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31 .\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94
39 .Nd read and write BSD label
43 .Ar disk | Fl f Ar file
47 .Op Fl B Op Fl b Ar boot
49 .Ar disk | Fl f Ar file
54 .Op Fl B Op Fl b Ar boot
56 .Ar disk | Fl f Ar file
60 .Op Fl B Op Fl b Ar boot
63 .Ar disk | Fl f Ar file
69 installs, examines or modifies the
71 label on a disk partition, or on a file containing a partition image.
74 can install bootstrap code.
76 When specifying the device (i.e., when the
81 path prefix may be omitted;
84 utility will automatically prepend it.
88 option enables processing of the historical parts of the
91 If the option is not given, suitable values are set for these fields.
97 that the program will operate on a file instead of a disk partition.
103 program right before the disk would have been modified, and displays
104 the result instead of writing it.
110 to use a layout suitable for a different architecture.
111 Current valid values are
115 If this option is omitted,
117 will use a layout suitable for the current machine.
118 .Ss Reading the Disk Label
119 To examine the label on a disk drive, use the form
127 represents the disk in question, and may be in the form
131 It will display the partition layout.
132 .Ss Writing a Standard Label
133 To write a standard label, use the form
144 is specified, the entry of that name in the
146 file is used; otherwise, or if the type is specified as 'auto', a default
148 .Ss Editing an Existing Disk Label
149 To edit an existing disk label, use the form
157 This command opens the disk label in the default editor, and when the editor
158 exits, the label is validated and if OK written to disk.
159 .Ss Restoring a Disk Label From a File
160 To restore a disk label from a file, use the form
171 is capable of restoring a disk label that was previously saved in a file in
174 The prototype file used to create the label should be in the same format as that
175 produced when reading or editing a label.
176 Comments are delimited by
179 .Ss Installing Bootstraps
182 option is specified, bootstrap code will be read from the file
184 and written to the disk.
187 option allows a different file to be used.
189 .Bl -tag -width ".Pa /etc/disktab" -compact
193 Disk description file.
195 .Sh SAVED FILE FORMAT
201 version of the label when examining, editing, or restoring a disk
204 .Bd -literal -offset 4n
207 # size offset fstype [fsize bsize bps/cpg]
208 a: 81920 16 4.2BSD 2048 16384 5128
209 b: 1091994 81936 swap
210 c: 1173930 0 unused 0 0 # "raw" part, don't edit
215 option is specified, the format is:
216 .Bd -literal -offset 4n
225 sectors/cylinder: 969
227 sectors/unit: 1173930
232 headswitch: 0 # milliseconds
233 track-to-track seek: 0 # milliseconds
237 # size offset fstype [fsize bsize bps/cpg]
238 a: 81920 16 4.2BSD 1024 8192 16
240 c: 1173930 0 unused 0 0 # "raw" part, don't edit
243 Lines starting with a
247 The partition table can have up to 8 entries.
248 It contains the following information:
249 .Bl -tag -width indent
251 The partition identifier is a single letter in the range
255 By convention, partition
257 is reserved to describe the entire disk.
259 The size of the partition in sectors,
263 (megabytes - 1024*1024),
265 (gigabytes - 1024*1024*1024),
267 (percentage of free space
269 removing any fixed-size partitions other than partition
273 (all remaining free space
275 fixed-size and percentage partitions).
280 indicates the entire disk.
281 Lowercase versions of suffixes
286 Size and suffix should be specified without any spaces between them.
288 Example: 2097152, 1G, 1024M and 1048576K are all the same size
289 (assuming 512-byte sectors).
291 The offset of the start of the partition from the beginning of the
296 calculate the correct offset to use (the end of the previous partition plus
297 one, ignoring partition
302 will be interpreted as an offset of 0.
303 The first partition should start at offset 16, because the first 16 sectors are
304 reserved for metadata.
306 Describes the purpose of the partition.
307 The above example shows all currently used partition types.
314 For Vinum drives, use type
316 Other common types are
320 By convention, partition
322 represents the entire slice and should be of type
326 does not enforce this convention.
330 also knows about a number of other partition types,
331 none of which are in current use.
332 (See the definitions starting with
340 file systems only, the fragment size; see
345 file systems only, the block size; see
350 file systems, the number of cylinders in a cylinder group; see
354 Display the label for the first slice of the
356 disk, as obtained via
361 Save the in-core label for
365 This file can be used with the
367 option to restore the label at a later date:
369 .Dl "bsdlabel da0s1 > savedlabel"
374 .Dl "bsdlabel -w /dev/da0s1"
378 edit it, and install the result:
380 .Dl "bsdlabel -e da0s1"
382 Read the on-disk label for
384 edit it, and display what the new label would be (in sectors).
387 install the new label either in-core or on-disk:
389 .Dl "bsdlabel -e -n da0s1"
391 Write a default label on
396 partitioning and file system information:
398 .Dl "bsdlabel -w da0s1"
400 Restore the on-disk and in-core label for
405 .Dl "bsdlabel -R da0s1 savedlabel"
407 Display what the label would be for
409 using the partition layout in
411 This is useful for determining how much space would be allotted for various
412 partitions with a labeling scheme using
418 .Dl "bsdlabel -R -n da0s1 label_layout"
420 Install a new bootstrap on
422 The boot code comes from
425 .Dl "bsdlabel -B da0s1"
427 Install a new label and bootstrap.
428 The bootstrap code comes from the file
430 in the current working directory:
432 .Dl "bsdlabel -w -B -b newboot /dev/da0s1"
434 Completely wipe any prior information on the disk, creating a new bootable
437 partition table containing one slice, covering the whole disk.
438 Initialize the label on this slice,
442 commands are optional, but may be necessary for some
446 .Bd -literal -offset indent
447 dd if=/dev/zero of=/dev/da0 bs=512 count=32
448 gpart create -s MBR da0
449 gpart add -t freebsd da0
450 gpart set -a active -i 1 da0
451 gpart bootcode -b /boot/mbr da0
452 dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
457 This is an example disk label that uses some of the new partition size types
462 which could be used as a source file for
463 .Dq Li "bsdlabel -R ada0s1 new_label_file" :
464 .Bd -literal -offset 4n
468 # size offset fstype [fsize bsize bps/cpg]
469 a: 400M 16 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
477 The kernel device drivers will not allow the size of a disk partition
478 to be decreased or the offset of a partition to be changed while it is open.
482 to store the number of sectors,
484 labels are restricted to a maximum of 2^32-1 sectors.
485 This usually means 2TB of disk space.
486 Larger disks should be partitioned using another method such as
491 all use slightly different versions of
494 are not generally compatible.