8 .Nd PC slice table maintenance utility
20 In order for the BIOS to boot the kernel,
21 certain conventions must be adhered to.
22 Sector 0 of the disk must contain boot code,
25 BIOS slices can be used to break the disk up into several pieces.
26 The BIOS brings in sector 0 and verifies the magic number.
28 0 boot code then searches the slice table to determine which
31 This boot code then brings in the bootstrap from the
32 active slice and, if marked bootable, runs it.
35 you can have one or more slices with one active.
39 utility can be used to divide space on the disk into slices and set one
46 serves a similar purpose to the
49 The first form is used to
50 display slice information or to interactively edit the slice
52 The second is used to write a slice table using a
54 and is designed to be used by other scripts/programs.
57 .Bl -tag -width indent
59 Change the active slice only.
64 Get the boot code from the file
69 Reinitialize the boot code contained in sector 0 of the disk.
73 .It Fl f Ar configfile
74 Set slice values using the file
78 always modifies existing slices, unless
80 is also given, in which case all existing slices are deleted (marked
90 in which case standard input is read.
92 .Sx CONFIGURATION FILE ,
93 below, for file syntax.
98 is used, you are not asked if you really want to write the slices
99 table (as you are in the interactive mode).
102 Initialize sector 0 of the disk.
109 Initialize the contents of sector 0
112 slice covering the entire disk.
114 Print summary information and exit.
116 Test mode; do not write slice values.
117 Generally used with the
119 option to see what would be written to the slice table.
123 Is used for updating (editing) sector 0 of the disk.
133 prints out the slice table that is written to the disk.
135 Operate on a single slice table entry only.
141 The final disk name can be provided as a
143 disk name only, e.g.\&
145 or as a full pathname.
148 tries to figure out the default disk device name from the
151 When called with no arguments, it prints the sector 0 slice table.
154 ******* Working on device /dev/ad0 *******
155 parameters extracted from in-core disklabel are:
156 cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
158 parameters to be used for BIOS calculations are:
159 cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
161 Warning: BIOS sector numbering starts with sector 1
162 Information from DOS bootblock is:
163 The data for partition 1 is:
164 sysid 165,(FreeBSD/NetBSD/386BSD)
165 start 495, size 380160 (185 Meg), flag 0
166 beg: cyl 1/ sector 1/ head 0;
167 end: cyl 768/ sector 33/ head 14
168 The data for partition 2 is:
170 start 378180, size 2475 (1 Meg), flag 0
171 beg: cyl 764/ sector 1/ head 0;
172 end: cyl 768/ sector 33/ head 14
173 The data for partition 3 is:
175 The data for partition 4 is:
176 sysid 99,(ISC UNIX, other System V/386, GNU HURD or Mach)
177 start 380656, size 224234 (109 Meg), flag 80
178 beg: cyl 769/ sector 2/ head 0;
179 end: cyl 197/ sector 33/ head 14
182 The disk is divided into three slices that happen to fill the disk.
183 The second slice overlaps the end of the first.
184 (Used for debugging purposes.)
185 .Bl -tag -width ".Em cyl , sector No and Em head"
187 is used to label the slice.
190 magic number 165 decimal (A5 in hex).
196 fields provide the start address
197 and size of a slice in sectors.
199 specifies that this is the active slice.
205 fields are used to specify the beginning and end addresses of the slice.
209 these numbers are calculated using BIOS's understanding of the disk geometry
210 and saved in the bootblock.
216 flags are used to indicate that the slice data is to be updated.
219 option is also given,
221 will enter a conversational mode.
222 In this mode, no changes will be written to disk unless you explicitly tell
228 utility will display each slice and ask whether you want to edit it.
231 will step through each field, show you the old value,
232 and ask you for a new one.
233 When you are done with the slice,
235 will display it and ask you whether it is correct.
236 It will then proceed to the next entry.
242 fields correct is tricky, so by default,
243 they will be calculated for you;
244 you can specify them if you choose to though.
246 After all the slices are processed,
247 you are given the option to change the
250 Finally, when all the new data for sector 0 has been accumulated,
251 you are asked to confirm whether you really want to rewrite it.
253 The difference between the
260 flag just edits (updates) the fields as they appear on the disk,
266 it will set up the last BIOS slice to use the whole disk for
270 The automatic calculation of starting cylinder etc. uses
271 a set of figures that represent what the BIOS thinks the
272 geometry of the drive is.
273 These figures are taken from the in-core disklabel by default,
276 initially gives you an opportunity to change them.
277 This allows you to create a bootblock that can work with drives
278 that use geometry translation under the BIOS.
280 If you hand craft your disk layout,
281 please make sure that the
283 slice starts on a cylinder boundary.
284 A number of decisions made later may assume this.
285 (This might not be necessary later.)
287 Editing an existing slice will most likely result in the loss of
288 all data in that slice.
292 interactively once or twice to see how it works.
293 This is completely safe as long as you answer the last question
295 There are subtleties that
297 detects that are not fully explained in this manual page.
298 .Sh CONFIGURATION FILE
301 option is given, a disk's slice table can be written using values
304 The syntax of this file is very simple;
305 each line is either a comment or a specification, as follows:
306 .Bl -tag -width indent
307 .It Ic # Ar comment ...
308 Lines beginning with a
310 are comments and are ignored.
311 .It Ic g Ar spec1 spec2 spec3
312 Set the BIOS geometry used in slice calculations.
314 three values specified, with a letter preceding each number:
315 .Bl -tag -width indent
317 Set the number of cylinders to
320 Set the number of heads to
323 Set the number of sectors/track to
327 These specs can occur in any order, as the leading letter determines
328 which value is which; however, all three must be specified.
330 This line must occur before any lines that specify slice
333 It is an error if the following is not true:
334 .Bd -literal -offset indent
335 1 <= number of cylinders
336 1 <= number of heads <= 256
337 1 <= number of sectors/track < 64
340 The number of cylinders should be less than or equal to 1024, but this
341 is not enforced, although a warning will be printed.
346 filesystem) must lie completely within the
347 first 1024 cylinders; if this is not true, booting may fail.
348 Non-bootable slices do not have this restriction.
350 Example (all of these are equivalent), for a disk with 1019 cylinders,
351 39 heads, and 63 sectors:
352 .Bd -literal -offset indent
357 .It Ic p Ar slice type start length
358 Set the slice given by
368 Only those slices explicitly mentioned by these lines are modified;
369 any slice not referenced by a
371 line will not be modified.
372 However, if an invalid slice table is present, or the
374 option is specified, all existing slice entries will be cleared
375 (marked as unused), and these
377 lines will have to be used to
378 explicitly set slice information.
379 If multiple slices need to be
382 lines must be specified; one for each slice.
384 These slice lines must occur after any geometry specification lines,
392 Specifying a slice type of zero is
393 the same as clearing the slice and marking it as unused; however,
394 dummy values (such as
396 must still be specified for
401 Note: the start offset will be rounded upwards to a head boundary if
402 necessary, and the end offset will be rounded downwards to a cylinder
403 boundary if necessary.
405 Example: to clear slice 4 and mark it as unused:
409 Example: to set slice 1 to a
411 slice, starting at sector 1
412 for 2503871 sectors (note: these numbers will be rounded upwards and
413 downwards to correspond to head and cylinder boundaries):
415 .Dl "p 1 165 1 2503871"
421 Can occur anywhere in the config file, but only
424 Example: to make slice 1 the active slice:
429 .Bl -tag -width ".Pa /boot/mbr" -compact
431 The default boot code.
438 The default boot code will not necessarily handle all slice types
439 correctly, in particular those introduced since
443 The entire utility should be made more user-friendly.
447 do not understand the difference between
451 causing difficulty to adjust.
453 You cannot use this command to completely dedicate a disk to
457 command must be used for this.
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