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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 $
43 .Nd read and write 32 bit disk pack label
52 .Ar disk Ar disktype Ns / Ns Cm auto
75 .Oo Ar disktype Ns / Ns Cm auto Oc
84 .Ar disk Ar disktype Ns / Ns Cm auto
95 .Oo Ar disktype Ns / Ns Cm auto Oc
97 .Fl f Ar slice_start_lba
103 installs, examines or modifies a 32 bit label on a disk drive or pack.
105 the label, it can be used to change the drive identification, the disk
106 partitions on the drive, or to replace a damaged label.
107 There are several forms
108 of the command that read (display), install or edit the label on a disk.
112 can install bootstrap code.
113 .Ss Raw or in-core label
114 The disk label resides close to or at the beginning of each disk slice.
115 For faster access, the kernel maintains a copy in core at all times.
117 default, most forms of the
119 command access the in-core copy of the label.
120 To access the raw (on-disk)
124 This option allows a label to be installed on a disk without kernel
125 support for a label, such as when labels are first installed on a system; it
126 must be used when first installing a label on a disk.
127 The specific effect of
129 is described under each command.
133 forms require a disk device name, which should always be the raw
134 device name representing the disk or slice.
136 uses the following scheme for slice numbering:
137 If the disk doesn't use GPT (typically laid out by
139 but e.g.\& MBR (typically laid out by
143 represents the entire disk regardless of any DOS partitioning.
144 Slice 0 is called the compatibility slice,
145 and slice 1 and onward, e.g.\&
150 If the disk does use GPT, then all slices are
152 slices, slice 0 isn't special, it is just the first slice on the disk.
153 You do not have to include the
155 path prefix when specifying the device.
158 utility will automatically prepend it.
159 .Ss Reading the disk label
160 To examine the label on a disk drive, use
169 represents the raw disk in question, and may be in the form
173 It will display all of the parameters associated with the drive and its
178 the kernel's in-core copy of the label is displayed;
179 if the disk has no label, or the partition types on the disk are incorrect,
180 the kernel may have constructed or modified the label.
185 reads the label from the raw disk and displays it.
186 Both versions are usually
187 identical except in the case where a label has not yet been initialized or
189 .Ss Writing a standard label
190 To write a standard label, use the form
196 .Ar disk Ar disktype Ns / Ns Cm auto
199 The required arguments to
201 are the drive to be labeled and the drive type as described in the
204 The drive parameters and partitions are taken from that file.
206 different disks of the same physical type are to have different partitions, it
207 will be necessary to have separate disktab entries describing each, or to edit
208 the label after installation as described below.
209 The optional argument is a
210 pack identification string, up to 16 characters long.
212 quoted if it contains blanks.
216 flag is given, no data will be written to the device, and instead the
217 disklabel that would have been written will be printed to stdout.
221 flag is given, the disk sectors containing the label and bootstrap
222 will be written directly.
223 A side-effect of this is that any existing bootstrap code will be overwritten
224 and the disk rendered unbootable.
225 See the boot options below for a method of
226 writing the label and the bootstrap at the same time.
230 the existing label will be updated via the in-core copy and any bootstrap
231 code will be unaffected.
232 If the disk does not already have a label, the
235 In either case, the kernel's in-core label is replaced.
237 For a virgin disk that is not known to
242 In this case, the driver is requested to produce a virgin label for the
244 This might or might not be successful, depending on whether the
245 driver for the disk is able to get the required data without reading
246 anything from the disk at all.
247 It will likely succeed for all SCSI
248 disks, most IDE disks, and vnode devices.
249 Writing a label to the
250 disk is the only supported operation, and the
252 itself must be provided as the canonical name, i.e.\& not as a full
255 For most harddisks, a label based on percentages for most partitions (and
256 one partition with a size of
258 will produce a reasonable configuration.
260 PC-based systems have special requirements in order for the BIOS to properly
264 Older systems may require what is known as a
265 .Dq dangerously dedicated
266 disklabel, which creates a fake DOS partition to work around problems older
267 BIOSes have with modern disk geometries.
268 On newer systems you generally want
269 to create a normal DOS partition using
273 disklabel within that slice.
275 later on in this page.
277 Installing a new disklabel does not in of itself allow your system to boot
278 a kernel using that label.
279 You must also install boot blocks, which is
280 described later on in this manual page.
281 .Ss Editing an existing disk label
282 To edit an existing disk label, use the form
290 This command reads the label from the in-core kernel copy, or directly from the
293 flag is also specified.
294 The label is written to a file in ASCII and then
295 supplied to an editor for changes.
296 If no editor is specified in an
298 environment variable,
301 When the editor terminates, the label file is used to rewrite the disk label.
302 Existing bootstrap code is unchanged regardless of whether
307 is specified, no data will be written to the device, and instead the
308 disklabel that would have been written will be printed to stdout.
310 useful to see how a partitioning scheme will work out for a specific disk.
311 .Ss Restoring a disk label from a file
312 To restore a disk label from a file, use the form
318 .Ar disk Ar protofile
321 is capable of restoring a disk label that was previously saved in a file
323 The prototype file used to create the label should be in the same format
324 as that produced when reading or editing a label.
325 Comments are delimited by
328 As when writing a new label, any existing bootstrap code will be
331 is specified and will be unaffected otherwise.
332 See the boot options below for a
333 method of restoring the label and writing the bootstrap at the same time.
336 is used, no data will be written to the device, and instead the
337 disklabel that would have been written will be printed to stdout.
339 useful to see how a partitioning scheme will work out for a specific disk.
340 .Ss Enabling and disabling writing to the disk label area
341 By default, it is not possible to write to the disk label area at the beginning
343 The disk driver arranges for
345 and similar system calls
348 on any attempt to do so.
350 to write to this area (for example, to obliterate the label), use the form
356 To disallow writing to the label area after previously allowing it,
362 .Ss Installing bootstraps
363 The final three forms of
365 are used to install bootstrap code, which allows boot from a
368 If you are creating a
369 .Dq dangerously-dedicated
370 slice for compatibility with older PC systems,
371 you generally want to specify the compatibility slice, such as
373 If you are creating a label within an existing DOS slice,
375 the slice name such as
377 Making a slice bootable can be tricky.
378 If you are using a normal DOS
379 slice you typically install (or leave) a standard MBR on the base disk and
382 bootblocks in the slice.
391 .Oo Ar disktype Ns / Ns Cm auto Oc
393 This form installs the bootstrap only.
394 It does not change the disk label.
395 You should never use this command on the compatibility slice unless you
397 .Dq dangerously-dedicated
400 This command is typically run on a
413 .Ar disk Ar disktype Ns / Ns Cm auto
416 This form corresponds to the
418 command described above.
419 In addition to writing a new volume label, it also installs the bootstrap.
420 If run on the compatibility slice this command will create a
421 .Dq dangerously-dedicated
423 This command is normally run on a
425 slice rather than the compatibility slice.
428 is used, no data will be written to the device, and instead the
429 disklabel that would have been written will be printed to stdout.
439 .Ar disk Ar protofile
440 .Oo Ar disktype Ns / Ns Cm auto Oc
442 This form corresponds to the
444 command described above.
445 In addition to restoring the volume label, it also installs the bootstrap.
446 If run on the compatibility slice this command will create a
447 .Dq dangerously-dedicated
449 This command is normally run on a
451 slice rather than the compatibility
454 The bootstrap commands always access the disk directly,
455 so it is not necessary to specify the
460 is used, no data will be written to the device, and instead the
461 disklabel that would have been written will be printed to stdout.
463 The bootstrap code is comprised of two boot programs.
464 Specify the name of the
465 boot programs to be installed in one of these ways:
468 Specify the names explicitly with the
474 indicates the primary boot program and
476 the secondary boot program.
477 The boot programs are normally located in
484 flags are not specified, but
486 was specified, the names of the programs are taken from the
492 entry for the disk if the disktab entry exists and includes those parameters.
494 Otherwise, the default boot image names are used:
498 for the standard stage1 and stage2 boot images.
500 .Ss Initializing/Formatting a bootable disk from scratch
501 To initialize a disk from scratch the following sequence is recommended.
502 Please note that this will wipe everything that was previously on the disk,
512 to initialize the hard disk, and create a GPT or MBR slice table,
514 .Dq "partition table"
522 to define partitions on
524 slices created in the previous step.
530 to create file systems on new partitions.
533 A typical partitioning scheme would be to have an
536 of approximately 512MB to hold the root file system, a
539 swap (usually 4GB), a
551 (usually around 4GB),
556 (usually all remaining space).
557 If you are tight on space all sizes can be halved.
558 Your mileage may vary.
561 .Dl "disklabel32 -w -B da0s1 auto"
562 .Dl "disklabel32 -e da0s1"
565 no longer snoop-adjusts the on-disk label when reading or writing
568 is now responsible for adjusting the label when operating in raw mode.
571 disklabels store offsets as absolute block numbers
572 rather than slice-relative block numbers.
575 is unable to issue the
577 ioctl to get slice information it will
578 refuse to read or write the label in raw mode.
581 option may be used to force the operation by supplying a manual offset.
583 .Bl -tag -width ".Pa /etc/disktab" -compact
585 Default stage1 boot image.
587 Default stage2 boot image.
589 Disk description file.
591 .Sh SAVED FILE FORMAT
596 version of the label when examining, editing, or restoring a disk label.
598 .Bd -literal -offset 4n
607 sectors/cylinder: 1512
609 sectors/unit: 243581184
614 headswitch: 0 # milliseconds
615 track-to-track seek: 0 # milliseconds
620 a: 1048560 16 4.2BSD # 511.992MB
621 b: 8388608 1048576 swap # 4096.000MB
622 c: 243581184 0 unused # 118936.125MB
623 d: 4194304 9437184 4.2BSD # 2048.000MB
624 e: 4194304 13631488 4.2BSD # 2048.000MB
625 f: 8388608 17825792 4.2BSD # 4096.000MB
626 h: 196395264 26214400 HAMMER # 95896.125MB
627 i: 10485760 222609664 ccd # 5120.000MB
628 j: 10485760 233095424 vinum # 5120.000MB
631 Lines starting with a
634 Most of the other specifications are no longer used.
635 The ones which must still be set correctly are:
638 is an optional label, set by the
640 option when writing a label.
647 is set for removable media drives, but no current
649 driver evaluates this
652 is no longer supported;
654 specifies that the drive can perform bad sector remapping.
656 describes the total size of the disk.
657 This value must be correct.
658 .It Ar "the partition table"
661 partition table, not the
663 partition table described in
667 The partition table can have up to 16 entries.
668 It contains the following information:
669 .Bl -tag -width indent
671 The partition identifier is a single letter in the range
675 By convention, partition
677 is reserved to describe the entire disk.
679 The size of the partition in sectors,
683 (megabytes - 1024*1024),
685 (gigabytes - 1024*1024*1024),
687 (gigabytes - 1024*1024*1024*1024),
689 (percentage of free space
691 removing any fixed-size partitions other than partition
695 (all remaining free space
697 fixed-size and percentage partitions).
702 indicates the entire disk.
703 Lowercase versions of
708 Size and type should be specified without any spaces between them.
710 Example: 2097152, 1G, 1024M and 1048576K are all the same size
711 (assuming 512-byte sectors).
713 The offset of the start of the partition from the beginning of the
718 calculate the correct offset to use (the end of the previous partition plus
719 one, ignoring partition
724 will be interpreted as an offset of 0.
726 Describes the purpose of the partition.
727 The example shows all currently used partition types.
730 file systems, use type
734 file systems, use type
740 For Vinum drives, use type
742 Other common types are
746 By convention, partition
748 represents the entire slice and should be of type
752 does not enforce this convention.
756 also knows about a number of other partition types,
757 none of which are in current use.
765 The remainder of the line is a comment and shows the size of
768 .Dl "disklabel32 da0s1"
770 Display the in-core label for the first slice of the
772 disk, as obtained via
775 .Dq dangerously-dedicated ,
776 the compatibility slice name should be specified, such as
779 .Dl "disklabel32 da0s1 > savedlabel"
781 Save the in-core label for
785 This file can be used with the
787 option to restore the label at a later date.
789 .Dl "disklabel32 -w -r /dev/da0s1 da2212 foo"
793 based on information for
797 Any existing bootstrap code will be clobbered
798 and the disk rendered unbootable.
800 .Dl "disklabel32 -e -r da0s1"
802 Read the on-disk label for
804 edit it, and reinstall in-core as well as on-disk.
805 Existing bootstrap code is unaffected.
807 .Dl "disklabel32 -e -r -n da0s1"
809 Read the on-disk label for
811 edit it, and display what the new label would be (in sectors).
814 install the new label either in-core or on-disk.
816 .Dl "disklabel32 -r -w da0s1 auto"
818 Try to auto-detect the required information from
820 and write a new label to the disk.
824 partitioning and file system information.
826 .Dl "disklabel32 -R da0s1 savedlabel"
828 Restore the on-disk and in-core label for
832 Existing bootstrap code is unaffected.
834 .Dl "disklabel32 -R -n da0s1 label_layout"
836 Display what the label would be for
838 using the partition layout in
840 This is useful for determining how much space would be allotted for various
841 partitions with a labelling scheme using
847 .Dl "disklabel32 -B da0s1"
849 Install a new bootstrap on
851 The boot code comes from
855 On-disk and in-core labels are unchanged.
857 .Dl "disklabel32 -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212"
859 Install a new label and bootstrap.
860 The label is derived from disktab information for
862 and installed both in-core and on-disk.
863 The bootstrap code comes from the files
868 .Dl "dd if=/dev/zero of=/dev/da0 bs=512 count=32"
870 .Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32"
871 .Dl "disklabel32 -w -B da0s1 auto"
872 .Dl "disklabel32 -e da0s1"
874 Completely wipe any prior information on the disk, creating a new bootable
875 disk with a DOS partition table containing one
879 initialize the slice, then edit it to your needs.
882 commands are optional, but may be necessary for some BIOSes to properly
885 .Dl "disklabel32 -W da0s1"
886 .Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32"
887 .Dl "disklabel64 -r -w da0s1 auto"
888 .Dl "disklabel64 -N da0s1"
890 Completely wipe any prior information on the slice,
891 changing label format to 64 bit.
892 The wiping is needed as
897 won't do any operations if label with other format is already installed.
899 This is an example disklabel that uses some of the new partition size types
904 which could be used as a source file for
906 .Dl "disklabel32 -R ad0s1 new_label_file"
907 .Bd -literal -offset 4n
916 sectors/cylinder: 1008
918 sectors/unit: 40959009
923 headswitch: 0 # milliseconds
924 track-to-track seek: 0 # milliseconds
937 The kernel device drivers will not allow the size of a disk partition
938 to be decreased or the offset of a partition to be changed while it is open.
939 Some device drivers create a label containing only a single large partition
940 if a disk is unlabeled; thus, the label must be written to the
942 partition of the disk while it is open.
943 This sometimes requires the desired
944 label to be set in two steps, the first one creating at least one other
945 partition, and the second setting the label on the new partition while
950 On some machines the bootstrap code may not fit entirely in the area
951 allocated for it by some file systems.
952 As a result, it may not be possible to have file systems on some partitions
956 When installing bootstrap code,
958 checks for these cases.
959 If the installed boot code would overlap a partition of type
965 utility will disallow creation of file systems on
968 Conversely, if a partition has a type other than
973 will not install bootstrap code that overlaps it.
977 storing sector numbers in 32 bit format
979 is restricted to 2TB, using the prevalent sector size of 512B.
981 labels should be used to partition larger disks.
985 use slightly different versions of
988 and are not generally compatible.
991 kernel can often use labels from other
993 for read-only operation.
1005 .Xr newfs_hammer 8 ,
1008 For the i386 architecture, the primary bootstrap sector contains
1014 utility takes care to not clobber it when installing a bootstrap only
1016 or when editing an existing label
1018 but it unconditionally writes the primary bootstrap program onto
1025 table by the dummy one in the bootstrap program.
1027 concern if the disk is fully dedicated, so that the
1030 starts at absolute block 0 on the disk.
1035 does not perform all possible error checking.
1039 overlap; if an absolute offset does not match the expected offset; if the
1041 partition does not start at 0 or does not cover the entire slice; if a
1042 partition runs past the end of the device; and a number of other errors; but
1043 no warning is given if space remains unused.
tuxillo's projects / dragonfly.git / blob