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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
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 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 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
170 is capable of restoring a disk label that was previously saved in a file in
173 The prototype file used to create the label should be in the same format as that
174 produced when reading or editing a label.
175 Comments are delimited by
178 .Ss Installing Bootstraps
181 option is specified, bootstrap code will be read from the file
183 and written to the disk.
186 option allows a different file to be used.
188 .Bl -tag -width ".Pa /etc/disktab" -compact
192 Disk description file.
194 .Sh SAVED FILE FORMAT
200 version of the label when examining, editing, or restoring a disk
203 .Bd -literal -offset 4n
206 # size offset fstype [fsize bsize bps/cpg]
207 a: 81920 16 4.2BSD 2048 16384 5128
208 b: 1091994 81936 swap
209 c: 1173930 0 unused 0 0 # "raw" part, don't edit
214 option is specified, the format is:
215 .Bd -literal -offset 4n
224 sectors/cylinder: 969
226 sectors/unit: 1173930
231 headswitch: 0 # milliseconds
232 track-to-track seek: 0 # milliseconds
236 # size offset fstype [fsize bsize bps/cpg]
237 a: 81920 16 4.2BSD 1024 8192 16
239 c: 1173930 0 unused 0 0 # "raw" part, don't edit
242 Lines starting with a
246 The partition table can have up to 8 entries.
247 It contains the following information:
248 .Bl -tag -width indent
250 The partition identifier is a single letter in the range
254 By convention, partition
256 is reserved to describe the entire disk.
258 The size of the partition in sectors,
262 (megabytes - 1024*1024),
264 (gigabytes - 1024*1024*1024),
266 (percentage of free space
268 removing any fixed-size partitions other than partition
272 (all remaining free space
274 fixed-size and percentage partitions).
279 indicates the entire disk.
280 Lowercase versions of suffixes
285 Size and suffix should be specified without any spaces between them.
287 Example: 2097152, 1G, 1024M and 1048576K are all the same size
288 (assuming 512-byte sectors).
290 The offset of the start of the partition from the beginning of the
295 calculate the correct offset to use (the end of the previous partition plus
296 one, ignoring partition
301 will be interpreted as an offset of 0.
302 The first partition should start at offset 16, because the first 16 sectors are
303 reserved for metadata.
305 Describes the purpose of the partition.
306 The above example shows all currently used partition types.
313 For Vinum drives, use type
315 Other common types are
319 By convention, partition
321 represents the entire slice and should be of type
325 does not enforce this convention.
329 also knows about a number of other partition types,
330 none of which are in current use.
331 (See the definitions starting with
339 file systems only, the fragment size; see
344 file systems only, the block size; see
349 file systems, the number of cylinders in a cylinder group; see
353 Display the label for the first slice of the
355 disk, as obtained via
360 Save the in-core label for
364 This file can be used with the
366 option to restore the label at a later date:
368 .Dl "bsdlabel da0s1 > savedlabel"
373 .Dl "bsdlabel -w /dev/da0s1"
377 edit it, and install the result:
379 .Dl "bsdlabel -e da0s1"
381 Read the on-disk label for
383 edit it, and display what the new label would be (in sectors).
386 install the new label either in-core or on-disk:
388 .Dl "bsdlabel -e -n da0s1"
390 Write a default label on
395 partitioning and file system information:
397 .Dl "bsdlabel -w da0s1"
399 Restore the on-disk and in-core label for
404 .Dl "bsdlabel -R da0s1 savedlabel"
406 Display what the label would be for
408 using the partition layout in
410 This is useful for determining how much space would be allotted for various
411 partitions with a labeling scheme using
417 .Dl "bsdlabel -R -n da0s1 label_layout"
419 Install a new bootstrap on
421 The boot code comes from
424 .Dl "bsdlabel -B da0s1"
426 Install a new label and bootstrap.
427 The bootstrap code comes from the file
429 in the current working directory:
431 .Dl "bsdlabel -w -B -b newboot /dev/da0s1"
433 Completely wipe any prior information on the disk, creating a new bootable
436 partition table containing one slice, covering the whole disk.
437 Initialize the label on this slice,
441 commands are optional, but may be necessary for some
445 .Bd -literal -offset indent
446 dd if=/dev/zero of=/dev/da0 bs=512 count=32
448 dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
453 This is an example disk label that uses some of the new partition size types
458 which could be used as a source file for
459 .Dq Li "bsdlabel -R ad0s1 new_label_file" :
460 .Bd -literal -offset 4n
464 # size offset fstype [fsize bsize bps/cpg]
465 a: 400M 16 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
473 The kernel device drivers will not allow the size of a disk partition
474 to be decreased or the offset of a partition to be changed while it is open.
478 to store the number of sectors,
480 labels are restricted to a maximum of 2^32-1 sectors.
481 This usually means 2TB of disk space.
482 Larger disks should be partitioned using another method such as
487 all use slightly different versions of
490 are not generally compatible.