xref: /freebsd/sbin/bsdlabel/bsdlabel.8 (revision d6b92ffa) 
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31.\"	@(#)disklabel.8	8.2 (Berkeley) 4/19/94
32.\" $FreeBSD$
33.\"
34.Dd October 5, 2016
35.Dt BSDLABEL 8
36.Os
37.Sh NAME
38.Nm bsdlabel
39.Nd read and write BSD label
40.Sh SYNOPSIS
41.Nm
42.Op Fl A
43.Ar disk | Fl f Ar file
44.Nm
45.Fl w
46.Op Fl \&An
47.Op Fl B Op Fl b Ar boot
48.Op Fl m Ar machine
49.Ar disk | Fl f Ar file
50.Op Ar type
51.Nm
52.Fl e
53.Op Fl \&An
54.Op Fl B Op Fl b Ar boot
55.Op Fl m Ar machine
56.Ar disk | Fl f Ar file
57.Nm
58.Fl R
59.Op Fl \&An
60.Op Fl B Op Fl b Ar boot
61.Op Fl m Ar machine
62.Op Fl f
63.Ar disk | Fl f Ar file
64.Ar protofile
65.Sh DESCRIPTION
66The
67.Nm
68utility
69installs, examines or modifies the
70.Bx
71label on a disk partition, or on a file containing a partition image.
72In addition,
73.Nm
74can install bootstrap code.
75.Ss Disk Device Name
76When specifying the device (i.e., when the
77.Fl f
78option is not used),
79the
80.Pa /dev/
81path prefix may be omitted;
82the
83.Nm
84utility will automatically prepend it.
85.Ss General Options
86The
87.Fl A
88option enables processing of the historical parts of the
89.Bx
90label.
91If the option is not given, suitable values are set for these fields.
92.Pp
93The
94.Fl f
95option tells
96.Nm
97that the program will operate on a file instead of a disk partition.
98.Pp
99The
100.Fl n
101option stops the
102.Nm
103program right before the disk would have been modified, and displays
104the result instead of writing it.
105.Pp
106The
107.Fl m Ar machine
108argument forces
109.Nm
110to use a layout suitable for a different architecture.
111Current valid values are
112.Cm i386
113and
114.Cm amd64 .
115If this option is omitted,
116.Nm
117will use a layout suitable for the current machine.
118.Ss Reading the Disk Label
119To examine the label on a disk drive, use the form
120.Pp
121.Nm
122.Op Fl A
123.Op Fl m Ar machine
124.Ar disk
125.Pp
126.Ar disk
127represents the disk in question, and may be in the form
128.Pa da0
129or
130.Pa /dev/da0 .
131It will display the partition layout.
132.Ss Writing a Standard Label
133To write a standard label, use the form
134.Pp
135.Nm
136.Fl w
137.Op Fl \&An
138.Op Fl m Ar machine
139.Ar disk
140.Op Ar type
141.Pp
142If the drive
143.Ar type
144is specified, the entry of that name in the
145.Xr disktab 5
146file is used; otherwise, or if the type is specified as 'auto', a default
147layout is used.
148.Ss Editing an Existing Disk Label
149To edit an existing disk label, use the form
150.Pp
151.Nm
152.Fl e
153.Op Fl \&An
154.Op Fl m Ar machine
155.Ar disk
156.Pp
157This command opens the disk label in the default editor, and when the editor
158exits, the label is validated and if OK written to disk.
159.Ss Restoring a Disk Label From a File
160To restore a disk label from a file, use the form
161.Pp
162.Nm
163.Fl R
164.Op Fl \&An
165.Op Fl m Ar machine
166.Ar disk protofile
167.Pp
168The
169.Nm
170utility
171is capable of restoring a disk label that was previously saved in a file in
172.Tn ASCII
173format.
174The prototype file used to create the label should be in the same format as that
175produced when reading or editing a label.
176Comments are delimited by
177.Ql #
178and newline.
179.Ss Installing Bootstraps
180If the
181.Fl B
182option is specified, bootstrap code will be read from the file
183.Pa /boot/boot
184and written to the disk.
185The
186.Fl b Ar boot
187option allows a different file to be used.
188.Sh FILES
189.Bl -tag -width ".Pa /etc/disktab" -compact
190.It Pa /boot/boot
191Default boot image.
192.It Pa /etc/disktab
193Disk description file.
194.El
195.Sh SAVED FILE FORMAT
196The
197.Nm
198utility
199uses an
200.Tn ASCII
201version of the label when examining, editing, or restoring a disk
202label.
203The format is:
204.Bd -literal -offset 4n
205
2068 partitions:
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
211.Ed
212.Pp
213If the
214.Fl A
215option is specified, the format is:
216.Bd -literal -offset 4n
217# /dev/da1c:
218type: SCSI
219disk: da0s1
220label:
221flags:
222bytes/sector: 512
223sectors/track: 51
224tracks/cylinder: 19
225sectors/cylinder: 969
226cylinders: 1211
227sectors/unit: 1173930
228rpm: 3600
229interleave: 1
230trackskew: 0
231cylinderskew: 0
232headswitch: 0           # milliseconds
233track-to-track seek: 0  # milliseconds
234drivedata: 0
235
2368 partitions:
237#        size   offset    fstype   [fsize bsize bps/cpg]
238  a:    81920       16    4.2BSD     1024  8192    16
239  b:   160000    81936      swap
240  c:  1173930        0    unused        0     0         # "raw" part, don't edit
241.Ed
242.Pp
243Lines starting with a
244.Ql #
245mark are comments.
246.Pp
247The partition table can have up to 8 entries.
248It contains the following information:
249.Bl -tag -width indent
250.It Ar #
251The partition identifier is a single letter in the range
252.Ql a
253to
254.Ql h .
255By convention, partition
256.Ql c
257is reserved to describe the entire disk.
258.It Ar size
259The size of the partition in sectors,
260.Cm K
261(kilobytes - 1024),
262.Cm M
263(megabytes - 1024*1024),
264.Cm G
265(gigabytes - 1024*1024*1024),
266.Cm %
267(percentage of free space
268.Em after
269removing any fixed-size partitions other than partition
270.Ql c ) ,
271or
272.Cm *
273(all remaining free space
274.Em after
275fixed-size and percentage partitions).
276For partition
277.Ql c ,
278a size of
279.Cm *
280indicates the entire disk.
281Lowercase versions of suffixes
282.Cm K , M ,
283and
284.Cm G
285are allowed.
286Size and suffix should be specified without any spaces between them.
287.Pp
288Example: 2097152, 1G, 1024M and 1048576K are all the same size
289(assuming 512-byte sectors).
290.It Ar offset
291The offset of the start of the partition from the beginning of the
292drive in sectors, or
293.Cm *
294to have
295.Nm
296calculate the correct offset to use (the end of the previous partition plus
297one, ignoring partition
298.Ql c ) .
299For partition
300.Ql c ,
301.Cm *
302will be interpreted as an offset of 0.
303The first partition should start at offset 16, because the first 16 sectors are
304reserved for metadata.
305.It Ar fstype
306Describes the purpose of the partition.
307The above example shows all currently used partition types.
308For
309.Tn UFS
310file systems and
311.Xr ccd 4
312partitions, use type
313.Cm 4.2BSD .
314For Vinum drives, use type
315.Cm vinum .
316Other common types are
317.Cm swap
318and
319.Cm unused .
320By convention, partition
321.Ql c
322represents the entire slice and should be of type
323.Cm unused ,
324though
325.Nm
326does not enforce this convention.
327The
328.Nm
329utility
330also knows about a number of other partition types,
331none of which are in current use.
332(See the definitions starting with
333.Dv FS_UNUSED
334in
335.In sys/disklabel.h
336for more details.)
337.It Ar fsize
338For
339.Cm 4.2BSD
340file systems only, the fragment size; see
341.Xr newfs 8 .
342.It Ar bsize
343For
344.Cm 4.2BSD
345file systems only, the block size; see
346.Xr newfs 8 .
347.It Ar bps/cpg
348For
349.Cm 4.2BSD
350file systems, the number of cylinders in a cylinder group; see
351.Xr newfs 8 .
352.El
353.Sh EXAMPLES
354Display the label for the first slice of the
355.Pa da0
356disk, as obtained via
357.Pa /dev/da0s1 :
358.Pp
359.Dl "bsdlabel da0s1"
360.Pp
361Save the in-core label for
362.Pa da0s1
363into the file
364.Pa savedlabel .
365This file can be used with the
366.Fl R
367option to restore the label at a later date:
368.Pp
369.Dl "bsdlabel da0s1 > savedlabel"
370.Pp
371Create a label for
372.Pa da0s1 :
373.Pp
374.Dl "bsdlabel -w /dev/da0s1"
375.Pp
376Read the label for
377.Pa da0s1 ,
378edit it, and install the result:
379.Pp
380.Dl "bsdlabel -e da0s1"
381.Pp
382Read the on-disk label for
383.Pa da0s1 ,
384edit it, and display what the new label would be (in sectors).
385It does
386.Em not
387install the new label either in-core or on-disk:
388.Pp
389.Dl "bsdlabel -e -n da0s1"
390.Pp
391Write a default label on
392.Pa da0s1 .
393Use another
394.Nm Fl e
395command to edit the
396partitioning and file system information:
397.Pp
398.Dl "bsdlabel -w da0s1"
399.Pp
400Restore the on-disk and in-core label for
401.Pa da0s1
402from information in
403.Pa savedlabel :
404.Pp
405.Dl "bsdlabel -R da0s1 savedlabel"
406.Pp
407Display what the label would be for
408.Pa da0s1
409using the partition layout in
410.Pa label_layout .
411This is useful for determining how much space would be allotted for various
412partitions with a labeling scheme using
413.Cm % Ns -based
414or
415.Cm *
416partition sizes:
417.Pp
418.Dl "bsdlabel -R -n da0s1 label_layout"
419.Pp
420Install a new bootstrap on
421.Pa da0s1 .
422The boot code comes from
423.Pa /boot/boot :
424.Pp
425.Dl "bsdlabel -B da0s1"
426.Pp
427Install a new label and bootstrap.
428The bootstrap code comes from the file
429.Pa newboot
430in the current working directory:
431.Pp
432.Dl "bsdlabel -w -B -b newboot /dev/da0s1"
433.Pp
434Completely wipe any prior information on the disk, creating a new bootable
435disk with a
436.Tn DOS
437partition table containing one slice, covering the whole disk.
438Initialize the label on this slice,
439then edit it.
440The
441.Xr dd 1
442commands are optional, but may be necessary for some
443.Tn BIOS Ns es
444to properly
445recognize the disk:
446.Bd -literal -offset indent
447dd if=/dev/zero of=/dev/da0 bs=512 count=32
448gpart create -s MBR da0
449gpart add -t freebsd da0
450gpart set -a active -i 1 da0
451gpart bootcode -b /boot/mbr da0
452dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
453bsdlabel -w -B da0s1
454bsdlabel -e da0s1
455.Ed
456.Pp
457This is an example disk label that uses some of the new partition size types
458such as
459.Cm % , M , G ,
460and
461.Cm * ,
462which could be used as a source file for
463.Dq Li "bsdlabel -R ada0s1 new_label_file" :
464.Bd -literal -offset 4n
465# /dev/ada0s1:
466
4678 partitions:
468#        size   offset    fstype   [fsize bsize bps/cpg]
469  a:   400M       16    4.2BSD     4096 16384    75    # (Cyl.    0 - 812*)
470  b:     1G        *      swap
471  c:      *        *    unused
472  e: 204800        *    4.2BSD
473  f:     5g        *    4.2BSD
474  g:      *        *    4.2BSD
475.Ed
476.Sh DIAGNOSTICS
477The kernel device drivers will not allow the size of a disk partition
478to be decreased or the offset of a partition to be changed while it is open.
479.Sh COMPATIBILITY
480Due to the use of an
481.Vt uint32_t
482to store the number of sectors,
483.Bx
484labels are restricted to a maximum of 2^32-1 sectors.
485This usually means 2TB of disk space.
486Larger disks should be partitioned using another method such as
487.Xr gpart 8 .
488.Pp
489The various
490.Bx Ns s
491all use slightly different versions of
492.Bx
493labels and
494are not generally compatible.
495.Sh SEE ALSO
496.Xr ccd 4 ,
497.Xr geom 4 ,
498.Xr md 4 ,
499.Xr disktab 5 ,
500.Xr boot0cfg 8 ,
501.Xr gpart 8 ,
502.Xr newfs 8
503.Sh HISTORY
504The
505.Nm disklabel
506utility appeared in
507.Bx 4.3 Tahoe .
508