1 .\" $FreeBSD: src/sbin/i386/fdisk/fdisk.8,v 1.17.2.11 2002/04/25 16:25:12 trhodes Exp $
8 .Nd PC slice table maintenance program
21 In order for the BIOS to boot the kernel,
22 certain conventions must be adhered to.
23 Sector 0 of the disk must contain boot code,
26 BIOS slices can be used to break the disk up into several pieces.
27 The BIOS brings in sector 0 and verifies the magic number. The sector
28 0 boot code then searches the slice table to determine which
31 This boot code then brings in the bootstrap from the
33 slice and, if marked bootable, runs it.
35 you can have one or more slices with one
39 program can be used to divide space on the disk into slices and set one
46 serves a similar purpose to the DOS program. The first form is used to
47 display slice information or to interactively edit the slice
48 table. The second is used to write a slice table using a
50 and is designed to be used by other scripts/programs.
54 Change the active slice only. Ignored if
58 Get the boot code from the file
63 Reinitialize the boot code contained in sector 0 of the disk. Ignored
67 .It Fl f Ar configfile
68 Set slice values using the file
72 always modifies existing slices, unless
74 is also given, in which case all existing slices are deleted (marked
75 as "unused") before the
79 can be "-", in which case
82 .Sx CONFIGURATION FILE ,
83 below, for file syntax.
88 is used, you are not asked if you really want to write the slices
89 table (as you are in the interactive mode). Use with caution!
91 Initialize sector 0 of the disk. This implies
97 Initialize the contents of sector 0
100 slice covering the entire disk.
102 Print summary information and exit.
104 Test mode; do not write slice values. Generally used with the
106 option to see what would be written to the slice table. Implies
109 Is used for updating (editing) sector 0 of the disk. Ignored if
117 prints out the slice table that is written to the disk.
119 Operate on a single fdisk entry only. Ignored if
124 The final disk name can be provided as a
126 disk name only, e.g.\&
128 or as a fully qualified device node under
130 If omitted, the disks
134 are searched in that order, until one is found to respond.
136 When called without options,
138 prints the sector 0 slice table.
141 ******* Working on device /dev/ad0 *******
142 parameters extracted from in-core disklabel are:
143 cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
145 parameters to be used for BIOS calculations are:
146 cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
148 Warning: BIOS sector numbering starts with sector 1
149 Information from DOS bootblock is:
150 The data for partition 1 is:
151 sysid 165,(FreeBSD/NetBSD/386BSD)
152 start 495, size 380160 (185 Meg), flag 0
153 beg: cyl 1/ sector 1/ head 0;
154 end: cyl 768/ sector 33/ head 14
155 The data for partition 2 is:
157 start 378180, size 2475 (1 Meg), flag 0
158 beg: cyl 764/ sector 1/ head 0;
159 end: cyl 768/ sector 33/ head 14
160 The data for partition 3 is:
162 The data for partition 4 is:
163 sysid 99,(ISC UNIX, other System V/386, GNU HURD or Mach)
164 start 380656, size 224234 (109 Meg), flag 80
165 beg: cyl 769/ sector 2/ head 0;
166 end: cyl 197/ sector 33/ head 14
169 The disk is divided into three slices that happen to fill the disk.
170 The second slice overlaps the end of the first.
171 (Used for debugging purposes.)
172 .Bl -tag -width "cyl, sector and head"
174 is used to label the slice.
177 magic number 165 decimal (A5 in hex).
178 .It Em start No and Em size
179 fields provide the start address
180 and size of a slice in sectors.
182 specifies that this is the active slice.
183 .It Em cyl , sector No and Em head
184 fields are used to specify the beginning and end addresses of the slice.
186 these numbers are calculated using BIOS's understanding of the disk geometry
187 and saved in the bootblock.
194 flags are used to indicate that the slice data is to be updated.
197 option is also given,
199 will enter a conversational mode.
200 In this mode, no changes will be written to disk unless you explicitly tell
205 will display each slice and ask whether you want to edit it.
208 will step through each field, show you the old value,
209 and ask you for a new one.
210 When you are done with the slice,
212 will display it and ask you whether it is correct.
214 will then proceed to the next entry.
220 fields correct is tricky, so by default,
221 they will be calculated for you;
222 you can specify them if you choose to though.
224 After all the slices are processed,
225 you are given the option to change the
228 Finally, when all the new data for sector 0 has been accumulated,
229 you are asked to confirm whether you really want to rewrite it.
231 The difference between the
238 flag just edits (updates) the fields as they appear on the disk,
241 flag is used to "initialize" sector 0;
242 it will set up the last BIOS slice to use the whole disk for
246 The automatic calculation of starting cylinder etc. uses
247 a set of figures that represent what the BIOS thinks the
248 geometry of the drive is.
249 These figures are taken from the in-core disklabel by default,
252 initially gives you an opportunity to change them.
253 This allows you to create a bootblock that can work with drives
254 that use geometry translation under the BIOS.
256 If you hand craft your disk layout,
257 please make sure that the
259 slice starts on a cylinder boundary.
260 A number of decisions made later may assume this.
261 (This might not be necessary later.)
263 Editing an existing slice will most likely result in the loss of
264 all data in that slice.
268 interactively once or twice to see how it works.
269 This is completely safe as long as you answer the last question
270 in the negative. There are subtleties that
272 detects that are not fully explained in this manual page.
273 .Sh CONFIGURATION FILE
276 option is given, a disk's slice table can be written using values
279 The syntax of this file is very simple;
280 each line is either a comment or a specification, as follows:
286 Lines beginning with a "#" are comments and are ignored.
293 Set the BIOS geometry used in slice calculations. There must be
294 three values specified, with a letter preceding each number:
299 Set the number of cylinders to
304 Set the number of heads to
309 Set the number of sectors/track to
313 These specs can occur in any order, as the leading letter determines
314 which value is which; however, all three must be specified.
316 This line must occur before any lines that specify slice
319 It is an error if the following is not true:
320 .Bd -literal -offset indent
321 1 <= number of cylinders
322 1 <= number of heads <= 256
323 1 <= number of sectors/track < 64
326 The number of cylinders should be less than or equal to 1024, but this
327 is not enforced, although a warning will be printed. Note that bootable
329 slices (the "/" filesystem) must lie completely within the
330 first 1024 cylinders; if this is not true, booting may fail.
331 Non-bootable slices do not have this restriction.
333 Example (all of these are equivalent), for a disk with 1019 cylinders,
334 39 heads, and 63 sectors:
335 .Bd -literal -offset indent
347 Set the slice given by
357 Only those slices explicitly mentioned by these lines are modified;
358 any slice not referenced by a "p" line will not be modified.
359 However, if an invalid slice table is present, or the
361 option is specified, all existing slice entries will be cleared
362 (marked as unused), and these "p" lines will have to be used to
363 explicitly set slice information. If multiple slices need to be
364 set, multiple "p" lines must be specified; one for each slice.
366 These slice lines must occur after any geometry specification lines,
373 slices. Specifying a slice type of zero is
374 the same as clearing the slice and marking it as unused; however,
375 dummy values (such as "0") must still be specified for
380 Note: the start offset will be rounded upwards to a head boundary if
381 necessary, and the end offset will be rounded downwards to a cylinder
382 boundary if necessary.
384 Example: to clear slice 4 and mark it as unused:
385 .Bd -literal -offset indent
389 Example: to set slice 1 to a
391 slice, starting at sector 1
392 for 2503871 sectors (note: these numbers will be rounded upwards and
393 downwards to correspond to head and cylinder boundaries):
395 .Bd -literal -offset indent
405 the active slice. Can occur anywhere in the config file, but only
408 Example: to make slice 1 the active slice:
409 .Bd -literal -offset indent
414 .Bl -tag -width /boot/mbr -compact
416 The default boot code
423 The default boot code will not necessarily handle all slice types
424 correctly, in particular those introduced since MS-DOS 6.x.
426 The entire program should be made more user-friendly.
430 do not understand the difference between
434 causing difficulty to adjust.
436 You cannot use this command to completely dedicate a disk to
440 command must be used for this.
nant's projects / dragonfly.git / blob