freebsd-dev/sbin/fdisk_pc98/fdisk.8

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.\" $FreeBSD$
.\"
.Dd April 30, 2007
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.Dt FDISK 8
.Os
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.Sh NAME
.Nm fdisk
.Nd NEC PC-98x1 slice table maintenance utility
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.Sh SYNOPSIS
.Nm
.Op Fl BIaistuv
.Op Fl 12345678
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.Op Ar disk
.Nm
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.Fl f Ar configfile
.Op Fl itv
.Op Ar disk
.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 slice table,
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and a magic number.
BIOS slices can be used to break the disk up into several pieces.
The BIOS brings in sector 0 and verifies the magic number.
The sector
0 boot code then searches the slice table to determine which
slice is marked
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.Dq active .
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This boot code then brings in the bootstrap from the
active slice and, if marked bootable, runs it.
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Under
.Tn DOS ,
you can have one or more slices with one active.
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The
.Tn DOS
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.Nm
utility can be used to divide space on the disk into slices and set one
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active.
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.Sh DESCRIPTION
The
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.Fx
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utility,
.Nm ,
serves a similar purpose to the
.Tn DOS
utility.
The first form is used to
display slice information or to interactively edit the slice
table.
The second is used to write a slice table using a
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.Ar configfile ,
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and is designed to be used by other scripts/programs.
.Pp
Options are:
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.Bl -tag -width indent
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.It Fl a
Change the active slice only.
Ignored if
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.Fl f
is given.
.It Fl B
Reinitialize the boot code contained in sector 0 of the disk.
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Ignored if
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.Fl f
is given.
.It Fl f Ar configfile
Set slice values using the file
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.Ar configfile .
The
.Ar configfile
always modifies existing slices, unless
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.Fl i
is also given, in which case all existing slices are deleted (marked
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as
.Dq unused )
before the
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.Ar configfile
is read.
The
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.Ar configfile
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can be
.Sq Fl ,
in which case standard input is read.
See
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.Sx CONFIGURATION FILE ,
below, for file syntax.
.Pp
.Em WARNING :
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when
.Fl f
is used, you are not asked if you really want to write the slices
table (as you are in the interactive mode).
Use with caution!
.It Fl i
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Initialize sector 0 of the disk.
This implies
.Fl u ,
unless
.Fl f
is given.
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.It Fl I
Initialize sector 0 slice table
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for one
.Fx
slice covering the entire disk.
Some space at the start of the disk will reserved for the IPL program
and the pc98 slice table itself.
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.It Fl s
Print summary information and exit.
.It Fl t
Test mode; do not write slice values.
Generally used with the
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.Fl f
option to see what would be written to the slice table.
Implies
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.Fl v .
.It Fl u
Update (edit) the disk's sector 0 slice table.
Ignored if
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.Fl f
is given.
.It Fl v
Be verbose.
Slices that are unused are suppressed unless this flag is specified.
When
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.Fl f
is used,
.Nm
prints out the slice table that is written to the disk.
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.It Fl 12345678
Operate on a single slice table entry only.
Ignored if
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.Fl f
is given.
.El
.Pp
The final disk name can be provided as a
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.Dq bare
disk name only, e.g.\&
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.Pa da0 ,
or as a full pathname.
If omitted,
.Nm
tries to figure out the default disk device name from the
mounted root device.
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.Pp
When called with no arguments, it prints the sector 0 slice table.
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An example follows:
.Bd -literal
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******* Working on device /dev/da0 *******
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parameters extracted from in-core disklabel are:
cylinders=33075 heads=8 sectors/track=32 (256 blks/cyl)
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parameters to be used for BIOS calculations are:
cylinders=33075 heads=8 sectors/track=32 (256 blks/cyl)
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Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysmid 148,(FreeBSD/NetBSD/386BSD)
start 256, size 2490112 (1215 Meg), sid 196
beg: cyl 1/ sector 0/ head 0;
end: cyl 9727/ sector 0/ head 0
system Name FreeBSD(98)
The data for partition 2 is:
sysmid 148,(FreeBSD/NetBSD/386BSD)
start 2490368, size 5505024 (2688 Meg), sid 196
beg: cyl 9728/ sector 0/ head 0;
end: cyl 31231/ sector 0/ head 0
system Name FreeBSD(98)
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
The data for partition 5 is:
<UNUSED>
The data for partition 6 is:
<UNUSED>
The data for partition 7 is:
<UNUSED>
The data for partition 8 is:
<UNUSED>
The data for partition 9 is:
<UNUSED>
The data for partition 10 is:
<UNUSED>
The data for partition 11 is:
<UNUSED>
The data for partition 12 is:
<UNUSED>
The data for partition 13 is:
<UNUSED>
The data for partition 14 is:
<UNUSED>
The data for partition 15 is:
<UNUSED>
The data for partition 16 is:
<UNUSED>
.Ed
.Pp
The disk is divided into three slices that happen to fill the disk.
The second slice overlaps the end of the first.
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(Used for debugging purposes.)
.Bl -tag -width ".Em cyl , sector No and Em head"
.It Em sysmid
is used to label the slice.
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.Fx
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reserves the
magic number 148 decimal (94 in hex).
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.It Xo
.Em start
and
.Em size
.Xc
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fields provide the start address
and size of a slice in sectors.
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.It Xo
.Em cyl , sector
and
.Em head
.Xc
fields are used to specify the beginning and end addresses of the slice.
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.It Em "system Name"
is the name of the slice.
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.El
.Pp
.Em Note :
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these numbers are calculated using BIOS's understanding of the disk geometry
and saved in the bootblock.
.Pp
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The
.Fl i
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and
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.Fl u
flags are used to indicate that the slice data is to be updated.
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Unless the
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.Fl f
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option is also given,
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.Nm
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will enter a conversational mode.
In this mode, no changes will be written to disk unless you explicitly tell
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.Nm
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to.
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.Pp
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The
.Nm
utility will display each slice and ask whether you want to edit it.
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If you say yes,
.Nm
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will step through each field, show you the old value,
and ask you for a new one.
When you are done with the slice,
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.Nm
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will display it and ask you whether it is correct.
It will then proceed to the next entry.
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.Pp
Getting the
.Em cyl , sector ,
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and
.Em head
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fields correct is tricky, so by default,
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they will be calculated for you;
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you can specify them if you choose to though.
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.Pp
After all the slices are processed,
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you are given the option to change the
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.Dq active
slice.
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Finally, when all the new data for sector 0 has been accumulated,
you are asked to confirm whether you really want to rewrite it.
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.Pp
The difference between the
.Fl u
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and
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.Fl i
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flags is that
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the
.Fl u
flag edits (updates) the existing slice parameters
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while the
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.Fl i
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flag is used to
.Dq initialize
them (old values will be ignored);
it will setup the last BIOS slice to use the whole disk for
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.Fx ;
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and make it active.
.Sh NOTES
The automatic calculation of starting cylinder etc.\& uses
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a set of figures that represent what the BIOS thinks the
geometry of the drive is.
These figures are taken from the in-core disklabel by default,
but
.Nm
initially gives you an opportunity to change them.
This allows you to create a bootblock that can work with drives
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that use geometry translation under the BIOS.
.Pp
If you hand craft your disk layout,
please make sure that the
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.Fx
slice starts on a cylinder boundary.
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.Pp
Editing an existing slice will most likely result in the loss of
all data in that slice.
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.Pp
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You should run
.Nm
interactively once or twice to see how it works.
This is completely safe as long as you answer the last question
in the negative.
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There are subtleties that
.Nm
detects that are not fully explained in this manual page.
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.Sh CONFIGURATION FILE
When the
.Fl f
option is given, a disk's slice table can be written using values
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from a
.Ar configfile .
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The syntax of this file is very simple;
each line is either a comment or a specification, as follows:
.Bl -tag -width indent
.It Ic # Ar comment ...
Lines beginning with a
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.Ic #
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are comments and are ignored.
.It Ic g Ar spec1 spec2 spec3
Set the BIOS geometry used in slice calculations.
There must be
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three values specified, with a letter preceding each number:
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.Bl -tag -width indent
.It Cm c Ns Ar num
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Set the number of cylinders to
.Ar num .
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.It Cm h Ns Ar num
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Set the number of heads to
.Ar num .
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.It Cm s Ns Ar num
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Set the number of sectors/track to
.Ar num .
.El
.Pp
These specs can occur in any order, as the leading letter determines
which value is which; however, all three must be specified.
.Pp
This line must occur before any lines that specify slice
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information.
.Pp
It is an error if the following is not true:
.Bd -literal -offset indent
1 <= number of cylinders
1 <= number of heads <= 256
1 <= number of sectors/track < 64
.Ed
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.Pp
The number of cylinders should be less than or equal to 1024, but this
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is not enforced, although a warning will be printed.
Note that bootable
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.Fx
slices (the
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.Dq Pa /
file system) must lie completely within the
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first 1024 cylinders; if this is not true, booting may fail.
Non-bootable slices do not have this restriction.
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.Pp
Example (all of these are equivalent), for a disk with 1019 cylinders,
39 heads, and 63 sectors:
.Bd -literal -offset indent
g c1019 h39 s63
g h39 c1019 s63
g s63 h39 c1019
.Ed
.It Ic p Ar slice type start length
Set the slice given by
.Ar slice
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(1-8) to type
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.Ar type ,
starting at sector
.Ar start
for
.Ar length
sectors.
.Pp
Only those slices explicitly mentioned by these lines are modified;
any slice not referenced by a
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.Ic p
line will not be modified.
However, if an invalid slice table is present, or the
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.Fl i
option is specified, all existing slice entries will be cleared
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(marked as unused), and these
.Ic p
lines will have to be used to
explicitly set slice information.
If multiple slices need to be
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set, multiple
.Ic p
lines must be specified; one for each slice.
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.Pp
These slice lines must occur after any geometry specification lines,
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if one is present.
.Pp
The
.Ar type
is 165 for
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.Fx
slices.
Specifying a slice type of zero is
the same as clearing the slice and marking it as unused; however,
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dummy values (such as
.Dq 0 )
must still be specified for
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.Ar start
and
.Ar length .
.Pp
Note: the start offset will be rounded upwards to a head boundary if
necessary, and the end offset will be rounded downwards to a cylinder
boundary if necessary.
.Pp
Example: to clear slice 4 and mark it as unused:
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.Pp
.Dl "p 4 0 0 0"
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.Pp
Example: to set slice 1 to a
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.Fx
slice, starting at sector 1
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for 2503871 sectors (note: these numbers will be rounded upwards and
downwards to correspond to head and cylinder boundaries):
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.Pp
.Dl "p 1 165 1 2503871"
.It Ic a Ar slice
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Make
.Ar slice
the active slice.
Can occur anywhere in the config file, but only
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one must be present.
.Pp
Example: to make slice 1 the active slice:
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.Pp
.Dl "a 1"
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.El
.Sh SEE ALSO
.Xr boot98cfg 8 ,
.Xr bsdlabel 8 ,
.Xr gpart 8 ,
.Xr newfs 8
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.Sh BUGS
The default boot code will not necessarily handle all slice types
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correctly, in particular those introduced since
.Tn MS-DOS
6.x.
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.Pp
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The entire utility should be made more user-friendly.
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.Pp
Most users new to
.Fx
do not understand the difference between
.Dq slice
and
.Dq partition ,
causing difficulty to adjust.
.Pp
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You cannot use this command to completely dedicate a disk to
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.Fx .
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The
.Xr bsdlabel 8
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command must be used for this.