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 arranges for 318.Xr write 2 319and similar system calls 320to return EROFS on any attempt to do so. If you need 321to write to this area (for example, to obliterate the label), use the form 322.Pp 323.Nm 324.Fl W 325.Ar disk 326.Pp 327To disallow writing to the label area after previously allowing it, use the 328command 329.Pp 330.Nm 331.Fl N 332.Ar disk 333.Ss Installing bootstraps 334.Pp 335The final three forms of 336.Nm 337are used to install bootstrap code. If you are creating a 338.Dq dangerously-dedicated 339slice for compatibility with older PC systems, 340you generally want to specify the raw disk name such as 341.Pa da0 . 342If you are creating a label within an existing DOS slice, 343you should specify 344the partition name such as 345.Pa da0s1a . 346Making a slice bootable can be tricky. If you are using a normal DOS 347slice you typically install (or leave) a standard MBR on the base disk and 348then install the 349.Fx 350bootblocks in the slice. 351.Pp 352.Nm 353.Fl B 354.Oo 355.Fl b Ar boot1 356.Fl s Ar boot2 357.Oc 358.Ar disk 359.Oo Ar disktype Oc 360.Pp 361This form installs the bootstrap only. It does not change the disk label. 362You should never use this command on a base disk unless you intend to create a 363.Dq dangerously-dedicated 364disk, such as 365.Ar da0 . 366This command is typically run on a slice such as 367.Ar da0s1 . 368.Pp 369.Nm 370.Fl w 371.Fl B 372.Op Fl n 373.Oo 374.Fl b Ar boot1 375.Fl s Ar boot2 376.Oc 377.Ar disk Ar disktype 378.Oo Ar packid Oc 379.Pp 380This form corresponds to the 381.Dq write label 382command described above. 383In addition to writing a new volume label, it also installs the bootstrap. 384If run on a base disk this command will create a 385.Dq dangerously-dedicated 386label. This command is normally run on a slice rather than a base disk. 387If 388.Fl n 389is used, no data will be written to the device, and instead the 390disklabel that would have been written will be printed to stdout. 391.Pp 392.Nm 393.Fl R 394.Fl B 395.Op Fl n 396.Oo 397.Fl b Ar boot1 398.Fl s Ar boot2 399.Oc 400.Ar disk Ar protofile 401.Oo Ar disktype Oc 402.Pp 403This form corresponds to the 404.Dq restore label 405command described above. 406In addition to restoring the volume label, it also installs the bootstrap. 407If run on a base disk this command will create a 408.Dq dangerously-dedicated 409label. This command is normally run on a slice rather than a base disk. 410.Pp 411The bootstrap commands always access the disk directly, so it is not necessary 412to specify the 413.Fl r 414flag. If 415.Fl n 416is used, no data will be written to the device, and instead the 417disklabel that would have been written will be printed to stdout. 418.Pp 419The bootstrap code is comprised of two boot programs. Specify the name of the 420boot programs to be installed in one of these ways: 421.Bl -enum 422.It 423Specify the names explicitly with the 424.Fl b 425and 426.Fl s 427flags. 428.Fl b 429indicates the primary boot program and 430.Fl s 431the secondary boot program. The boot programs are located in 432.Pa /boot . 433.It 434If the 435.Fl b 436and 437.Fl s 438flags are not specified, but 439.Ar disktype 440was specified, the names of the programs are taken from the 441.Dq b0 442and 443.Dq b1 444parameters of the 445.Xr disktab 5 446entry for the disk if the disktab entry exists and includes those parameters. 447.It 448Otherwise, the default boot image names are used: 449.Pa /boot/boot1 450and 451.Pa /boot/boot2 452for the standard stage1 and stage2 boot images (details may vary 453on architectures like the Alpha, where only a single-stage boot is used). 454.El 455.Ss Initializing/Formatting a bootable disk from scratch 456.Pp 457To initialize a disk from scratch the following sequence is recommended. 458Please note that this will wipe everything that was previously on the disk, 459including any 460.No non- Ns Fx 461slices. 462.Bl -enum 463.It 464Use 465.Xr fdisk 8 466to initialize the hard disk, and create a slice table, referred to 467as the partition table in DOS. 468Here you will define disk slices for your system. 469.It 470Use 471.Xr disklabel 8 472to define and write partitions and mount points. 473You are not required to define the mount points here though, 474they can be defined later using 475.Xr mount 8 . 476.It 477Finally use 478.Xr newfs 8 479to create a file system on the new partition. 480A typical partitioning scheme would be to have an 481.Dq a 482partition 483of approximately 128MB to hold the root file system, a 484.Dq b 485partition for 486swap, a 487.Dq d 488partition for /var (usually 128MB), an 489.Dq e 490partition 491for /var/tmp (usually 128MB), an 492.Dq f 493partition for /usr (usually around 2G), 494and finally a 495.Dq g 496partition for /home (usually all remaining space). 497Your mileage may vary. 498.El 499.Pp 500.Nm fdisk Fl BI Ar da0 501.Pp 502.Nm 503.Fl w 504.Fl B 505.Ar da0s1 506auto 507.Pp 508.Pp 509.Nm 510.Fl e 511.Ar da0s1 512.Sh FILES 513.Bl -tag -width Pa -compact 514.It Pa /etc/disktab 515.It Pa /boot/ 516.It Pa /boot/boot<n> 517.El 518.Sh SAVED FILE FORMAT 519The 520.Nm 521utility 522uses an ASCII version of the label when examining, editing or restoring a disk 523label. The format is: 524.Bd -literal -offset 4n 525# /dev/da1c: 526type: SCSI 527disk: da0s1 528label: 529flags: 530bytes/sector: 512 531sectors/track: 51 532tracks/cylinder: 19 533sectors/cylinder: 969 534cylinders: 1211 535sectors/unit: 1173930 536rpm: 3600 537interleave: 1 538trackskew: 0 539cylinderskew: 0 540headswitch: 0 # milliseconds 541track-to-track seek: 0 # milliseconds 542drivedata: 0 543 5448 partitions: 545# size offset fstype [fsize bsize bps/cpg] 546 a: 81920 0 4.2BSD 1024 8192 16 # (Cyl. 0 - 84*) 547 b: 160000 81920 swap # (Cyl. 84* - 218*) 548 c: 1173930 0 unused 0 0 # (Cyl. 0 - 1211*) 549 h: 962010 211920 vinum # (Cyl. 218*- 1211*) 550.Ed 551.Pp 552Lines starting with a # mark are comments. Most of the other specifications are 553no longer used. The ones which must still be set correctly are: 554.Pp 555.Bl -hang -width 20n 556.It Nm label 557is an optional label, set by the 558.Ar packid 559option when writing a label. 560.It Nm flags 561Flags may be 562.Ar removable , 563.Ar ecc 564or 565.Ar badsect . 566.Ar removable 567is set for removable media drives, but no current 568.Fx 569driver evaluates this 570flag. 571.Ar ecc 572is no longer supported; 573.Ar badsect 574specifies that the drive can perform bad sector remapping. 575.It Nm sectors/unit 576describes the total size of the disk. This value must be correct. 577.It Nm the partition table 578This is the 579.Ux 580partition table, not the Microsoft partition table described in 581.Xr fdisk 8 . 582.El 583.Pp 584The partition table can have up to 8 entries. It contains the following 585information: 586.Bl -hang -width 10n 587.It identifier 588The partition identifier is a single letter in the range 589.Dq a 590to 591.Dq h . 592By convention, partition 593.Dq c 594is reserved to describe the entire disk. 595.It size 596is the size of the partition in sectors, 597.Cm K 598(kilobytes - 1024), 599.Cm M 600(megabytes - 1024*1024), 601.Cm G 602(gigabytes - 1024*1024*1024), 603.Cm % 604(percentage of free space AFTER removing any fixed-size partitions other 605than partition 606.Dq c) , 607or 608.Cm * 609(all remaining free space AFTER fixed-size and percentage 610partitions). For partition 611.Dq c , 612a size of 613.Cm * 614indicates the entire disk. Lowercase versions of 615.Cm K , M , 616and 617.Cm G 618are allowed. 619Size and type should be specifed without any spaces between them. 620.Pp 621Example: 2097152, 1g, 1024m and 1048576k are all the same size 622(assuming 512-byte sectors). 623.It offset 624is the offset of the start of the partition from the beginning of the 625drive in sectors, or 626.Cm * 627to have 628.Nm 629calculate the correct offset to use (the end of the previous partition plus 630one, ignoring partition 631.Dq c . 632For partition 633.Dq c , 634.Cm * 635will be interpreted as an offset of 0. 636.It fstype 637describes the purpose of the partition. The example shows all currently used 638partition types. 639For UFS file systems and ccd partitions, use type 640.Cm 4.2BSD . 641For Vinum drives, use type 642.Cm vinum . 643Other common types are 644.Cm unused 645and 646.Cm swap . 647By convention, partition 648.Dq c 649represents the entire slice and should be of type 650.Cm unused , 651though 652.Nm 653does not enforce this convention. 654The 655.Nm 656utility 657also knows about a number of other partition types, none of which are in current 658use. 659See the definitions starting with 660.Dv FS_UNUSED 661in 662.Pa /usr/include/sys/disklabel.h 663for more details. 664.It fsize 665For 666.Cm 4.2BSD 667and LFS file systems only, the fragment size. Defaults to 1024 for 668partitions smaller than 1 GB, 4096 for partitions 1GB or larger. 669.It bsize 670For 671.Cm 4.2BSD 672and LFS file systems only, the block size. Defaults to 8192 for 673partitions smaller than 1 GB, 16384 for partitions 1GB or larger. 674.It bps/cpg 675For 676.Cm 4.2BSD 677file systems, the number of cylinders in a cylinder group. For LFS file 678systems, the segment shift value. Defaults to 16 for 679partitions smaller than 1 GB, 64 for partitions 1GB or larger. 680.El 681.Pp 682The remainder of the line is a comment and shows the cylinder allocations based 683on the obsolete (but possibly correct) geometry information about the drive. 684The asterisk (*) indicates that the partition does not begin or end exactly on a 685cylinder boundary. 686.Sh EXAMPLES 687.Dl disklabel da0 688.Pp 689Display the in-core label for 690.Pa da0s1 691as obtained via 692.Pa /dev/da0s1 . 693When reading a label, 694.Fx 695will allow you to specify the base disk name 696even if the label resides on a slice. However, to be proper you should 697specify the base disk name only if you are using a 698.Dq dangerously-dedicated 699label. Normally you specify the slice. 700.Pp 701.Dl disklabel da0s1 > savedlabel 702.Pp 703Save the in-core label for 704.Pa da0s1 705into the file 706.Pa savedlabel . 707This file can be used with the 708.Fl R 709flag to restore the label at a later date. 710.Pp 711.Dl disklabel -w -r /dev/da0s1 da2212 foo 712.Pp 713Create a label for 714.Pa da0s1 715based on information for 716.Dq da2212 717found in 718.Pa /etc/disktab . 719Any existing bootstrap code will be clobbered. 720.Pp 721.Dl disklabel -e -r da0s1 722.Pp 723Read the on-disk label for 724.Pa da0s1 , 725edit it and reinstall in-core as well as on-disk. Existing bootstrap code is 726unaffected. 727.Pp 728.Dl disklabel -e -r -n da0s1 729.Pp 730Read the on-disk label for 731.Pa da0s1 , 732edit it, and display what the new label would be (in sectors). It does 733NOT install the new label either in-core or on-disk. 734.Pp 735.Dl disklabel -r -w da0s1 auto 736.Pp 737Try to auto-detect the required information from 738.Pa da0s1 , 739and write a new label to the disk. Use another disklabel -e command to edit the 740partitioning and file system information. 741.Pp 742.Dl disklabel -R da0s1 savedlabel 743.Pp 744Restore the on-disk and in-core label for 745.Pa da0s1 746from information in 747.Pa savedlabel . 748Existing bootstrap code is unaffected. 749.Pp 750.Dl disklabel -R -n da0s1 label_layout 751.Pp 752Display what the label would be for 753.Pa da0s1 754using the partition layout in 755.Pa label_layout . 756This is useful for determining how much space would be alloted for various 757partitions with a labelling scheme using 758.Cm % Ns -based 759or 760.Cm * 761partition sizes. 762.Pp 763.Dl disklabel -B da0s1 764.Pp 765Install a new bootstrap on 766.Pa da0s1 . 767The boot code comes from 768.Pa /boot/boot1 769and possibly 770.Pa /boot/boot2 . 771On-disk and in-core labels are unchanged. 772.Pp 773.Dl disklabel -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212 774.Pp 775Install a new label and bootstrap. 776The label is derived from disktab information for 777.Dq da2212 778and installed both in-core and on-disk. 779The bootstrap code comes from the files 780.Pa /boot/newboot1 781and 782.Pa /boot/newboot2 . 783.Pp 784.Dl dd if=/dev/zero of=/dev/da0 bs=512 count=32 785.Dl fdisk -BI da0 786.Dl dd if=/dev/zero of=/dev/da0s1 bs=512 count=32 787.Dl disklabel -w -B da0s1 auto 788.Dl disklabel -e da0s1 789.Pp 790Completely wipe any prior information on the disk, creating a new bootable 791disk with a DOS partition table containing one 792.Dq whole-disk 793slice. Then 794initialize the slice, then edit it to your needs. The 795.Pa dd 796commands are optional, but may be necessary for some BIOSes to properly 797recognize the disk. 798.Pp 799This is an example disklabel that uses some of the new partition size types 800such as 801.Cm % , M , G , 802and 803.Cm * , 804which could be used as a source file for 805.Pp 806.Dl disklabel -R ad0s1c new_label_file 807.Bd -literal -offset 4n 808# /dev/ad0s1c: 809type: ESDI 810disk: ad0s1 811label: 812flags: 813bytes/sector: 512 814sectors/track: 63 815tracks/cylinder: 16 816sectors/cylinder: 1008 817cylinders: 40633 818sectors/unit: 40959009 819rpm: 3600 820interleave: 1 821trackskew: 0 822cylinderskew: 0 823headswitch: 0 # milliseconds 824track-to-track seek: 0 # milliseconds 825drivedata: 0 826 8278 partitions: 828# size offset fstype [fsize bsize bps/cpg] 829 a: 400M 0 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*) 830 b: 1G * swap 831 c: * * unused 832 e: 204800 * 4.2BSD 833 f: 5g * 4.2BSD 834 g: * * 4.2BSD 835.Ed 836.Sh SEE ALSO 837.Xr ccd 4 , 838.Xr disklabel 5 , 839.Xr disktab 5 , 840.Xr boot0cfg 8 , 841.Xr fdisk 8 , 842.Xr vinum 8 843.Sh DIAGNOSTICS 844The kernel device drivers will not allow the size of a disk partition 845to be decreased or the offset of a partition to be changed while it is open. 846Some device drivers create a label containing only a single large partition 847if a disk is unlabeled; thus, the label must be written to the 848.Dq a 849partition of the disk while it is open. This sometimes requires the desired 850label to be set in two steps, the first one creating at least one other 851partition, and the second setting the label on the new partition while shrinking 852the 853.Dq a 854partition. 855.Pp 856On some machines the bootstrap code may not fit entirely in the area 857allocated for it by some file systems. 858As a result, it may not be possible to have file systems on some partitions 859of a 860.Dq bootable 861disk. 862When installing bootstrap code, 863.Nm 864checks for these cases. 865If the installed boot code would overlap a partition of type FS_UNUSED 866it is marked as type FS_BOOT. 867The 868.Xr newfs 8 869utility will disallow creation of file systems on FS_BOOT partitions. 870Conversely, if a partition has a type other than FS_UNUSED or FS_BOOT, 871.Nm 872will not install bootstrap code that overlaps it. 873.Sh BUGS 874When a disk name is given without a full pathname, 875the constructed device name uses the 876.Dq c 877partition. 878.Pp 879For the i386 architecture, the primary bootstrap sector contains 880an embedded 881.Em fdisk 882table. 883The 884.Nm 885utility takes care to not clobber it when installing a bootstrap only 886.Pq Fl B , 887or when editing an existing label 888.Pq Fl e , 889but it unconditionally writes the primary bootstrap program onto 890the disk for 891.Fl w 892or 893.Fl R , 894thus replacing the 895.Em fdisk 896table by the dummy one in the bootstrap program. This is only of 897concern if the disk is fully dedicated, so that the 898.Bx 899disklabel 900starts at absolute block 0 on the disk. 901.Pp 902The 903.Nm 904utility 905does not perform all possible error checking. Warning *is* given if partitions 906overlap; if an absolute offset does not match the expected offset; if the 907.Dq c 908partition does not start at 0 or does not cover the entire slice; if a 909partition runs past the end of the device; and a number of other errors; but 910no warning is given if space remains unused. 911