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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 $
37 .\" $DragonFly: src/sbin/disklabel64/disklabel64.8,v 1.13 2008/09/16 20:45:36 thomas Exp $
39 .Dd September 28, 2009
44 .Nd read and write 64 bit disk pack label
53 .Ar disk Ar disktype Ns / Ns Cm auto
76 .Oo Ar disktype Ns / Ns Cm auto Oc
85 .Ar disk Ar disktype Ns / Ns Cm auto
96 .Oo Ar disktype Ns / Ns Cm auto Oc
101 installs, examines or modifies a 64 bit label on a disk drive or pack.
103 the label, it can be used to change the drive identification, the disk
104 partitions on the drive, or to replace a damaged label.
105 There are several forms
106 of the command that read (display), install or edit the label on a disk.
110 can install bootstrap code.
111 .Ss Raw or in-core label
112 The disk label resides close to or at the beginning of each disk slice.
113 For faster access, the kernel maintains a copy in core at all times.
115 default, most forms of the
117 command access the in-core copy of the label.
118 To access the raw (on-disk)
122 This option allows a label to be installed on a disk without kernel
123 support for a label, such as when labels are first installed on a system; it
124 must be used when first installing a label on a disk.
125 The specific effect of
127 is described under each command.
131 forms require a disk device name, which should always be the raw
132 device name representing the disk or slice.
134 uses the following scheme for slice numbering:
135 If the disk doesn't use GPT (typically laid out by
137 but e.g.\& MBR (typically laid out by
141 represents the entire disk regardless of any DOS partitioning.
142 Slice 0 is called the compatibility slice,
143 and slice 1 and onward, e.g.\&
148 If the disk does use GPT, then all slices are
150 slices, slice 0 isn't special, it is just the first slice on the disk.
151 You do not have to include the
153 path prefix when specifying the device.
156 utility will automatically prepend it.
157 .Ss Reading the disk label
158 To examine the label on a disk drive, use
167 represents the raw disk in question, and may be in the form
171 It will display all of the parameters associated with the drive and its
176 the kernel's in-core copy of the label is displayed;
177 if the disk has no label, or the partition types on the disk are incorrect,
178 the kernel may have constructed or modified the label.
183 reads the label from the raw disk and displays it.
184 Both versions are usually
185 identical except in the case where a label has not yet been initialized or
187 .Ss Writing a standard label
188 To write a standard label, use the form
194 .Ar disk Ar disktype Ns / Ns Cm auto
197 The required arguments to
199 are the drive to be labeled and the drive type as described in the
202 The drive parameters and partitions are taken from that file.
204 different disks of the same physical type are to have different partitions, it
205 will be necessary to have separate disktab entries describing each, or to edit
206 the label after installation as described below.
207 The optional argument is a
208 pack identification string, up to 16 characters long.
210 quoted if it contains blanks.
214 flag is given, no data will be written to the device, and instead the
215 disklabel that would have been written will be printed to stdout.
219 flag is given, the disk sectors containing the label and bootstrap
220 will be written directly.
221 A side-effect of this is that any existing bootstrap code will be overwritten
222 and the disk rendered unbootable.
223 See the boot options below for a method of
224 writing the label and the bootstrap at the same time.
228 the existing label will be updated via the in-core copy and any bootstrap
229 code will be unaffected.
230 If the disk does not already have a label, the
233 In either case, the kernel's in-core label is replaced.
235 For a virgin disk that is not known to
240 In this case, the driver is requested to produce a virgin label for the
242 This might or might not be successful, depending on whether the
243 driver for the disk is able to get the required data without reading
244 anything from the disk at all.
245 It will likely succeed for all SCSI
246 disks, most IDE disks, and vnode devices.
247 Writing a label to the
248 disk is the only supported operation, and the
250 itself must be provided as the canonical name, i.e.\& not as a full
253 For most harddisks, a label based on percentages for most partitions (and
254 one partition with a size of
256 will produce a reasonable configuration.
258 PC-based systems have special requirements in order for the BIOS to properly
262 Older systems may require what is known as a
263 .Dq dangerously dedicated
264 disklabel, which creates a fake DOS partition to work around problems older
265 BIOSes have with modern disk geometries.
266 On newer systems you generally want
267 to create a normal DOS partition using
271 disklabel within that slice.
273 later on in this page.
275 Installing a new disklabel does not in of itself allow your system to boot
276 a kernel using that label.
277 You must also install boot blocks, which is
278 described later on in this manual page.
279 .Ss Editing an existing disk label
280 To edit an existing disk label, use the form
288 This command reads the label from the in-core kernel copy, or directly from the
291 flag is also specified.
292 The label is written to a file in ASCII and then
293 supplied to an editor for changes.
294 If no editor is specified in an
296 environment variable,
299 When the editor terminates, the label file is used to rewrite the disk label.
300 Existing bootstrap code is unchanged regardless of whether
305 is specified, no data will be written to the device, and instead the
306 disklabel that would have been written will be printed to stdout.
308 useful to see how a partitioning scheme will work out for a specific disk.
309 .Ss Restoring a disk label from a file
310 To restore a disk label from a file, use the form
316 .Ar disk Ar protofile
319 is capable of restoring a disk label that was previously saved in a file
321 The prototype file used to create the label should be in the same format
322 as that produced when reading or editing a label.
323 Comments are delimited by
326 As when writing a new label, any existing bootstrap code will be
329 is specified and will be unaffected otherwise.
330 See the boot options below for a
331 method of restoring the label and writing the bootstrap at the same time.
334 is used, no data will be written to the device, and instead the
335 disklabel that would have been written will be printed to stdout.
337 useful to see how a partitioning scheme will work out for a specific disk.
338 .Ss Enabling and disabling writing to the disk label area
339 By default, it is not possible to write to the disk label area at the beginning
341 The disk driver arranges for
343 and similar system calls
346 on any attempt to do so.
348 to write to this area (for example, to obliterate the label), use the form
354 To disallow writing to the label area after previously allowing it,
360 .Ss Installing bootstraps
361 The final three forms of
363 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.
562 .Dl "disklabel64 -B -r -w da0s0 auto"
563 .Dl "disklabel64 -e da0s0"
565 When a virgin disklabel64 is layed down a
567 or later kernel will align the partition start offset relative to the
568 physical drive instead of relative to the slice start.
569 This overcomes the issue of fdisk creating a badly aligned slice by default.
570 The kernel will use a 1MiB (1024 * 1024 byte) alignment.
571 The purpose of this alignment is to match swap and cluster operations
572 against the physical block size of the underlying device.
574 Even though nearly all devices still report a logical sector size of 512,
575 newer hard drives are starting to use larger physical sector sizes
576 and, in particular, solid state drives (SSDs) use a physical block size
577 of 64K (SLC) or 128K (MLC). We choose a 1 megabyte alignment to cover our
578 bases down the road. 64-bit disklabels are not designed to be put on
579 ultra-tiny storage devices.
581 It is worth noting that aligning cluster operations is particularly
582 important for SSDs and doubly so when
585 Swapcache is able to use large bulk writes which greatly reduces the degree
586 of write magnification on SSD media and it is possible to get upwards of
587 5x more endurance out of the device than the vendor spec sheet indicates.
589 .Bl -tag -width ".Pa /boot/boot2_64" -compact
590 .It Pa /boot/boot1_64
591 Default stage1 boot image.
592 .It Pa /boot/boot2_64
593 Default stage2 boot image.
595 Disk description file.
597 .Sh SAVED FILE FORMAT
602 version of the label when examining, editing, or restoring a disk label.
604 .Bd -literal -offset 4n
607 # Informational fields calculated from the above
608 # All byte equivalent offsets must be aligned
610 # boot space: 32768 bytes
611 # data space: 121790552 blocks # 118936.09 MB (124713525248 bytes)
613 diskid: 5e3ef4db-4e24-11dd-8318-010e0cd0bad1
615 boot2 data base: 0x000000001000
616 partitions data base: 0x000000009000
617 partitions data stop: 0x001d0981f000
618 backup label: 0x001d0981f000
619 total size: 0x001d09820000 # 118936.12 MB
621 display block size: 1024 # for partition display only
624 # size offset fstype fsuuid
625 a: 524288 0 4.2BSD # 512.000MB
626 b: 4194304 524288 swap # 4096.000MB
627 d: 2097152 4718592 4.2BSD # 2048.000MB
628 e: 2097152 6815744 4.2BSD # 2048.000MB
629 f: 4194304 8912896 4.2BSD # 4096.000MB
630 g: 4194304 13107200 4.2BSD # 4096.000MB
631 h: 94003288 17301504 HAMMER # 91800.086MB
632 i: 5242880 111304792 ccd # 5120.000MB
633 j: 5242880 116547672 vinum # 5120.000MB
634 a-stor_uuid: 4370efdb-4e25-11dd-8318-010e0cd0bad1
635 b-stor_uuid: 4370eff4-4e25-11dd-8318-010e0cd0bad1
636 d-stor_uuid: 4370f00b-4e25-11dd-8318-010e0cd0bad1
637 e-stor_uuid: 4370f024-4e25-11dd-8318-010e0cd0bad1
638 f-stor_uuid: 4370f03a-4e25-11dd-8318-010e0cd0bad1
639 g-stor_uuid: 4370f053-4e25-11dd-8318-010e0cd0bad1
640 h-stor_uuid: 4370f06a-4e25-11dd-8318-010e0cd0bad1
641 i-stor_uuid: 4370f083-4e25-11dd-8318-010e0cd0bad1
642 j-stor_uuid: 4370f099-4e25-11dd-8318-010e0cd0bad1
645 Lines starting with a
648 The specifications which can be changed are:
651 is an optional label, set by the
653 option when writing a label.
654 .It Ar "the partition table"
657 partition table, not the
659 partition table described in
663 The partition table can have up to 16 entries.
664 It contains the following information:
665 .Bl -tag -width indent
667 The partition identifier is a single letter in the range
672 The size of the partition in sectors,
676 (megabytes - 1024*1024),
678 (gigabytes - 1024*1024*1024),
680 (percentage of free space
682 removing any fixed-size partitions),
684 (all remaining free space
686 fixed-size and percentage partitions).
687 Lowercase versions of
692 Size and type should be specified without any spaces between them.
694 Example: 2097152, 1G, 1024M and 1048576K are all the same size
695 (assuming 512-byte sectors).
697 The offset of the start of the partition from the beginning of the
702 calculate the correct offset to use (the end of the previous partition plus
705 Describes the purpose of the partition.
706 The example shows all currently used partition types.
709 file systems, use type
713 file systems, use type
719 For Vinum drives, use type
721 Other common types are
728 also knows about a number of other partition types,
729 none of which are in current use.
737 The remainder of the line is a comment and shows the size of
740 .Dl "disklabel64 da0s1"
742 Display the in-core label for the first slice of the
744 disk, as obtained via
747 .Dq dangerously-dedicated ,
748 the compatibility slice name should be specified, such as
751 .Dl "disklabel64 da0s1 > savedlabel"
753 Save the in-core label for
757 This file can be used with the
759 option to restore the label at a later date.
761 .Dl "disklabel64 -w -r /dev/da0s1 da2212 foo"
765 based on information for
769 Any existing bootstrap code will be clobbered
770 and the disk rendered unbootable.
772 .Dl "disklabel64 -e -r da0s1"
774 Read the on-disk label for
776 edit it, and reinstall in-core as well as on-disk.
777 Existing bootstrap code is unaffected.
779 .Dl "disklabel64 -e -r -n da0s1"
781 Read the on-disk label for
783 edit it, and display what the new label would be (in sectors).
786 install the new label either in-core or on-disk.
788 .Dl "disklabel64 -r -w da0s1 auto"
790 Try to auto-detect the required information from
792 and write a new label to the disk.
795 command to edit the partitioning information.
797 .Dl "disklabel64 -R da0s1 savedlabel"
799 Restore the on-disk and in-core label for
803 Existing bootstrap code is unaffected.
805 .Dl "disklabel64 -R -n da0s1 label_layout"
807 Display what the label would be for
809 using the partition layout in
811 This is useful for determining how much space would be allotted for various
812 partitions with a labelling scheme using
818 .Dl "disklabel64 -B da0s1"
820 Install a new bootstrap on
822 The boot code comes from
826 On-disk and in-core labels are unchanged.
828 .Dl "disklabel64 -w -B /dev/da0s1 -b newboot1 -s newboot2 da2212"
830 Install a new label and bootstrap.
831 The label is derived from disktab information for
833 and installed both in-core and on-disk.
834 The bootstrap code comes from the files
839 .Dl "dd if=/dev/zero of=/dev/da0 bs=512 count=32"
841 .Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32"
842 .Dl "disklabel64 -w -B da0s1 auto"
843 .Dl "disklabel64 -e da0s1"
845 Completely wipe any prior information on the disk, creating a new bootable
846 disk with a DOS partition table containing one
850 initialize the slice, then edit it to your needs.
853 commands are optional, but may be necessary for some BIOSes to properly
856 .Dl "disklabel64 -W da0s1"
857 .Dl "dd if=/dev/zero of=/dev/da0s1 bs=512 count=32"
858 .Dl "disklabel -r -w da0s1 auto"
859 .Dl "disklabel -N da0s1"
861 Completely wipe any prior information on the slice,
862 changing label format to 32 bit.
863 The wiping is needed as
868 won't do any operations if label with other format is already installed.
870 This is an example disklabel that uses some of the new partition size types
875 which could be used as a source file for
877 .Dl "disklabel64 -R ad0s1 new_label_file"
878 .Bd -literal -offset 4n
881 # Informational fields calculated from the above
882 # All byte equivalent offsets must be aligned
884 # boot space: 32768 bytes
885 # data space: 121790552 blocks # 118936.09 MB (124713525248 bytes)
887 diskid: b1db58a3-4e26-11dd-8318-010e0cd0bad1
889 boot2 data base: 0x000000001000
890 partitions data base: 0x000000009000
891 partitions data stop: 0x001d0981f000
892 backup label: 0x001d0981f000
893 total size: 0x001d09820000 # 118936.12 MB
895 display block size: 1024 # for partition display only
898 # size offset fstype fsuuid
910 The kernel device drivers will not allow the size of a disk partition
911 to be decreased or the offset of a partition to be changed while it is open.
912 Some device drivers create a label containing only a single large partition
913 if a disk is unlabeled; thus, the label must be written to the
915 partition of the disk while it is open.
916 This sometimes requires the desired
917 label to be set in two steps, the first one creating at least one other
918 partition, and the second setting the label on the new partition while
937 For the i386 architecture, the primary bootstrap sector contains
943 utility takes care to not clobber it when installing a bootstrap only
945 or when editing an existing label
947 but it unconditionally writes the primary bootstrap program onto
954 table by the dummy one in the bootstrap program.
956 concern if the disk is fully dedicated, so that the
959 starts at absolute block 0 on the disk.
964 does not perform all possible error checking.
968 overlap; if an absolute offset does not match the expected offset; if a
969 partition runs past the end of the device; and a number of other errors; but
970 no warning is given if space remains unused.
projects / dragonfly.git / blob