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31 .\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94
34 .Dd September 17, 2005
39 .Nd read and write disk pack 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
112 .Cm i386 , amd64 , ia64 , pc98 ,
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
129 represents the disk in question, and may be in the form
133 It will display the partition layout.
134 .Ss Writing a Standard Label
135 To write a standard label, use the form
144 If the drive type is specified, the entry of that name in the
146 file is used; otherwise a default layout is used.
147 .Ss Editing an Existing Disk Label
148 To edit an existing disk label, use the form
156 This command opens the disk label in the default editor, and when the editor
157 exits, the label is validated and if OK written to disk.
158 .Ss Restoring a Disk Label From a File
159 To restore a disk label from a file, use the form
168 is capable of restoring a disk label that was previously saved in a file in
171 The prototype file used to create the label should be in the same format as that
172 produced when reading or editing a label.
173 Comments are delimited by
176 .Ss Installing Bootstraps
179 argument is specified, bootstrap code will be read from the file
181 and written to the disk.
184 argument allows a different file to be used.
186 .Bl -tag -width ".Pa /etc/disktab" -compact
190 Disk description file.
192 .Sh SAVED FILE FORMAT
198 version of the label when examining, editing, or restoring a disk
201 .Bd -literal -offset 4n
204 # size offset fstype [fsize bsize bps/cpg]
205 a: 81920 16 4.2BSD 1024 8192 16
207 c: 1173930 0 unused 0 0 # "raw" part, don't edit
212 option is specified, the format is:
213 .Bd -literal -offset 4n
222 sectors/cylinder: 969
224 sectors/unit: 1173930
229 headswitch: 0 # milliseconds
230 track-to-track seek: 0 # milliseconds
234 # size offset fstype [fsize bsize bps/cpg]
235 a: 81920 16 4.2BSD 1024 8192 16
237 c: 1173930 0 unused 0 0 # "raw" part, don't edit
240 Lines starting with a
244 The partition table can have up to 8 entries.
245 It contains the following information:
246 .Bl -tag -width indent
248 The partition identifier is a single letter in the range
252 By convention, partition
254 is reserved to describe the entire disk.
256 The size of the partition in sectors,
260 (megabytes - 1024*1024),
262 (gigabytes - 1024*1024*1024),
264 (percentage of free space
266 removing any fixed-size partitions other than partition
270 (all remaining free space
272 fixed-size and percentage partitions).
277 indicates the entire disk.
278 Lowercase versions of
283 Size and type should be specified without any spaces between them.
285 Example: 2097152, 1G, 1024M and 1048576K are all the same size
286 (assuming 512-byte sectors).
288 The offset of the start of the partition from the beginning of the
293 calculate the correct offset to use (the end of the previous partition plus
294 one, ignoring partition
299 will be interpreted as an offset of 0.
300 The first partition should start at offset 16, because the first 16 sectors are
301 reserved for metadata.
303 Describes the purpose of the partition.
304 The example shows all currently used partition types.
311 For Vinum drives, use type
313 Other common types are
317 By convention, partition
319 represents the entire slice and should be of type
323 does not enforce this convention.
327 also knows about a number of other partition types,
328 none of which are in current use.
329 (See the definitions starting with
339 file systems only, the fragment size.
340 Defaults to 1024 for partitions smaller than 1GB,
341 4096 for partitions 1GB or larger.
347 file systems only, the block size.
348 Defaults to 8192 for partitions smaller than 1GB,
349 16384 for partitions 1GB or larger.
353 file systems, the number of cylinders in a cylinder group.
356 file systems, the segment shift value.
357 Defaults to 16 for partitions smaller than 1GB,
358 64 for partitions 1GB or larger.
363 Display the label for the first slice of the
365 disk, as obtained via
368 .Dl "bsdlabel da0s1 > savedlabel"
370 Save the in-core label for
374 This file can be used with the
376 option to restore the label at a later date.
378 .Dl "bsdlabel -w /dev/da0s1"
383 .Dl "bsdlabel -e da0s1"
387 edit it, and install the result.
389 .Dl "bsdlabel -e -n da0s1"
391 Read the on-disk label for
393 edit it, and display what the new label would be (in sectors).
396 install the new label either in-core or on-disk.
398 .Dl "bsdlabel -w da0s1"
400 Write a default label on
405 partitioning and file system information.
407 .Dl "bsdlabel -R da0s1 savedlabel"
409 Restore the on-disk and in-core label for
414 .Dl "bsdlabel -R -n da0s1 label_layout"
416 Display what the label would be for
418 using the partition layout in
420 This is useful for determining how much space would be allotted for various
421 partitions with a labeling scheme using
427 .Dl "bsdlabel -B da0s1"
429 Install a new bootstrap on
431 The boot code comes from
434 .Dl "bsdlabel -w -B -b newboot /dev/da0s1"
436 Install a new label and bootstrap.
437 The bootstrap code comes from the file
439 in the current working directory.
440 .Bd -literal -offset indent
441 dd if=/dev/zero of=/dev/da0 bs=512 count=32
443 dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
448 Completely wipe any prior information on the disk, creating a new bootable
451 partition table containing one slice, covering the whole disk.
452 Initialize the label on this slice,
456 commands are optional, but may be necessary for some
461 This is an example disk label that uses some of the new partition size types
466 which could be used as a source file for
467 .Dq Li "bsdlabel -R ad0s1c new_label_file" :
468 .Bd -literal -offset 4n
472 # size offset fstype [fsize bsize bps/cpg]
473 a: 400M 16 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
481 The kernel device drivers will not allow the size of a disk partition
482 to be decreased or the offset of a partition to be changed while it is open.
486 to store the number of sectors,
488 labels are restricted to a maximum of 2^32-1 sectors.
489 This usually means 2TB of disk space.
490 Larger disks should be partitioned using another method such as
495 all use slightly different versions of
498 are not generally compatible.