173 lines
5.1 KiB
Groff
173 lines
5.1 KiB
Groff
.\" $Id: fdisk.8,v 1.7 1994/09/23 05:30:09 mycroft Exp $ -*- nroff -*-
|
|
.Dd April 4, 1993
|
|
.Dt FDISK 8
|
|
.\" .Os BSD 4
|
|
.Sh NAME
|
|
.Nm fdisk
|
|
.Nd DOS partition maintenance program
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl aiu
|
|
.Op Ar device
|
|
.Sh PROLOGUE
|
|
In order for the BIOS to boot the kernel, certain conventions must be
|
|
adhered to.
|
|
Sector 0 of the disk must contain boot code, a partition table, and a
|
|
magic number.
|
|
BIOS partitions can be used to break the disk up into several pieces.
|
|
The BIOS brings in sector 0, verifies the magic number, and begins
|
|
executing the code at the first byte.
|
|
This code is turn searches the DOS partition table for an `active'
|
|
partition.
|
|
If one is found, the boot block from that partition is loaded and replaces
|
|
the original boot block.
|
|
Under DOS, you could have one or more partitions with one active.
|
|
The DOS
|
|
.Nm
|
|
program can be used to divide space on the disk into partitions and set
|
|
one active.
|
|
.Pp
|
|
The NetBSD program
|
|
.Nm
|
|
serves a similar purpose to the DOS program.
|
|
When called with no arguments, it prints the sector 0 partition table.
|
|
An example follows:
|
|
.Bd -literal
|
|
******* Working on device /dev/rwd0d *******
|
|
parameters extracted from in-core disklabel are:
|
|
cylinders=769 heads=15 sectors/track=33 (495 sectors/cylinder)
|
|
|
|
parameters to be used for BIOS calculations are:
|
|
cylinders=769 heads=15 sectors/track=33 (495 sectors/cylinder)
|
|
|
|
Warning: BIOS sector numbering starts with sector 1
|
|
Information from DOS bootblock is:
|
|
The data for partition 0 is:
|
|
sysid 165 (NetBSD)
|
|
start 495, size 380160 (185 MB), flag 0
|
|
beg: cylinder 1, head 0, sector 1
|
|
end: cylinder 768, head 14, sector 33
|
|
The data for partition 1 is:
|
|
sysid 164 (unknown)
|
|
start 378180, size 2475 (1 MB), flag 0
|
|
beg: cylinder 764, head 0, sector 1
|
|
end: cylinder 768, head 14, sector 33
|
|
The data for partition 2 is:
|
|
<UNUSED>
|
|
The data for partition 3 is:
|
|
sysid 99 (ISC UNIX, other System V/386, GNU HURD or Mach)
|
|
start 380656, size 224234 (109 MB), flag 80
|
|
beg: cylinder 769, head 0, sector 2
|
|
end: cylinder 197, head 14, sector 33
|
|
.Ed
|
|
.Pp
|
|
The disk is divided into three partitions that happen to fill the disk.
|
|
The second partition overlaps the end of the first.
|
|
(Used for debugging purposes)
|
|
.Bl -tag -width "cyl, sector and head"
|
|
.It Em "sysid"
|
|
is used to label the partition. NetBSD reserves the
|
|
magic number 165 decimal (A5 in hex).
|
|
.It Em "start and size"
|
|
fields provide the start address
|
|
and size of a partition in sectors.
|
|
.It Em "flag 80"
|
|
specifies that this is the active partition.
|
|
.It Em "cyl, sector and head"
|
|
fields are used to specify the beginning address
|
|
and end address for the partition.
|
|
.It Em "Note:"
|
|
these numbers are calculated using BIOS's understanding of the disk geometry
|
|
and saved in the bootblock.
|
|
.El
|
|
.Pp
|
|
The flags
|
|
.Fl i
|
|
or
|
|
.Fl u
|
|
are used to indicate that the partition data is to be updated.
|
|
The
|
|
.Nm
|
|
program will enter a conversational mode.
|
|
This mode is designed not to change any data unless you explicitly tell it to;
|
|
.Nm
|
|
selects defaults for its questions to guarantee that behavior.
|
|
.Pp
|
|
It displays each partition and asks if you want to edit it.
|
|
If you reply affirmatively,
|
|
it will step through each field showing the old value
|
|
and asking for a new one.
|
|
When you are done with a partition,
|
|
.Nm
|
|
will display the information again and ask if it is correct.
|
|
.Nm
|
|
will then procede to the next entry.
|
|
.Pp
|
|
Getting the
|
|
.Em cyl, sector,
|
|
and
|
|
.Em head
|
|
fields correct is tricky.
|
|
So by default,
|
|
they will be calculated for you;
|
|
you can specify them if you choose.
|
|
.Pp
|
|
After all the partitions are processed,
|
|
you are given the option to change the
|
|
.Em active
|
|
partition.
|
|
To change only the
|
|
.Em active
|
|
partition, you can use the
|
|
.Fl a
|
|
flag instead.
|
|
.Pp
|
|
Finally,
|
|
when the all the data for the first sector has been accumulated,
|
|
.Nm
|
|
will ask if you really want to rewrite sector 0.
|
|
Only if you reply affirmatively to this question will
|
|
.Nm
|
|
write anything to the disk.
|
|
.Pp
|
|
The difference between the
|
|
.Fl u
|
|
flag and
|
|
.Fl i
|
|
flag is that
|
|
the
|
|
.Fl u
|
|
flag just edits the fields as they appear on the disk, while the
|
|
.Fl i
|
|
flag is used to `initialize' sector 0.
|
|
The
|
|
.Fl i
|
|
flag instructs
|
|
.Nm
|
|
to start by making the first 3 partitions empty, setting the last partition
|
|
to use the whole disk for NetBSD, and marking the last partition active.
|
|
.Sh NOTES
|
|
The automatic calculation of starting cylinder etc. uses
|
|
a set of figures that represent what the BIOS thinks is the
|
|
geometry of the drive.
|
|
These figures are by default taken from the incore disklabel, but
|
|
.Nm
|
|
gives you an opportunity to change them.
|
|
This allows the user to create a bootblock that can work with drives
|
|
that use geometry translation under the BIOS.
|
|
.Pp
|
|
If you hand craft your disk layout,
|
|
please make sure that the NetBSD partition starts on a cylinder boundary.
|
|
(This restriction may be changed in the future.)
|
|
.Pp
|
|
Editing an existing partition is risky, and may cause you to
|
|
lose all the data in that partition.
|
|
.Pp
|
|
You should run this program interactively once or twice to see how it works.
|
|
This is completely safe as long as you answer the last question in the negative.
|
|
.Sh SEE ALSO
|
|
.Xr disklabel 8
|
|
.Sh BUGS
|
|
There are subtleties that the program detects that are not explained in
|
|
this manual page.
|