 462The bootstrap code is comprised of two boot programs. 463Specify the name of the 464boot programs to be installed in one of these ways: 465.Bl -enum 466.It 467Specify the names explicitly with the 468.Fl b 469and 470.Fl s 471flags. 472.Fl b 473indicates the primary boot program and 474.Fl s 475the secondary boot program. 476The boot programs are normally located in 477.Pa /boot . 478.It 479If the 480.Fl b 481and 482.Fl s 483flags are not specified, but 484.Ar disktype 485was specified, the names of the programs are taken from the 486.Dq b0 487and 488.Dq b1 489parameters of the 490.Xr disktab 5 491entry for the disk if the disktab entry exists and includes those parameters. 492.It 493Otherwise, the default boot image names are used: 494.Pa /boot/boot1_64 495and 496.Pa /boot/boot2_64 497for the standard stage1 and stage2 boot images. 498.El 499.Ss Initializing/Formatting a bootable disk from scratch 500To initialize a disk from scratch the following sequence is recommended. 501Please note that this will wipe everything that was previously on the disk, 502including any 503.No non- Ns Dx 504slices. 505.Bl -enum 506.It 507Use 508.Xr gpt 8 509or 510.Xr fdisk 8 511to initialize the hard disk, and create a GPT or MBR slice table, 512referred to as the 513.Dq "partition table" 514in 515.Tn DOS . 516.It 517Use 518.Nm 519or 520.Xr disklabel32 8 521to define partitions on 522.Dx 523slices created in the previous step. 524.It 525Finally use 526.Xr newfs_hammer 8 , 527.Xr newfs_hammer2 8 , 528or 529.Xr newfs 8 530to create file systems on new partitions. 531.El 532.Pp 533A typical partitioning scheme would be to have an 534.Ql a 535partition of approximately 1 GB for 536.Pa /boot 537to hold the current, old (and backup) kernels and modules, a 538.Ql b 539partition for swap (suggested to be at least the same size as the 540physical memory), 541and finally a 542.Ql d 543partition for the root file system (usually all remaining space). 544Your mileage may vary. 545.Pp 546.Dl "gpt init -f -B da0" 547.Dl "disklabel64 -B -r -w da0s1" 548.Dl "disklabel64 -e da0s1" 549.Ss Expanding the disklabel 550The 551.Fl x[x] 552option may be used to expand an existing disklabel to cover an expanded 553storage device. This is useful when an image is copied to larger underlying 554storage. If specified twice, the last partition will also be expanded to 555fill the area. Mounted HAMMER2 filesystems can also be expanded to cover 556the new space in the partition. 557.Pp 558.Dl "gpt expand da0" 559.Dl "disklabel64 -xx da0s1" 560.Dl "hammer2 growfs /blahblah" 561.Sh ALIGNMENT 562When a virgin disklabel64 is laid down a 563.Dx 2.5 564or later kernel will align the partition start offset relative to the 565physical drive instead of relative to the slice start. 566This overcomes the issue of fdisk creating a badly aligned slice by default. 567The kernel will use a 1MiB (1024 * 1024 byte) alignment. 568The purpose of this alignment is to match swap and cluster operations 569against the physical block size of the underlying device. 570.Pp 571Even though nearly all devices still report a logical sector size of 512, 572newer hard drives are starting to use larger physical sector sizes 573and, in particular, solid state drives (SSDs) use a physical block size 574of 64K (SLC) or 128K (MLC). We choose a 1 megabyte alignment to cover our 575bases down the road. 64-bit disklabels are not designed to be put on 576ultra-tiny storage devices. 577.Pp 578It is worth noting that aligning cluster operations is particularly 579important for SSDs and doubly so when 580.Xr swapcache 8 581is used with a SSD. 582Swapcache is able to use large bulk writes which greatly reduces the degree 583of write magnification on SSD media and it is possible to get upwards of 5845x more endurance out of the device than the vendor spec sheet indicates. 585.Sh FILES 586.Bl -tag -width ".Pa /boot/boot2_64" -compact 587.It Pa /boot/boot1_64 588Default stage1 boot image. 589.It Pa /boot/boot2_64 590Default stage2 boot image. 591.It Pa /etc/disktab 592Disk description file. 593.El 594.Sh SAVED FILE FORMAT 595The 596.Nm 597utility uses an 598.Tn ASCII 599version of the label when examining, editing, or restoring a disk label. 600An example shows as below: 601.Bd -literal -offset 4n 602# /dev/ad0s1: 603# 604# Calculated informational fields for the slice: 605# 606# boot space: 1012224 bytes 607# data space: 156286976 blocks # 152624.00 MB (160037863424 bytes) 608# 609# NOTE: The partition data base and stop are physically 610# aligned instead of slice-relative aligned. 611# 612# All byte equivalent offsets must be aligned. 613# 614diskid: 5dc53a64-c5e5-11e7-8aec-011d0988acd3 615label: 616boot2 data base: 0x000000001000 617partitions data base: 0x0000000f8200 618partitions data stop: 0x0025430f8200 619backup label: 0x002543157200 620total size: 0x002543158200 # 152625.34 MB 621alignment: 4096 622display block size: 1024 # for partition display and edit only 623 62416 partitions: 625# size offset fstype fsuuid 626 a: 1048576 0 4.2BSD # 1024.000MB 627 b: 16777216 1048576 swap # 16384.000MB 628 d: 138461184 17825792 HAMMER # 135216.000MB 629 a-stor_uuid: 7f1ff0ee-c5ec-11e7-8aec-011d0988acd3 630 b-stor_uuid: 7f1ff0fc-c5ec-11e7-8aec-011d0988acd3 631 d-stor_uuid: 7f1ff108-c5ec-11e7-8aec-011d0988acd3 632.Ed 633.Pp 634Lines starting with a 635.Ql # 636mark are comments. 637The specifications which can be changed are: 638.Bl -inset 639.It Ar label 640is an optional label, set by the 641.Ar packid 642option when writing a label. 643.It Ar "the partition table" 644is the 645.Ux 646partition table, not the 647.Tn DOS 648partition table described in 649.Xr fdisk 8 . 650.El 651.Pp 652The partition table can have up to 16 entries. 653It contains the following information: 654.Bl -tag -width indent 655.It Ar # 656The partition identifier is a single letter in the range 657.Ql a 658to 659.Ql p . 660.It Ar size 661The size of the partition in sectors, 662.Cm K 663(kilobytes - 1024), 664.Cm M 665(megabytes - 1024*1024), 666.Cm G 667(gigabytes - 1024*1024*1024), 668.Cm T 669(terabytes - 1024*1024*1024*1024), 670.Cm % 671(percentage of free space 672.Em after 673removing any fixed-size partitions), 674.Cm * 675(all remaining free space 676.Em after 677fixed-size and percentage partitions). 678Lowercase versions of 679.Cm K , M , G , 680and 681.Cm T 682are allowed. 683Size and type should be specified without any spaces between them. 684.Pp 685Example: 2097152, 1G, 1024M and 1048576K are all the same size 686(assuming 512-byte sectors). 687.It Ar offset 688The offset of the start of the partition from the beginning of the 689drive in sectors, or 690.Cm * 691to have 692.Nm 693calculate the correct offset to use (the end of the previous partition plus 694one. 695.It Ar fstype 696The name of the filesystem type for the partition (case insensitive). 697For 698.Xr UFS 5 699file systems, use type 700.Cm 4.2BSD . 701For 702.Xr HAMMER 5 703file systems, use type 704.Cm HAMMER . 705For 706.Xr hammer2 8 707file systems, use type 708.Cm HAMMER2 . 709For 710.Xr ccd 4 711partitions, use type 712.Cm ccd . 713For Vinum drives, use type 714.Cm vinum . 715Other common types are 716.Cm swap 717and 718.Cm unused . 719The 720.Nm 721utility 722also knows about a number of other partition types, 723none of which are in current use. 724(See 725.Dv fstypenames 726in 727.In sys/dtype.h 728for more details). 729.El 730.Pp 731The remainder of the line is a comment and shows the size of 732the partition in MB. 733.Sh EXAMPLES 734.Dl "disklabel64 da0s1" 735.Pp 736Display the in-core label for the first slice of the 737.Pa da0 738disk, as obtained via 739.Pa /dev/da0s1 . 740(If the disk is 741.Dq dangerously-dedicated , 742the compatibility slice name should be specified, such as 743.Pa da0s0 . ) 744.Pp 745.Dl "disklabel64 da0s1 > savedlabel" 746.Pp 747Save the in-core label for 748.Pa da0s1 749into the file 750.Pa savedlabel . 751This file can be used with the 752.Fl R 753option to restore the label at a later date. 754.Pp 755.Dl "disklabel64 -e -r da0s1" 756.Pp 757Read the on-disk label for 758.Pa da0s1 , 759edit it, and reinstall in-core as well as on-disk. 760Existing bootstrap code is unaffected. 761.Pp 762.Dl "disklabel64 -e -r -n da0s1" 763.Pp 764Read the on-disk label for 765.Pa da0s1 , 766edit it, and display what the new label would be. 767It does 768.Em not 769install the new label either in-core or on-disk. 770.Pp 771.Dl "disklabel64 -r -w da0s1" 772.Pp 773Try to auto-detect the required information from 774.Pa da0s1 , 775and write a new label to the disk. 776Use another 777.Nm Fl e 778command to edit the partitioning information. 779.Pp 780.Dl "disklabel64 -R da0s1 savedlabel" 781.Pp 782Restore the on-disk and in-core label for 783.Pa da0s1 784from information in 785.Pa savedlabel . 786Existing bootstrap code is unaffected. 787.Pp 788.Dl "disklabel64 -R -n da0s1 label_layout" 789.Pp 790Display what the label would be for 791.Pa da0s1 792using the partition layout in 793.Pa label_layout . 794This is useful for determining how much space would be allotted for various 795partitions with a labelling scheme using 796.Cm % Ns -based 797or 798.Cm * 799partition sizes. 800.Pp 801.Dl "disklabel64 -B da0s1" 802.Pp 803Install a new bootstrap on 804.Pa da0s1 . 805The boot code comes from 806.Pa /boot/boot1_64 807and possibly 808.Pa /boot/boot2_64 . 809On-disk and in-core labels are unchanged. 810.Pp 811.Dl "disklabel64 -w -B /dev/da0s1 -b newboot1 -s newboot2" 812.Pp 813Install a new label and bootstrap, with bootstrap code comes from the files 814.Pa newboot1 815and 816.Pa newboot2 . 817.Pp 818.Dl "dd if=/dev/zero of=/dev/da0 bs=512 count=32" 819.Dl "fdisk -BI da0" 820.Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32" 821.Dl "disklabel64 -w -B da0s1" 822.Dl "disklabel64 -e da0s1" 823.Pp 824Completely wipe any prior information on the disk, creating a new bootable 825disk with a DOS partition table containing one 826.Dq whole-disk 827slice. 828Then 829initialize the slice, then edit it to your needs. 830The 831.Pa dd 832commands are optional, but may be necessary for some BIOSes to properly 833recognize the disk. 834.Pp 835.Dl "disklabel64 -W da0s1" 836.Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32" 837.Dl "disklabel32 -r -w da0s1" 838.Dl "disklabel32 -N da0s1" 839.Pp 840Completely wipe any prior information on the slice, 841and install the old 32-bit label. 842The wiping is needed because both 843.Nm disklabel32 844and 845.Nm , 846as a safety measure, 847won't do any operations if label with other format is already installed. 848.Pp 849This is an example disklabel that uses some of the new partition size types 850such as 851.Cm % , M , G , T , 852and 853.Cm * , 854which could be used as a source file for: 855.Pp 856.Dl "disklabel64 -R ad0s1 new_label_file" 857.Bd -literal -offset 4n 858# /dev/ad0s1: 859# 860# Calculated informational fields for the slice: 861# 862# boot space: 1012224 bytes 863# data space: 156286976 blocks # 152624.00 MB (160037863424 bytes) 864# 865# NOTE: The partition data base and stop are physically 866# aligned instead of slice-relative aligned. 867# 868# All byte equivalent offsets must be aligned. 869# 870diskid: 5dc53a64-c5e5-11e7-8aec-011d0988acd3 871label: 872boot2 data base: 0x000000001000 873partitions data base: 0x0000000f8200 874partitions data stop: 0x0025430f8200 875backup label: 0x002543157200 876total size: 0x002543158200 # 152625.34 MB 877alignment: 4096 878display block size: 1024 # for partition display and edit only 879 88016 partitions: 881# size offset fstype fsuuid 882 a: 1024M 0 4.2BSD 883 b: 4G * swap 884 d: 2G * 4.2BSD 885 e: 2048M * 4.2BSD 886 f: 4G * 4.2BSD 887 g: 4G * 4.2BSD 888 h: 50G * HAMMER 889 i: * * HAMMER2 890 j: 5g * ccd 891 k: 5120m * vinum 892.Ed 893.Sh DIAGNOSTICS 894The kernel device drivers will not allow the size of a disk partition 895to be decreased or the offset of a partition to be changed while it is open. 896Some device drivers create a label containing only a single large partition 897if a disk is unlabeled; thus, the label must be written to the 898.Ql a 899partition of the disk while it is open. 900This sometimes requires the desired 901label to be set in two steps, the first one creating at least one other 902partition, and the second setting the label on the new partition while 903shrinking the 904.Ql a 905partition. 906.Sh SEE ALSO 907.Xr dd 1 , 908.Xr uuid 3 , 909.Xr ccd 4 , 910.Xr disklabel64 5 , 911.Xr disktab 5 , 912.Xr boot0cfg 8 , 913.Xr diskinfo 8 , 914.Xr disklabel32 8 , 915.Xr fdisk 8 , 916.Xr gpt 8 , 917.Xr hammer2 8 , 918.Xr newfs 8 , 919.Xr newfs_hammer 8 , 920.Xr newfs_hammer2 8 , 921.Xr vinum 8 922.Sh BUGS 923The 924.Nm 925utility 926does not perform all possible error checking. 927Warning 928.Em is 929given if partitions 930overlap; if an absolute offset does not match the expected offset; if a 931partition runs past the end of the device; and a number of other errors; but 932no warning is given if space remains unused. 933.Pp 934The 935.Xr disktab 5 936support is not implemented. 937