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.\" $FreeBSD$ 37.\" 38.Dd July 30, 1999 39.Dt DISKLABEL 8 40.Os 41.Sh NAME 42.Nm disklabel 43.Nd read and write disk pack label 44.Sh SYNOPSIS 45.Nm 46.Op Fl r 47.Ar disk 48.Nm 49.Fl w 50.Op Fl r 51.Op Fl n 52.Ar disk Ar disktype/auto 53.Oo Ar packid Oc 54.Nm 55.Fl e 56.Op Fl r 57.Op Fl n 58.Ar disk 59.Nm 60.Fl R 61.Op Fl r 62.Op Fl n 63.Ar disk Ar protofile 64.Nm 65.Op Fl NW 66.Ar disk 67.Pp 68.Nm 69.Fl B 70.Oo 71.Fl b Ar boot1 72.Fl s Ar boot2 73.Oc 74.Ar disk 75.Oo Ar disktype/auto Oc 76.Nm 77.Fl w 78.Fl B 79.Op Fl n 80.Oo 81.Fl b Ar boot1 82.Fl s Ar boot2 83.Oc 84.Ar disk Ar disktype/auto 85.Oo Ar packid Oc 86.Nm 87.Fl R 88.Fl B 89.Op Fl n 90.Oo 91.Fl b Ar boot1 92.Fl s Ar boot2 93.Oc 94.Ar disk Ar protofile 95.Oo Ar disktype/auto Oc 96.Sh DESCRIPTION 97The 98.Nm 99utility 100installs, examines or modifies the label on a disk drive or pack. When writing 101the label, it can be used to change the drive identification, the disk 102partitions on the drive, or to replace a damaged label. There are several forms 103of the command that read (display), install or edit the label on a disk. In 104addition, 105.Nm 106can install bootstrap code. 107.Ss Raw or in-core label 108.Pp 109The disk label resides close to or at the beginning of each disk slice. 110For faster access, the kernel maintains a copy in core at all times. By 111default, most 112.Nm 113access the in-core copy of the label. To access the raw (on-disk) copy, use the 114.Fl r 115option. This option allows a label to be installed on a disk without kernel 116support for a label, such as when labels are first installed on a system; it 117must be used when first installing a label on a disk. The specific effect of 118.Fl r 119is described under each command. 120.Pp 121.Ss Disk device name 122.Pp 123All 124.Nm 125forms require a disk device name, which should always be the raw 126device name representing the disk or slice. For example 127.Pa da0 128represents the entire disk regardless of any DOS partitioning, 129and 130.Pa da0s1 131represents a slice. Some devices, most notably 132.Ar ccd , 133require that the 134.Dq whole-disk 135(or 136.Dq c ) 137partition be specified. For example 138.Pa ccd0c . 139You do not have to include the 140.Pa /dev/ 141path prefix when specifying the device. 142The 143.Nm 144utility will automatically prepend it. 145.Ss Reading the disk label 146.Pp 147To examine the label on a disk drive, use 148.Nm 149without options: 150.Pp 151.Nm 152.Op Fl r 153.Ar disk 154.Pp 155.Ar disk 156represents the raw disk in question, and may be in the form 157.Pa da0 158or 159.Pa /dev/da0c . 160It will display all of the parameters associated with the drive and its 161partition layout. Unless the 162.Fl r 163flag is given, 164the kernel's in-core copy of the label is displayed; 165if the disk has no label, or the partition types on the disk are incorrect, 166the kernel may have constructed or modified the label. 167If the 168.Fl r 169flag is given, 170.Nm 171reads the label from the raw disk and displays it. Both versions are usually 172identical except in the case where a label has not yet been initialized or 173is corrupt. 174.Ss Writing a standard label 175.Pp 176To write a standard label, use the form 177.Pp 178.Nm 179.Fl w 180.Op Fl r 181.Op Fl n 182.Ar disk Ar disktype/auto 183.Oo Ar packid Oc 184.Pp 185.Nm 186.Fl w 187.Op Fl r 188.Op Fl n 189.Ar disk 190auto 191.Pp 192The required arguments to 193.Nm 194are the drive to be labeled and the drive type as described in the 195.Xr disktab 5 196file. The drive parameters and partitions are taken from that file. If 197different disks of the same physical type are to have different partitions, it 198will be necessary to have separate disktab entries describing each, or to edit 199the label after installation as described below. The optional argument is a 200pack identification string, up to 16 characters long. The pack id must be 201quoted if it contains blanks. 202.Pp 203If the 204.Fl n 205flag is given, no data will be written to the device, and instead the 206disklabel that would have been written will be printed to stdout. 207.Pp 208If the 209.Fl r 210flag is given, the disk sectors containing the label and bootstrap 211will be written directly. 212A side-effect of this is that any existing bootstrap code will be overwritten 213and the disk rendered unbootable. See the boot options below for a method of 214writing the label and the bootstrap at the same time. 215If 216.Fl r 217is not specified, 218the existing label will be updated via the in-core copy and any bootstrap 219code will be unaffected. 220If the disk does not already have a label, the 221.Fl r 222flag must be used. 223In either case, the kernel's in-core label is replaced. 224.Pp 225For a virgin disk that is not known to 226.Xr disktab 5 , 227.Ar disktype 228can be specified as 229.Dq auto . 230In this case, the driver is requested to produce a virgin label for the 231disk. This might or might not be successful, depending on whether the 232driver for the disk is able to get the required data without reading 233anything from the disk at all. It will likely succeed for all SCSI 234disks, most IDE disks, and vnode devices. Writing a label to the 235disk is the only supported operation, and the 236.Ar disk 237itself must be provided as the canonical name, i.e. not as a full 238path name. 239.Pp 240For most harddisks, a label based on percentages for most partitions (and 241one partition with a size of 242.Ql * ) 243will produce a reasonable configuration. 244.Pp 245PC-based systems have special requirements in order for the BIOS to properly 246recognize a 247.Fx 248disklabel. Older systems may require what is known as a 249.Dq dangerously dedicated 250disklabel, which creates a fake DOS partition to work around problems older 251BIOSes have with modern disk geometries. 252On newer systems you generally want 253to create a normal DOS partition using 254.Ar fdisk 255and then create a 256.Fx 257disklabel within that slice. This is described 258later on in this page. 259.Pp 260Installing a new disklabel does not in of itself allow your system to boot 261a kernel using that label. You must also install boot blocks, which is 262described later on in this manual page. 263.Ss Editing an existing disk label 264.Pp 265To edit an existing disk label, use the form 266.Pp 267.Nm 268.Fl e 269.Op Fl r 270.Op Fl n 271.Ar disk 272.Pp 273This command reads the label from the in-core kernel copy, or directly from the 274disk if the 275.Fl r 276flag is also specified. The label is written to a file in ASCII and then 277supplied to an editor for changes. If no editor is specified in an 278.Ev EDITOR 279environment variable, 280.Xr vi 1 281is used. When the editor terminates, the label file is used to rewrite the disk 282label. Existing bootstrap code is unchanged regardless of whether 283.Fl r 284was specified. If 285.Fl n 286is specified, no data will be written to the device, and instead the 287disklabel that would have been written will be printed to stdout. This is 288useful to see how a partitioning scheme will work out for a specific disk. 289.Ss Restoring a disk label from a file 290.Pp 291To restore a disk label from a file, use the form 292.Pp 293.Nm 294.Fl R 295.Op Fl r 296.Op Fl n 297.Ar disk Ar protofile 298.Pp 299.Nm 300is capable of restoring a disk label that was previously saved in a file in ASCII format. 301The prototype file used to create the label should be in the same format as that 302produced when reading or editing a label. Comments are delimited by 303.Ar \&# 304and newline. As when writing a new label, any existing bootstrap code will be 305clobbered if 306.Fl r 307is specified and will be unaffected otherwise. See the boot options below for a 308method of restoring the label and writing the bootstrap at the same time. 309If 310.Fl n 311is used, no data will be written to the device, and instead the 312disklabel that would have been written will be printed to stdout. This is 313useful to see how a partitioning scheme will work out for a specific disk. 314.Ss Enabling and disabling writing to the disk label area 315.Pp 316By default, it is not possible to write to the disk label area at the beginning 317of a disk. The disk driver silently ignores any attempt to do so. If you need 318to write to this area (for example, to obliterate the label), use the form 319.Pp 320.Nm 321.Fl W 322.Ar disk 323.Pp 324To disallow writing to the label area after previously allowing it, use the 325command 326.Pp 327.Nm 328.Fl N 329.Ar disk 330.Ss Installing bootstraps 331.Pp 332The final three forms of 333.Nm 334are used to install bootstrap code. If you are creating a 335.Dq dangerously-dedicated 336slice for compatibility with older PC systems, 337you generally want to specify the raw disk name such as 338.Pa da0 . 339If you are creating a label within an existing DOS slice, 340you should specify 341the partition name such as 342.Pa da0s1a . 343Making a slice bootable can be tricky. If you are using a normal DOS 344slice you typically install (or leave) a standard MBR on the base disk and 345then install the 346.Fx 347bootblocks in the slice. 348.Pp 349.Nm 350.Fl B 351.Oo 352.Fl b Ar boot1 353.Fl s Ar boot2 354.Oc 355.Ar disk 356.Oo Ar disktype Oc 357.Pp 358This form installs the bootstrap only. It does not change the disk label. 359You should never use this command on a base disk unless you intend to create a 360.Dq dangerously-dedicated 361disk, such as 362.Ar da0 . 363This command is typically run on a slice such as 364.Ar da0s1 . 365.Pp 366.Nm 367.Fl w 368.Fl B 369.Op Fl n 370.Oo 371.Fl b Ar boot1 372.Fl s Ar boot2 373.Oc 374.Ar disk Ar disktype 375.Oo Ar packid Oc 376.Pp 377This form corresponds to the 378.Dq write label 379command described above. 380In addition to writing a new volume label, it also installs the bootstrap. 381If run on a base disk this command will create a 382.Dq dangerously-dedicated 383label. This command is normally run on a slice rather than a base disk. 384If 385.Fl n 386is used, no data will be written to the device, and instead the 387disklabel that would have been written will be printed to stdout. 388.Pp 389.Nm 390.Fl R 391.Fl B 392.Op Fl n 393.Oo 394.Fl b Ar boot1 395.Fl s Ar boot2 396.Oc 397.Ar disk Ar protofile 398.Oo Ar disktype Oc 399.Pp 400This form corresponds to the 401.Dq restore label 402command described above. 403In addition to restoring the volume label, it also installs the bootstrap. 404If run on a base disk this command will create a 405.Dq dangerously-dedicated 406label. This command is normally run on a slice rather than a base disk. 407.Pp 408The bootstrap commands always access the disk directly, so it is not necessary 409to specify the 410.Fl r 411flag. If 412.Fl n 413is used, no data will be written to the device, and instead the 414disklabel that would have been written will be printed to stdout. 415.Pp 416The bootstrap code is comprised of two boot programs. Specify the name of the 417boot programs to be installed in one of these ways: 418.Bl -enum 419.It 420Specify the names explicitly with the 421.Fl b 422and 423.Fl s 424flags. 425.Fl b 426indicates the primary boot program and 427.Fl s 428the secondary boot program. The boot programs are located in 429.Pa /boot . 430.It 431If the 432.Fl b 433and 434.Fl s 435flags are not specified, but 436.Ar disktype 437was specified, the names of the programs are taken from the 438.Dq b0 439and 440.Dq b1 441parameters of the 442.Xr disktab 5 443entry for the disk if the disktab entry exists and includes those parameters. 444.It 445Otherwise, the default boot image names are used: 446.Pa /boot/boot1 447and 448.Pa /boot/boot2 449for the standard stage1 and stage2 boot images (details may vary 450on architectures like the Alpha, where only a single-stage boot is used). 451.El 452.Ss Initializing/Formatting a bootable disk from scratch 453.Pp 454To initialize a disk from scratch the following sequence is recommended. 455Please note that this will wipe everything that was previously on the disk, 456including any 457.No non- Ns Fx 458slices. 459.Bl -enum 460.It 461Use 462.Xr fdisk 8 463to initialize the hard disk, and create a slice table, referred to 464as the partition table in DOS. 465Here you will define disk slices for your system. 466.It 467Use 468.Xr disklabel 8 469to define and write partitions and mount points. 470You are not required to define the mount points here though, 471they can be defined later using 472.Xr mount 8 . 473.It 474Finally use 475.Xr newfs 8 476to create a filesystem on the new partition. 477A typical partitioning scheme would be to have an 478.Dq a 479partition 480of approximately 128MB to hold the root filesystem, a 481.Dq b 482partition for 483swap, a 484.Dq d 485partition for /var (usually 128MB), an 486.Dq e 487partition 488for /var/tmp (usually 128MB), an 489.Dq f 490partition for /usr (usually around 2G), 491and finally a 492.Dq g 493partition for /home (usually all remaining space). 494Your mileage may vary. 495.El 496.Pp 497.Nm fdisk Fl BI Ar da0 498.Pp 499.Nm 500.Fl w 501.Fl B 502.Ar da0s1 503auto 504.Pp 505.Pp 506.Nm 507.Fl e 508.Ar da0s1 509.Sh FILES 510.Bl -tag -width Pa -compact 511.It Pa /etc/disktab 512.It Pa /boot/ 513.It Pa /boot/boot<n> 514.El 515.Sh SAVED FILE FORMAT 516The 517.Nm 518utility 519uses an ASCII version of the label when examining, editing or restoring a disk 520label. The format is: 521.Bd -literal -offset 4n 522# /dev/da1c: 523type: SCSI 524disk: da0s1 525label: 526flags: 527bytes/sector: 512 528sectors/track: 51 529tracks/cylinder: 19 530sectors/cylinder: 969 531cylinders: 1211 532sectors/unit: 1173930 533rpm: 3600 534interleave: 1 535trackskew: 0 536cylinderskew: 0 537headswitch: 0 # milliseconds 538track-to-track seek: 0 # milliseconds 539drivedata: 0 540 5418 partitions: 542# size offset fstype [fsize bsize bps/cpg] 543 a: 81920 0 4.2BSD 1024 8192 16 # (Cyl. 0 - 84*) 544 b: 160000 81920 swap # (Cyl. 84* - 218*) 545 c: 1173930 0 unused 0 0 # (Cyl. 0 - 1211*) 546 h: 962010 211920 vinum # (Cyl. 218*- 1211*) 547.Ed 548.Pp 549Lines starting with a # mark are comments. Most of the other specifications are 550no longer used. The ones which must still be set correctly are: 551.Pp 552.Bl -hang -width 20n 553.It Nm label 554is an optional label, set by the 555.Ar packid 556option when writing a label. 557.It Nm flags 558Flags may be 559.Ar removable , 560.Ar ecc 561or 562.Ar badsect . 563.Ar removable 564is set for removable media drives, but no current 565.Fx 566driver evaluates this 567flag. 568.Ar ecc 569is no longer supported; 570.Ar badsect 571specifies that the drive can perform bad sector remapping. 572.It Nm sectors/unit 573describes the total size of the disk. This value must be correct. 574.It Nm the partition table 575This is the 576.Ux 577partition table, not the Microsoft partition table described in 578.Xr fdisk 8 . 579.El 580.Pp 581The partition table can have up to 8 entries. It contains the following 582information: 583.Bl -hang -width 10n 584.It identifier 585The partition identifier is a single letter in the range 586.Dq a 587to 588.Dq h . 589By convention, partition 590.Dq c 591is reserved to describe the entire disk. 592.It size 593is the size of the partition in sectors, 594.Cm K 595(kilobytes - 1024), 596.Cm M 597(megabytes - 1024*1024), 598.Cm G 599(gigabytes - 1024*1024*1024), 600.Cm % 601(percentage of free space AFTER removing any fixed-size partitions other 602than partition 603.Dq c) , 604or 605.Cm * 606(all remaining free space AFTER fixed-size and percentage 607partitions). For partition 608.Dq c , 609a size of 610.Cm * 611indicates the entire disk. Lowercase versions of 612.Cm K , M , 613and 614.Cm G 615are allowed. 616Size and type should be specifed without any spaces between them. 617.Pp 618Example: 2097152, 1g, 1024m and 1048576k are all the same size 619(assuming 512-byte sectors). 620.It offset 621is the offset of the start of the partition from the beginning of the 622drive in sectors, or 623.Cm * 624to have 625.Nm 626calculate the correct offset to use (the end of the previous partition plus 627one, ignoring partition 628.Dq c . 629For partition 630.Dq c , 631.Cm * 632will be interpreted as an offset of 0. 633.It fstype 634describes the purpose of the partition. The example shows all currently used 635partition types. 636For UFS filesystems and ccd partitions, use type 637.Cm 4.2BSD . 638For Vinum drives, use type 639.Cm vinum . 640Other common types are 641.Cm unused 642and 643.Cm swap . 644By convention, partition 645.Dq c 646represents the entire slice and should be of type 647.Cm unused , 648though 649.Nm 650does not enforce this convention. 651The 652.Nm 653utility 654also knows about a number of other partition types, none of which are in current 655use. 656See the definitions starting with 657.Dv FS_UNUSED 658in 659.Pa /usr/include/sys/disklabel.h 660for more details. 661.It fsize 662For 663.Cm 4.2BSD 664and LFS filesystems only, the fragment size. Defaults to 1024 for 665partitions smaller than 1 GB, 4096 for partitions 1GB or larger. 666.It bsize 667For 668.Cm 4.2BSD 669and LFS filesystems only, the block size. Defaults to 8192 for 670partitions smaller than 1 GB, 16384 for partitions 1GB or larger. 671.It bps/cpg 672For 673.Cm 4.2BSD 674filesystems, the number of cylinders in a cylinder group. For LFS file 675systems, the segment shift value. Defaults to 16 for 676partitions smaller than 1 GB, 64 for partitions 1GB or larger. 677.El 678.Pp 679The remainder of the line is a comment and shows the cylinder allocations based 680on the obsolete (but possibly correct) geometry information about the drive. 681The asterisk (*) indicates that the partition does not begin or end exactly on a 682cylinder boundary. 683.Sh EXAMPLES 684.Dl disklabel da0 685.Pp 686Display the in-core label for 687.Pa da0s1 688as obtained via 689.Pa /dev/da0s1 . 690When reading a label, 691.Fx 692will allow you to specify the base disk name 693even if the label resides on a slice. However, to be proper you should 694specify the base disk name only if you are using a 695.Dq dangerously-dedicated 696label. Normally you specify the slice. 697.Pp 698.Dl disklabel da0s1 > savedlabel 699.Pp 700Save the in-core label for 701.Pa da0s1 702into the file 703.Pa savedlabel . 704This file can be used with the 705.Fl R 706flag to restore the label at a later date. 707.Pp 708.Dl disklabel -w -r /dev/da0s1 da2212 foo 709.Pp 710Create a label for 711.Pa da0s1 712based on information for 713.Dq da2212 714found in 715.Pa /etc/disktab . 716Any existing bootstrap code will be clobbered. 717.Pp 718.Dl disklabel -e -r da0s1 719.Pp 720Read the on-disk label for 721.Pa da0s1 , 722edit it and reinstall in-core as well as on-disk. Existing bootstrap code is 723unaffected. 724.Pp 725.Dl disklabel -e -r -n da0s1 726.Pp 727Read the on-disk label for 728.Pa da0s1 , 729edit it, and display what the new label would be (in sectors). It does 730NOT install the new label either in-core or on-disk. 731.Pp 732.Dl disklabel -r -w da0s1 auto 733.Pp 734Try to auto-detect the required information from 735.Pa da0s1 , 736and write a new label to the disk. Use another disklabel -e command to edit the 737partitioning and filesystem information. 738.Pp 739.Dl disklabel -R da0s1 savedlabel 740.Pp 741Restore the on-disk and in-core label for 742.Pa da0s1 743from information in 744.Pa savedlabel . 745Existing bootstrap code is unaffected. 746.Pp 747.Dl disklabel -R -n da0s1 label_layout 748.Pp 749Display what the label would be for 750.Pa da0s1 751using the partition layout in 752.Pa label_layout . 753This is useful for determining how much space would be alloted for various 754partitions with a labelling scheme using 755.Cm % Ns -based 756or 757.Cm * 758partition sizes. 759.Pp 760.Dl disklabel -B da0s1 761.Pp 762Install a new bootstrap on 763.Pa da0s1 . 764The boot code comes from 765.Pa /boot/boot1 766and possibly 767.Pa /boot/boot2 . 768On-disk and in-core labels are unchanged. 769.Pp 770.Dl disklabel -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212 771.Pp 772Install a new label and bootstrap. 773The label is derived from disktab information for 774.Dq da2212 775and installed both in-core and on-disk. 776The bootstrap code comes from the files 777.Pa /boot/newboot1 778and 779.Pa /boot/newboot2 . 780.Pp 781.Dl dd if=/dev/zero of=/dev/da0 bs=512 count=32 782.Dl fdisk -BI da0 783.Dl dd if=/dev/zero of=/dev/da0s1 bs=512 count=32 784.Dl disklabel -w -B da0s1 auto 785.Dl disklabel -e da0s1 786.Pp 787Completely wipe any prior information on the disk, creating a new bootable 788disk with a DOS partition table containing one 789.Dq whole-disk 790slice. Then 791initialize the slice, then edit it to your needs. The 792.Pa dd 793commands are optional, but may be necessary for some BIOSes to properly 794recognize the disk. 795.Pp 796This is an example disklabel that uses some of the new partition size types 797such as 798.Cm % , M , G , 799and 800.Cm * , 801which could be used as a source file for 802.Pp 803.Dl disklabel -R ad0s1c new_label_file 804.Bd -literal -offset 4n 805# /dev/ad0s1c: 806type: ESDI 807disk: ad0s1 808label: 809flags: 810bytes/sector: 512 811sectors/track: 63 812tracks/cylinder: 16 813sectors/cylinder: 1008 814cylinders: 40633 815sectors/unit: 40959009 816rpm: 3600 817interleave: 1 818trackskew: 0 819cylinderskew: 0 820headswitch: 0 # milliseconds 821track-to-track seek: 0 # milliseconds 822drivedata: 0 823 8248 partitions: 825# size offset fstype [fsize bsize bps/cpg] 826 a: 400M 0 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*) 827 b: 1G * swap 828 c: * * unused 829 e: 204800 * 4.2BSD 830 f: 5g * 4.2BSD 831 g: * * 4.2BSD 832.Ed 833.Sh SEE ALSO 834.Xr ccd 4 , 835.Xr disklabel 5 , 836.Xr disktab 5 , 837.Xr boot0cfg 8 , 838.Xr fdisk 8 , 839.Xr vinum 8 840.Sh DIAGNOSTICS 841The kernel device drivers will not allow the size of a disk partition 842to be decreased or the offset of a partition to be changed while it is open. 843Some device drivers create a label containing only a single large partition 844if a disk is unlabeled; thus, the label must be written to the 845.Dq a 846partition of the disk while it is open. This sometimes requires the desired 847label to be set in two steps, the first one creating at least one other 848partition, and the second setting the label on the new partition while shrinking 849the 850.Dq a 851partition. 852.Pp 853On some machines the bootstrap code may not fit entirely in the area 854allocated for it by some filesystems. 855As a result, it may not be possible to have filesystems on some partitions 856of a 857.Dq bootable 858disk. 859When installing bootstrap code, 860.Nm 861checks for these cases. 862If the installed boot code would overlap a partition of type FS_UNUSED 863it is marked as type FS_BOOT. 864The 865.Xr newfs 8 866utility will disallow creation of filesystems on FS_BOOT partitions. 867Conversely, if a partition has a type other than FS_UNUSED or FS_BOOT, 868.Nm 869will not install bootstrap code that overlaps it. 870.Sh BUGS 871When a disk name is given without a full pathname, 872the constructed device name uses the 873.Dq c 874partition. 875.Pp 876For the i386 architecture, the primary bootstrap sector contains 877an embedded 878.Em fdisk 879table. 880The 881.Nm 882utility takes care to not clobber it when installing a bootstrap only 883.Pq Fl B , 884or when editing an existing label 885.Pq Fl e , 886but it unconditionally writes the primary bootstrap program onto 887the disk for 888.Fl w 889or 890.Fl R , 891thus replacing the 892.Em fdisk 893table by the dummy one in the bootstrap program. This is only of 894concern if the disk is fully dedicated, so that the 895.Bx 896disklabel 897starts at absolute block 0 on the disk. 898.Pp 899The 900.Nm 901utility 902does not perform all possible error checking. Warning *is* given if partitions 903overlap; if an absolute offset does not match the expected offset; if the 904.Dq c 905partition does not start at 0 or does not cover the entire slice; if a 906partition runs past the end of the device; and a number of other errors; but 907no warning is given if space remains unused. 908