1 .\" Copyright (c) 1987, 1988, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" This code is derived from software contributed to Berkeley by
5 .\" Symmetric Computer Systems.
7 .\" Redistribution and use in source and binary forms, with or without
8 .\" modification, are permitted provided that the following conditions
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.
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
35 .\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94
36 .\" $FreeBSD: src/sbin/disklabel/disklabel.8,v 1.15.2.22 2003/04/17 17:56:34 trhodes Exp $
37 .\" $DragonFly: src/sbin/disklabel/disklabel.8,v 1.2 2003/06/17 04:27:32 dillon Exp $
44 .Nd read and write disk pack label
53 .Ar disk Ar disktype/auto
76 .Oo Ar disktype/auto Oc
85 .Ar disk Ar disktype/auto
96 .Oo Ar disktype/auto Oc
101 installs, examines or modifies the label on a disk drive or pack. When writing
102 the label, it can be used to change the drive identification, the disk
103 partitions on the drive, or to replace a damaged label. There are several forms
104 of the command that read (display), install or edit the label on a disk. In
107 can install bootstrap code.
108 .Ss Raw or in-core label
110 The disk label resides close to or at the beginning of each disk slice.
111 For faster access, the kernel maintains a copy in core at all times. By
114 access the in-core copy of the label. To access the raw (on-disk) copy, use the
116 option. This option allows a label to be installed on a disk without kernel
117 support for a label, such as when labels are first installed on a system; it
118 must be used when first installing a label on a disk. The specific effect of
120 is described under each command.
126 forms require a disk device name, which should always be the raw
127 device name representing the disk or slice. For example
129 represents the entire disk regardless of any DOS partitioning,
132 represents a slice. Some devices, most notably
138 partition be specified. For example
140 You do not have to include the
142 path prefix when specifying the device.
145 utility will automatically prepend it.
146 .Ss Reading the disk label
148 To examine the label on a disk drive, use
157 represents the raw disk in question, and may be in the form
161 It will display all of the parameters associated with the drive and its
162 partition layout. Unless the
165 the kernel's in-core copy of the label is displayed;
166 if the disk has no label, or the partition types on the disk are incorrect,
167 the kernel may have constructed or modified the label.
172 reads the label from the raw disk and displays it. Both versions are usually
173 identical except in the case where a label has not yet been initialized or
175 .Ss Writing a standard label
177 To write a standard label, use the form
183 .Ar disk Ar disktype/auto
193 The required arguments to
195 are the drive to be labeled and the drive type as described in the
197 file. The drive parameters and partitions are taken from that file. If
198 different disks of the same physical type are to have different partitions, it
199 will be necessary to have separate disktab entries describing each, or to edit
200 the label after installation as described below. The optional argument is a
201 pack identification string, up to 16 characters long. The pack id must be
202 quoted if it contains blanks.
206 flag is given, no data will be written to the device, and instead the
207 disklabel that would have been written will be printed to stdout.
211 flag is given, the disk sectors containing the label and bootstrap
212 will be written directly.
213 A side-effect of this is that any existing bootstrap code will be overwritten
214 and the disk rendered unbootable. See the boot options below for a method of
215 writing the label and the bootstrap at the same time.
219 the existing label will be updated via the in-core copy and any bootstrap
220 code will be unaffected.
221 If the disk does not already have a label, the
224 In either case, the kernel's in-core label is replaced.
226 For a virgin disk that is not known to
231 In this case, the driver is requested to produce a virgin label for the
232 disk. This might or might not be successful, depending on whether the
233 driver for the disk is able to get the required data without reading
234 anything from the disk at all. It will likely succeed for all SCSI
235 disks, most IDE disks, and vnode devices. Writing a label to the
236 disk is the only supported operation, and the
238 itself must be provided as the canonical name, i.e. not as a full
241 For most harddisks, a label based on percentages for most partitions (and
242 one partition with a size of
244 will produce a reasonable configuration.
246 PC-based systems have special requirements in order for the BIOS to properly
249 disklabel. Older systems may require what is known as a
250 .Dq dangerously dedicated
251 disklabel, which creates a fake DOS partition to work around problems older
252 BIOSes have with modern disk geometries.
253 On newer systems you generally want
254 to create a normal DOS partition using
258 disklabel within that slice. This is described
259 later on in this page.
261 Installing a new disklabel does not in of itself allow your system to boot
262 a kernel using that label. You must also install boot blocks, which is
263 described later on in this manual page.
264 .Ss Editing an existing disk label
266 To edit an existing disk label, use the form
274 This command reads the label from the in-core kernel copy, or directly from the
277 flag is also specified. The label is written to a file in ASCII and then
278 supplied to an editor for changes. If no editor is specified in an
280 environment variable,
282 is used. When the editor terminates, the label file is used to rewrite the disk
283 label. Existing bootstrap code is unchanged regardless of whether
287 is specified, no data will be written to the device, and instead the
288 disklabel that would have been written will be printed to stdout. This is
289 useful to see how a partitioning scheme will work out for a specific disk.
290 .Ss Restoring a disk label from a file
292 To restore a disk label from a file, use the form
298 .Ar disk Ar protofile
301 is capable of restoring a disk label that was previously saved in a file in ASCII format.
302 The prototype file used to create the label should be in the same format as that
303 produced when reading or editing a label. Comments are delimited by
305 and newline. As when writing a new label, any existing bootstrap code will be
308 is specified and will be unaffected otherwise. See the boot options below for a
309 method of restoring the label and writing the bootstrap at the same time.
312 is used, no data will be written to the device, and instead the
313 disklabel that would have been written will be printed to stdout. This is
314 useful to see how a partitioning scheme will work out for a specific disk.
315 .Ss Enabling and disabling writing to the disk label area
317 By default, it is not possible to write to the disk label area at the beginning
318 of a disk. The disk driver arranges for
320 and similar system calls
323 on any attempt to do so. If you need
324 to write to this area (for example, to obliterate the label), use the form
330 To disallow writing to the label area after previously allowing it, use the
336 .Ss Installing bootstraps
338 The final three forms of
340 are used to install bootstrap code. If you are creating a
341 .Dq dangerously-dedicated
342 slice for compatibility with older PC systems,
343 you generally want to specify the raw disk name such as
345 If you are creating a label within an existing DOS slice,
347 the partition name such as
349 Making a slice bootable can be tricky. If you are using a normal DOS
350 slice you typically install (or leave) a standard MBR on the base disk and
353 bootblocks in the slice.
364 This form installs the bootstrap only. It does not change the disk label.
365 You should never use this command on a base disk unless you intend to create a
366 .Dq dangerously-dedicated
369 This command is typically run on a slice such as
383 This form corresponds to the
385 command described above.
386 In addition to writing a new volume label, it also installs the bootstrap.
387 If run on a base disk this command will create a
388 .Dq dangerously-dedicated
389 label. This command is normally run on a slice rather than a base disk.
392 is used, no data will be written to the device, and instead the
393 disklabel that would have been written will be printed to stdout.
403 .Ar disk Ar protofile
406 This form corresponds to the
408 command described above.
409 In addition to restoring the volume label, it also installs the bootstrap.
410 If run on a base disk this command will create a
411 .Dq dangerously-dedicated
412 label. This command is normally run on a slice rather than a base disk.
414 The bootstrap commands always access the disk directly, so it is not necessary
419 is used, no data will be written to the device, and instead the
420 disklabel that would have been written will be printed to stdout.
422 The bootstrap code is comprised of two boot programs. Specify the name of the
423 boot programs to be installed in one of these ways:
426 Specify the names explicitly with the
432 indicates the primary boot program and
434 the secondary boot program. The boot programs are located in
441 flags are not specified, but
443 was specified, the names of the programs are taken from the
449 entry for the disk if the disktab entry exists and includes those parameters.
451 Otherwise, the default boot image names are used:
455 for the standard stage1 and stage2 boot images (details may vary
456 on architectures like the Alpha, where only a single-stage boot is used).
458 .Ss Initializing/Formatting a bootable disk from scratch
460 To initialize a disk from scratch the following sequence is recommended.
461 Please note that this will wipe everything that was previously on the disk,
469 to initialize the hard disk, and create a slice table, referred to
471 .Dq "partition table"
477 to define partitions on
479 slices created in the previous step.
483 to create file systems on new partitions.
486 A typical partitioning scheme would be to have an
489 of approximately 128MB to hold the root file system, a
505 (usually around 2GB),
510 (usually all remaining space).
511 Your mileage may vary.
513 .Nm fdisk Fl BI Pa da0
524 .Bl -tag -width ".Pa /etc/disktab" -compact
528 Disk description file.
530 .Sh SAVED FILE FORMAT
536 version of the label when examining, editing, or restoring a disk
539 .Bd -literal -offset 4n
548 sectors/cylinder: 969
550 sectors/unit: 1173930
555 headswitch: 0 # milliseconds
556 track-to-track seek: 0 # milliseconds
560 # size offset fstype [fsize bsize bps/cpg]
561 a: 81920 0 4.2BSD 1024 8192 16 # (Cyl. 0 - 84*)
562 b: 160000 81920 swap # (Cyl. 84* - 218*)
563 c: 1173930 0 unused 0 0 # (Cyl. 0 - 1211*)
564 h: 962010 211920 vinum # (Cyl. 218*- 1211*)
567 Lines starting with a
570 Most of the other specifications are no longer used.
571 The ones which must still be set correctly are:
575 is an optional label, set by the
577 option when writing a label.
584 is set for removable media drives, but no current
586 driver evaluates this
589 is no longer supported;
591 specifies that the drive can perform bad sector remapping.
593 describes the total size of the disk.
594 This value must be correct.
595 .It Ar "the partition table"
598 partition table, not the
600 partition table described in
604 The partition table can have up to 8 entries.
605 It contains the following information:
606 .Bl -tag -width indent
608 The partition identifier is a single letter in the range
612 By convention, partition
614 is reserved to describe the entire disk.
616 The size of the partition in sectors,
620 (megabytes - 1024*1024),
622 (gigabytes - 1024*1024*1024),
624 (percentage of free space
626 removing any fixed-size partitions other than partition
630 (all remaining free space
632 fixed-size and percentage partitions).
637 indicates the entire disk.
638 Lowercase versions of
643 Size and type should be specifed without any spaces between them.
645 Example: 2097152, 1G, 1024M and 1048576K are all the same size
646 (assuming 512-byte sectors).
648 The offset of the start of the partition from the beginning of the
653 calculate the correct offset to use (the end of the previous partition plus
654 one, ignoring partition
659 will be interpreted as an offset of 0.
661 Describes the purpose of the partition.
662 The example shows all currently used partition types.
669 For Vinum drives, use type
671 Other common types are
675 By convention, partition
677 represents the entire slice and should be of type
681 does not enforce this convention.
685 also knows about a number of other partition types,
686 none of which are in current use.
687 (See the definitions starting with
690 .Aq Pa sys/disklabel.h
697 file systems only, the fragment size.
698 Defaults to 1024 for partitions smaller than 1GB,
699 4096 for partitions 1GB or larger.
705 file systems only, the block size.
706 Defaults to 8192 for partitions smaller than 1GB,
707 16384 for partitions 1GB or larger.
711 file systems, the number of cylinders in a cylinder group.
714 file systems, the segment shift value.
715 Defaults to 16 for partitions smaller than 1GB,
716 64 for partitions 1GB or larger.
719 The remainder of the line is a comment and shows the cylinder allocations based
720 on the obsolete (but possibly correct) geometry information about the drive.
723 indicates that the partition does not begin or end exactly on a
726 .Dl "disklabel da0s1"
728 Display the in-core label for the first slice of the
730 disk, as obtained via
733 .Dq dangerously-dedicated ,
734 the base disk name should be specified, such as
737 .Dl "disklabel da0s1 > savedlabel"
739 Save the in-core label for
743 This file can be used with the
745 option to restore the label at a later date.
747 .Dl "disklabel -w -r /dev/da0s1 da2212 foo"
751 based on information for
755 Any existing bootstrap code will be clobbered
756 and the disk rendered unbootable.
758 .Dl "disklabel -e -r da0s1"
760 Read the on-disk label for
762 edit it, and reinstall in-core as well as on-disk.
763 Existing bootstrap code is unaffected.
765 .Dl "disklabel -e -r -n da0s1"
767 Read the on-disk label for
769 edit it, and display what the new label would be (in sectors).
772 install the new label either in-core or on-disk.
774 .Dl "disklabel -r -w da0s1 auto"
776 Try to auto-detect the required information from
778 and write a new label to the disk.
782 partitioning and file system information.
784 .Dl "disklabel -R da0s1 savedlabel"
786 Restore the on-disk and in-core label for
790 Existing bootstrap code is unaffected.
792 .Dl "disklabel -R -n da0s1 label_layout"
794 Display what the label would be for
796 using the partition layout in
798 This is useful for determining how much space would be alloted for various
799 partitions with a labelling scheme using
805 .Dl disklabel -B da0s1
807 Install a new bootstrap on
809 The boot code comes from
813 On-disk and in-core labels are unchanged.
815 .Dl disklabel -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212
817 Install a new label and bootstrap.
818 The label is derived from disktab information for
820 and installed both in-core and on-disk.
821 The bootstrap code comes from the files
826 .Dl dd if=/dev/zero of=/dev/da0 bs=512 count=32
828 .Dl dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
829 .Dl disklabel -w -B da0s1 auto
830 .Dl disklabel -e da0s1
832 Completely wipe any prior information on the disk, creating a new bootable
833 disk with a DOS partition table containing one
836 initialize the slice, then edit it to your needs. The
838 commands are optional, but may be necessary for some BIOSes to properly
841 This is an example disklabel that uses some of the new partition size types
846 which could be used as a source file for
848 .Dl disklabel -R ad0s1c new_label_file
849 .Bd -literal -offset 4n
858 sectors/cylinder: 1008
860 sectors/unit: 40959009
865 headswitch: 0 # milliseconds
866 track-to-track seek: 0 # milliseconds
870 # size offset fstype [fsize bsize bps/cpg]
871 a: 400M 0 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
886 The kernel device drivers will not allow the size of a disk partition
887 to be decreased or the offset of a partition to be changed while it is open.
888 Some device drivers create a label containing only a single large partition
889 if a disk is unlabeled; thus, the label must be written to the
891 partition of the disk while it is open. This sometimes requires the desired
892 label to be set in two steps, the first one creating at least one other
893 partition, and the second setting the label on the new partition while shrinking
898 On some machines the bootstrap code may not fit entirely in the area
899 allocated for it by some file systems.
900 As a result, it may not be possible to have file systems on some partitions
904 When installing bootstrap code,
906 checks for these cases.
907 If the installed boot code would overlap a partition of type FS_UNUSED
908 it is marked as type FS_BOOT.
911 utility will disallow creation of file systems on FS_BOOT partitions.
912 Conversely, if a partition has a type other than FS_UNUSED or FS_BOOT,
914 will not install bootstrap code that overlaps it.
916 When a disk name is given without a full pathname,
917 the constructed device name uses the
921 For the i386 architecture, the primary bootstrap sector contains
927 utility takes care to not clobber it when installing a bootstrap only
929 or when editing an existing label
931 but it unconditionally writes the primary bootstrap program onto
938 table by the dummy one in the bootstrap program. This is only of
939 concern if the disk is fully dedicated, so that the
942 starts at absolute block 0 on the disk.
947 does not perform all possible error checking. Warning *is* given if partitions
948 overlap; if an absolute offset does not match the expected offset; if the
950 partition does not start at 0 or does not cover the entire slice; if a
951 partition runs past the end of the device; and a number of other errors; but
952 no warning is given if space remains unused.
projects / dragonfly.git / blob