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 FreeBSD 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 97.Nm Disklabel 98installs, examines or modifies the label on a disk drive or pack. When writing 99the label, it can be used to change the drive identification, the disk 100partitions on the drive, or to replace a damaged label. There are several forms 101of the command that read (display), install or edit the label on a disk. In 102addition, 103.Nm 104can install bootstrap code. 105.Ss Raw or in-core label 106.Pp 107The disk label is resident close to or at the beginning of each disk partition. 108For faster access, the kernel maintains a copy in core at all times. By 109default, most 110.Nm 111access the in-core copy of the label. To access the raw (on-disk) copy, use the 112.Fl r 113option. This option allows a label to be installed on a disk without kernel 114support for a label, such as when labels are first installed on a system; it 115must be used when first installing a label on a disk. The specific effect of 116.Fl r 117is described under each command. 118.Pp 119.Ss Disk device name 120.Pp 121All 122.Nm 123forms require a disk device name, which should always be the raw 124device name representing the disk or slice. For example 125.Pa da0 126represents the entire disk irregardless of any DOS partitioning, 127and 128.Pa da0s1 129represents a slice. Some devices, most notably 130.Ar ccd , 131require that the 132.Dq whole-disk 133(or 134.Dq c ) 135partition be specified. For example 136.Pa ccd0c . 137You do not have to include the 138.Pa /dev/ 139path prefix when specifying the device. 140.Nm 141will automatically prepend it. 142.Ss Reading the disk label 143.Pp 144To examine or save the label on a disk drive, use 145.Nm 146without options: 147.Pp 148.Nm 149.Op Fl r 150.Ar disk 151.Pp 152.Ar disk 153represents the raw disk in question, and may be in the form 154.Pa da0 155or 156.Pa /dev/da0c . 157It will display all of the parameters associated with the drive and its 158partition layout. Unless the 159.Fl r 160flag is given, 161the kernel's in-core copy of the label is displayed; 162if the disk has no label, or the partition types on the disk are incorrect, 163the kernel may have constructed or modified the label. 164If the 165.Fl r 166flag is given, 167.Nm 168reads the label from the raw disk and displays it. Both versions are usually 169identical except in the case where a label has not yet been initialized or 170is corrupt. 171.Ss Writing a standard label 172.Pp 173To write a standard label, use the form 174.Pp 175.Nm 176.Fl w 177.Op Fl r 178.Op Fl n 179.Ar disk Ar disktype/auto 180.Oo Ar packid Oc 181.Pp 182.Nm 183.Fl w 184.Op Fl r 185.Op Fl n 186.Ar disk 187auto 188.Pp 189The required arguments to 190.Nm 191are the drive to be labeled and the drive type as described in the 192.Xr disktab 5 193file. The drive parameters and partitions are taken from that file. If 194different disks of the same physical type are to have different partitions, it 195will be necessary to have separate disktab entries describing each, or to edit 196the label after installation as described below. The optional argument is a 197pack identification string, up to 16 characters long. The pack id must be 198quoted if it contains blanks. 199.Pp 200If the 201.Fl n 202flag is given, no data will be written to the device, and instead the 203disklabel that would have been written will be printed to stdout. 204.Pp 205If the 206.Fl r 207flag is given, the disk sectors containing the label and bootstrap 208will be written directly. 209A side-effect of this is that any existing bootstrap code will be overwritten 210and the disk rendered unbootable. See the boot options below for a method of 211writing the label and the bootstrap at the same time. 212If 213.Fl r 214is not specified, 215the existing label will be updated via the in-core copy and any bootstrap 216code will be unaffected. 217If the disk does not already have a label, the 218.Fl r 219flag must be used. 220In either case, the kernel's in-core label is replaced. 221.Pp 222For a virgin disk that is not known to 223.Xr disktab 5 , 224.Ar disktype 225can be specified as 226.Dq auto . 227In this case, the driver is requested to produce a virgin label for the 228disk. This might or might not be successful, depending on whether the 229driver for the disk is able to get the required data without reading 230anything from the disk at all. It will likely succeed for all SCSI 231disks, most IDE disks, and vnode devices. Writing a label to the 232disk is the only supported operation, and the 233.Ar disk 234itself must be provided as the canonical name, i.e. not as a full 235path name. 236.Pp 237For most harddisks, a label based on percentages for most partitions (and 238one partition with a size of 239.Ql * ) 240will produce a reasonable configuration. 241.Pp 242PC-based systems have special requirements in order for the BIOS to properly 243recognize a 244.Fx 245disklabel. Older systems may require what is known as a 246.Dq dangerously dedicated 247disklabel, which creates a fake DOS partition to work around problems older 248BIOSes have with modern disk geometries. On newer systems you generally want 249to create a normal DOS slice using 250.Ar fdisk 251and then create a 252.Fx 253disklabel within that slice. This is described 254later on in this page. 255.Pp 256Installing a new disklabel does not in of itself allow your system to boot 257a kernel using that label. You must also install boot blocks, which is 258described later on in this manual page. 259.Ss Editing an existing disk label 260.Pp 261To edit an existing disk label, use the form 262.Pp 263.Nm 264.Fl e 265.Op Fl r 266.Op Fl n 267.Ar disk 268.Pp 269This command reads the label from the in-core kernel copy, or directly from the 270disk if the 271.Fl r 272flag is also specified. The label is written to a file in ASCII and then 273supplied to an editor for changes. If no editor is specified in an 274.Ev EDITOR 275environment variable, 276.Xr vi 1 277is used. When the editor terminates, the label file is used to rewrite the disk 278label. Existing bootstrap code is unchanged regardless of whether 279.Fl r 280was specified. If 281.Fl n 282is specified, no data will be written to the device, and instead the 283disklabel that would have been written will be printed to stdout. This is 284useful to see how a partitioning scheme will work out for a specific disk. 285.Ss Restoring a disk label from a file 286.Pp 287To restore a disk label from a file, use the form 288.Pp 289.Nm 290.Fl R 291.Op Fl r 292.Op Fl n 293.Ar disk Ar protofile 294.Pp 295.Nm 296is capable of restoring a disk label that was previously saved in a file in ASCII format. 297The prototype file used to create the label should be in the same format as that 298produced when reading or editing a label. Comments are delimited by 299.Ar \&# 300and newline. As when writing a new label, any existing bootstrap code will be 301clobbered if 302.Fl r 303is specified and will be unaffected otherwise. See the boot options below for a 304method of restoring the label and writing the bootstrap at the same time. 305If 306.Fl n 307is used, no data will be written to the device, and instead the 308disklabel that would have been written will be printed to stdout. This is 309useful to see how a partitioning scheme will work out for a specific disk. 310.Ss Enabling and disabling writing to the disk label area 311.Pp 312By default, it is not possible to write to the disk label area at the beginning 313of a disk. The disk driver silently ignores any attempt to do so. If you need 314to write to this area (for example, to obliterate the label), use the form 315.Pp 316.Nm 317.Op Fl W 318.Ar disk 319.Pp 320To disallow writing to the label area after previously allowing it, use the 321command 322.Pp 323.Nm 324.Op Fl N 325.Ar disk 326.Ss Installing bootstraps 327.Pp 328The final three forms of 329.Nm 330are used to install bootstrap code. If you are creating a 331.Dq dangerously-dedicated 332partition for compatibility with older PC systems, 333you generally want to specify the raw disk name such as 334.Pa da0 . 335If you are creating a label within an existing DOS slice, you should specify 336the slice name such as 337.Pa da0s1 . 338Making a partition bootable can be tricky. If you are using a normal DOS 339slice you typically install (or leave) a standard MBR on the base disk and 340then install the 341.Fx 342bootblocks in the slice. 343.Pp 344.Nm 345.Fl B 346.Oo 347.Fl b Ar boot1 348.Fl s Ar boot2 349.Oc 350.Ar disk 351.Oo Ar disktype Oc 352.Pp 353This form installs the bootstrap only. It does not change the disk label. 354You should never use this command on a base disk unless you intend to create a 355.Dq dangerously-dedicated 356disk, such as 357.Ar da0 . 358This command is typically run on a slice such as 359.Ar da0s1 . 360.Pp 361.Nm 362.Fl w 363.Fl B 364.Op Fl n 365.Oo 366.Fl b Ar boot1 367.Fl s Ar boot2 368.Oc 369.Ar disk Ar disktype 370.Oo Ar packid Oc 371.Pp 372This form corresponds to the 373.Dq write label 374command described above. 375In addition to writing a new volume label, it also installs the bootstrap. 376If run on a base disk this command will create a 377.Dq dangerously-dedicated 378label. This command is normally run on a slice rather than a base disk. 379If 380.Fl n 381is used, no data will be written to the device, and instead the 382disklabel that would have been written will be printed to stdout. 383.Pp 384.Nm 385.Fl R 386.Fl B 387.Op Fl n 388.Oo 389.Fl b Ar boot1 390.Fl s Ar boot2 391.Oc 392.Ar disk Ar protofile 393.Oo Ar disktype Oc 394.Pp 395This form corresponds to the 396.Dq restore label 397command described above. 398In addition to restoring the volume label, it also installs the bootstrap. 399If run on a base disk this command will create a 400.Dq dangerously-dedicated 401label. This command is normally run on a slice rather than a base disk. 402.Pp 403The bootstrap commands always access the disk directly, so it is not necessary 404to specify the 405.Fl r 406flag. If 407.Fl n 408is used, no data will be written to the device, and instead the 409disklabel that would have been written will be printed to stdout. 410.Pp 411The bootstrap code is comprised of two boot programs. Specify the name of the 412boot programs to be installed in one of these ways: 413.Bl -enum 414.It 415Specify the names explicitly with the 416.Fl b 417and 418.Fl s 419flags. 420.Fl b 421indicates the primary boot program and 422.Fl s 423the secondary boot program. The boot programs are located in 424.Pa /boot . 425.It 426If the 427.Fl b 428and 429.Fl s 430flags are not specified, but 431.Ar disktype 432was specified, the names of the programs are taken from the 433.Dq b0 434and 435.Dq b1 436parameters of the 437.Xr disktab 5 438entry for the disk if the disktab entry exists and includes those parameters. 439.It 440Otherwise, the default boot image names are used: 441.Pa /boot/boot1 442and 443.Pa /boot/boot2 444for the standard stage1 and stage2 boot images (details may vary 445on architectures like the Alpha, where only a single-stage boot is used). 446.El 447.Ss Initializing/Formatting a bootable disk from scratch 448.Pp 449To initialize a disk from scratch the following sequence is recommended. 450Please note that this will wipe everything that was previously on the disk, 451including any 452.No non- Ns Fx 453slices. 454.Bl -enum 455.It 456Use 457.Ar fdisk 458to initialize the DOS partition table, creating a real whole-disk slice to 459hold the 460.Fx 461disklabel, and installing a master boot record. 462.It 463Use 464.Ar disklabel 465to initialize a virgin 466.Fx 467disklabel and install 468.Fx 469boot blocks. 470.It 471Use 472.Ar disklabel 473to edit your newly created label, adding appropriate partitions. 474.It 475Finally newfs the filesystem partitions you created in the label. A typical 476disklabel partitioning scheme would be to have an 477.Dq a 478partition 479of approximately 128MB to hold the root filesystem, a 480.Dq b 481partition for 482swap, a 483.Dq d 484partition for /var (usually 128MB), an 485.Dq e 486partition 487for /var/tmp (usually 128MB), an 488.Dq f 489partition for /usr (usually around 2G), 490and finally a 491.Dq g 492partition for /home (usually all remaining space). 493Your mileage may vary. 494.El 495.Pp 496.Nm fdisk Fl BI Ar da0 497.Pp 498.Nm 499.Fl w 500.Fl r 501.Fl B 502.Ar da0s1 503auto 504.Pp 505.Pp 506.Nm 507.Fl e 508.Ar da0s1 509.Pp 510.Sh FILES 511.Bl -tag -width Pa -compact 512.It Pa /etc/disktab 513.It Pa /boot/ 514.It Pa /boot/boot<n> 515.El 516.Sh SAVED FILE FORMAT 517.Nm 518uses an ASCII version of the label when examining, editing or restoring a disk 519label. The format is: 520.Bd -literal -offset 4n 521# /dev/da1c: 522type: SCSI 523disk: da0s1 524label: 525flags: 526bytes/sector: 512 527sectors/track: 51 528tracks/cylinder: 19 529sectors/cylinder: 969 530cylinders: 1211 531sectors/unit: 1173930 532rpm: 3600 533interleave: 1 534trackskew: 0 535cylinderskew: 0 536headswitch: 0 # milliseconds 537track-to-track seek: 0 # milliseconds 538drivedata: 0 539 5408 partitions: 541# size offset fstype [fsize bsize bps/cpg] 542 a: 81920 0 4.2BSD 1024 8192 16 # (Cyl. 0 - 84*) 543 b: 160000 81920 swap # (Cyl. 84* - 218*) 544 c: 1173930 0 unused 0 0 # (Cyl. 0 - 1211*) 545 h: 962010 211920 vinum # (Cyl. 218*- 1211*) 546.Ed 547.Pp 548Lines starting with a # mark are comments. Most of the other specifications are 549no longer used. The ones which must still be set correctly are: 550.Pp 551.Bl -hang -width 20n 552.It Nm label 553is an optional label, set by the 554.Ar packid 555option when writing a label. 556.It Nm flags 557Flags may be 558.Ar removable , 559.Ar ecc 560or 561.Ar badsect . 562.Ar removable 563is set for removable media drives, but no current 564.Fx 565driver evaluates this 566flag. 567.Ar ecc 568is no longer supported; 569.Ar badsect 570specifies that the drive can perform bad sector remapping. 571.It Nm sectors/unit 572describes the total size of the disk. This value must be correct. 573.It Nm the partition table 574This is the 575.Ux 576partition table, not the Microsoft partition table described in 577.Xr fdisk 8 . 578.El 579.Pp 580The partition table can have up to 8 entries. It contains the following 581information: 582.Bl -hang -width 10n 583.It identifier 584The partition identifier is a single letter in the range 585.Dq a 586to 587.Dq h . 588By convention, partition 589.Dq c 590is reserved to describe the entire disk. 591.It size 592is the size of the partition in sectors, 593.Cm K 594(kilobytes - 1024), 595.Cm M 596(megabytes - 1024*1024), 597.Cm G 598(gigabytes - 1024*1024*1024), 599.Cm % 600(percentage of free space AFTER removing any fixed-size partitions other 601than partition 602.Dq c) , 603or 604.Cm * 605(all remaining free space AFTER fixed-size and percentage 606partitions). For partition 607.Dq c , 608a size of 609.Cm * 610indicates the entire disk. Lowercase versions of 611.Cm K , M , 612and 613.Cm G 614are allowed. 615Size and type should be specifed without any spaces between them. 616.Pp 617Example: 2097152, 1g, 1024m and 1048576k are all the same size 618(assuming 512-byte sectors). 619.It offset 620is the offset of the start of the partition from the beginning of the 621drive in sectors, or 622.Cm * 623to have 624.Nm 625calculate the correct offset to use (the end of the previous partition plus 626one, ignoring partition 627.Dq c . 628For partition 629.Dq c , 630.Cm * 631will be interpreted as an offset of 0. 632.It fstype 633describes the purpose of the partition. The example shows all currently used 634partition types. 635For UFS file systems and ccd partitions, use type 636.Cm 4.2BSD . 637For Vinum drives, use type 638.Cm vinum . 639Other common types are 640.Cm unused 641and 642.Cm swap . 643By convention, partition 644.Dq c 645represents the entire slice and should be of type 646.Cm unused , 647though 648.Nm 649does not enforce this convention. 650.Nm 651also knows about a number of other partition types, none of which are in current 652use. 653See the definitions starting with 654.Dv FS_UNUSED 655in 656.Pa /usr/include/sys/disklabel.h 657for more details. 658.It fsize 659For 660.Cm 4.2BSD 661and LFS file systems only, the fragment size. Defaults to 8192 for 662partitions smaller than 1 GB, 16384 for partitions 1GB or larger. 663.It bsize 664For 665.Cm 4.2BSD 666and LFS file systems only, the block size. Defaults to 1024 for 667partitions smaller than 1 GB, 4096 for partitions 1GB or larger. 668.It bps/cpg 669For 670.Cm 4.2BSD 671file systems, the number of cylinders in a cylinder group. For LFS file 672systems, the segment shift value. Defaults to 16 for 673partitions smaller than 1 GB, 64 for partitions 1GB or larger. 674.El 675.Pp 676The remainder of the line is a comment and shows the cylinder allocations based 677on the obsolete (but possibly correct) geometry information about the drive. 678The asterisk (*) indicates that the partition does not begin or end exactly on a 679cylinder boundary. 680.Sh EXAMPLES 681.Dl disklabel da0 682.Pp 683Display the in-core label for 684.Pa da0s1 685as obtained via 686.Pa /dev/da0s1 . 687When reading a label, 688.Fx 689will allow you to specify the base disk name 690even if the label resides on a slice. However, to be proper you should 691specify the base disk name only if you are using a 692.Dq dangerously-dedicated 693label. Normally you specify the slice. 694.Pp 695.Dl disklabel da0s1 > savedlabel 696.Pp 697Save the in-core label for 698.Pa da0s1 699into the file 700.Pa savedlabel . 701This file can be used with the 702.Fl R 703flag to restore the label at a later date. 704.Pp 705.Dl disklabel -w -r /dev/da0s1 da2212 foo 706.Pp 707Create a label for 708.Pa da0s1 709based on information for 710.Dq da2212 711found in 712.Pa /etc/disktab . 713Any existing bootstrap code will be clobbered. 714.Pp 715.Dl disklabel -e -r da0s1 716.Pp 717Read the on-disk label for 718.Pa da0s1 , 719edit it and reinstall in-core as well as on-disk. Existing bootstrap code is 720unaffected. 721.Pp 722.Dl disklabel -e -r -n da0s1 723.Pp 724Read the on-disk label for 725.Pa da0s1 , 726edit it, and display what the new label would be (in sectors). It does 727NOT install the new label either in-core or on-disk. 728.Pp 729.Dl disklabel -r -w da0s1 auto 730.Pp 731Try to auto-detect the required information from 732.Pa da0s1 , 733and write a new label to the disk. Use another disklabel -e command to edit the 734partitioning and file system information. 735.Pp 736.Dl disklabel -R da0s1 savedlabel 737.Pp 738Restore the on-disk and in-core label for 739.Pa da0s1 740from information in 741.Pa savedlabel . 742Existing bootstrap code is unaffected. 743.Pp 744.Dl disklabel -R -n da0s1 label_layout 745.Pp 746Display what the label would be for 747.Pa da0s1 748using the partition layout in 749.Pa label_layout . 750This is useful for determining how much space would be alloted for various 751partitions with a labelling scheme using 752.Cm % Ns -based 753or 754.Cm * 755partition sizes. 756.Pp 757.Dl disklabel -B da0s1 758.Pp 759Install a new bootstrap on 760.Pa da0s1 . 761The boot code comes from 762.Pa /boot/boot1 763and possibly 764.Pa /boot/boot2 . 765On-disk and in-core labels are unchanged. 766.Pp 767.Dl disklabel -w -B /dev/da0s1 -b newboot1 -s newboot da2212 768.Pp 769Install a new label and bootstrap. 770The label is derived from disktab information for 771.Dq da2212 772and installed both in-core and on-disk. 773The bootstrap code comes from the files 774.Pa /boot/newboot1 775and 776.Pa /boot/newboot2 . 777.Pp 778.Dl dd if=/dev/zero of=/dev/da0 bs=512 count=32 779.Dl fdisk -BI da0 780.Dl dd if=/dev/zero of=/dev/da0s1 bs=512 count=32 781.Dl disklabel -w -r -B da0s1 auto 782.Dl disklabel -e da0s1 783.Pp 784Completely wipe any prior information on the disk, creating a new bootable 785disk with a DOS partition table containing one 786.Dq whole-disk 787slice. Then 788initialize the slice, then edit it to your needs. The 789.Pa dd 790commands are optional, but may be necessary for some BIOSes to properly 791recognize the disk. 792.Pp 793This is an example disklabel that uses some of the new partition size types 794such as 795.Cm % , M , G , 796and 797.Cm * , 798which could be used as a source file for 799.Pp 800.Dl disklabel -R ad0s1c new_label_file 801.Bd -literal -offset 4n 802# /dev/ad0s1c: 803type: ESDI 804disk: ad0s1 805label: 806flags: 807bytes/sector: 512 808sectors/track: 63 809tracks/cylinder: 16 810sectors/cylinder: 1008 811cylinders: 40633 812sectors/unit: 40959009 813rpm: 3600 814interleave: 1 815trackskew: 0 816cylinderskew: 0 817headswitch: 0 # milliseconds 818track-to-track seek: 0 # milliseconds 819drivedata: 0 820 8218 partitions: 822# size offset fstype [fsize bsize bps/cpg] 823 a: 400M 0 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*) 824 b: 1G * swap 825 c: * * unused 826 e: 204800 * 4.2BSD 827 f: 5g * 4.2BSD 828 g: * * 4.2BSD 829.Ed 830.Sh SEE ALSO 831.Xr ccd 4 , 832.Xr disklabel 5 , 833.Xr disktab 5 , 834.Xr boot0cfg 8 , 835.Xr fdisk 8 , 836.Xr vinum 8 837.Sh DIAGNOSTICS 838The kernel device drivers will not allow the size of a disk partition 839to be decreased or the offset of a partition to be changed while it is open. 840Some device drivers create a label containing only a single large partition 841if a disk is unlabeled; thus, the label must be written to the 842.Dq a 843partition of the disk while it is open. This sometimes requires the desired 844label to be set in two steps, the first one creating at least one other 845partition, and the second setting the label on the new partition while shrinking 846the 847.Dq a 848partition. 849.Pp 850On some machines the bootstrap code may not fit entirely in the area 851allocated for it by some filesystems. 852As a result, it may not be possible to have filesystems on some partitions 853of a 854.Dq bootable 855disk. 856When installing bootstrap code, 857.Nm 858checks for these cases. 859If the installed boot code would overlap a partition of type FS_UNUSED 860it is marked as type FS_BOOT. 861The 862.Xr newfs 8 863utility will disallow creation of filesystems on FS_BOOT partitions. 864Conversely, if a partition has a type other than FS_UNUSED or FS_BOOT, 865.Nm 866will not install bootstrap code that overlaps it. 867.Sh BUGS 868When a disk name is given without a full pathname, 869the constructed device name uses the 870.Dq c 871partition. 872.Pp 873For the i386 architecture, the primary bootstrap sector contains 874an embedded 875.Em fdisk 876table. 877.Nm Disklabel 878takes care to not clobber it when installing a bootstrap only 879.Pq Fl B , 880or when editing an existing label 881.Pq Fl e , 882but it unconditionally writes the primary bootstrap program onto 883the disk for 884.Fl w 885or 886.Fl R , 887thus replacing the 888.Em fdisk 889table by the dummy one in the bootstrap program. This is only of 890concern if the disk is fully dedicated, so that the BSD disklabel 891starts at absolute block 0 on the disk. 892.Pp 893.Nm 894does not perform all possible error checking. Warning *is* given if partitions 895overlap; if an absolute offset does not match the expected offset; if the 896.Dq c 897partition does not start at 0 or does not cover the entire slice; if a 898partition runs past the end of the device; and a number of other errors; but 899no warning is given if space remains unused. 900