path: root/sbin/fdisk/fdisk.8

.\"	$OpenBSD: fdisk.8,v 1.118 2023/05/07 13:03:03 krw Exp $
.\"
.\"
.\" Copyright (c) 1997 Tobias Weingartner
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: May 7 2023 $
.Dt FDISK 8
.Os
.Sh NAME
.Nm fdisk
.Nd partition table maintenance program
.Sh SYNOPSIS
.Nm fdisk
.Op Fl evy
.Op Fl A  | g | i | u
.Op Fl b Ar blocks Ns Op @ Ns Ar offset Ns Op : Ns Ar type
.Op Fl l Ar blocks | Fl c Ar cylinders Fl h Ar heads Fl s Ar sectors
.Op Fl f Ar file
.Ar disk
.Sh DESCRIPTION
.Nm fdisk
creates and edits MBR and GPT partition tables.
These tables are used by the boot process of some
platforms to find the
.Ox
kernel and, when present, are used by the kernel to find the
.Xr disklabel 5 .
.Pp
Caution is advised when editing these tables since some platforms
rely on specific configurations created at install time.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl A
Modifies the GPT partition table entries on
.Ar disk
to put all available space not taken by
.Fl b
into a single
.Ox
partition.
The available space is maximized by deleting all existing partition
entries except for partition types APFS ISC, APFS, APFS Recovery, BIOS Boot,
HiFive FSBL, HiFive BBL and partitions with the
.Sq Required
GPT attribute set.
.Pp
If
APFS ISC, APFS, or APFS Recovery
partitions are detected then existing
EFI system
partitions are also preserved.
If the preserved EFI system partition has fewer blocks
than the number requested with
.Fl b ,
the modified GPT is discarded.
.It Fl b Ar blocks Ns Op @ Ns Ar offset Ns Op : Ns Ar type
Creates a partition table entry of the specified number of blocks, offset
and type.
.Ar offset
defaults to the first available block, and
.Ar type
defaults to
.Sq EF .
.Pp
.Fl b
is only available in combination with
.Fl A ,
.Fl g ,
or
.Fl i .
.Pp
If
.Fl A
or
.Fl g
is specified, only the
.Ar blocks
value is used.
.It Xo
.Fl c Ar cylinders
.Fl h Ar heads
.Fl s Ar sectors
.Xc
Specifies a geometry for
.Nm
to use.
By default the disk size and geometry are obtained
from the default
.Xr disklabel 5
constructed by the kernel for
.Ar disk .
See
.Xr disklabel 5
and
.Xr disklabel 8 .
.It Fl e
Invokes the interactive partition table editor.
See
.Sx COMMAND MODE
below.
.It Fl f Ar file
Specifies a file containing the bootcode for an MBR.
The default file is
.Pa /usr/mdec/mbr .
.It Fl g
Writes a default GPT, including a protective MBR, to
.Ar disk .
The GPT has a single
.Ox
partition containing all available space not taken by
.Fl b .
.It Fl i
Writes a default MBR to
.Ar disk .
The MBR has a single
.Ox
partition containing all the available space not taken by
.Fl b .
The bootcode is initialized as described in
.Fl u .
.It Fl l Ar count
Treat
.Ar disk
as though it has a size of
.Ar count
blocks.
.It Fl u
Updates the MBR bootcode.
If a bootcode file is present (see
.Fl f )
the MBR, except for the partition entries, is replaced by
the first block of the file.
If no bootcode file is present, zeros are used.
.Pp
Not available when editing a GPT.
.It Fl v
Prints detailed information about the MBR, the Primary GPT and the
Secondary GPT.
.It Fl y
New or modified partition table is written to disk without
asking for confirmation.
.It Ar disk
.Nm
creates or modifies the partition table of
.Ar disk .
.Ar disk
can be a full pathname,
e.g.
.Pa /dev/rsd0c ,
a raw partition name, e.g.
.Pa sd0c ,
or just the disk name, e.g.
.Pa sd0 .
.El
.Sh TYPICAL LAYOUT
When called without options
.Nm
prints the partition table of
.Ar disk .
.Pp
If
.Ar disk
has a GPT a terse version of its contents is printed:
.Bd -literal -offset 1n
# fdisk sd0
Disk: sd0       Usable LBA: 64 to 500118128 [500118192 Sectors]
   #: type                                 [       start:         size ]
------------------------------------------------------------------------
   1: EFI Sys                              [          64:          960 ]
   3: OpenBSD                              [        1024:    500117105 ]
.Ed
.Pp
When
.Ar disk
does not have a GPT, the first block of
.Ar disk
is printed as an MBR:
.Bd -literal -offset 1n
# fdisk sd0
Disk: sd0      geometry: 121601/255/63 [1953525168 Sectors]
Offset: 0      Signature: 0xAA55
           Starting       Ending      LBA Info:
 #: id     C  H  S -      C   H  S [     start:       size ]
------------------------------------------------------------------------
 0: 0B     0  1  1 -  26108   0 63 [        63:  419425020 ] FAT32
 1: 00     0  0  0 -      0   0  0 [         0:          0 ] unused
 2: 00     0  0  0 -      0   0  0 [         0:          0 ] unused
*3: A6 26108  1  1 - 121600 254 63 [ 419425083: 1534094982 ] OpenBSD
.Ed
.Pp
.Em NOTE :
Partition entry #3 of this MBR is flagged as bootable.
.Pp
.Em NOTE :
The
.Em S
field in the C/H/S values is
.Dq 1 based ,
but the LBA "start" field is
.Dq 0 based .
.Pp
The
.Fl v
option causes more information to be printed:
.Bd -literal -offset 1n
# fdisk -v sd0
Primary GPT:
Disk: sd0       Usable LBA: 64 to 500118128 [500118192 Sectors]
GUID: f0418899-4976-4604-a783-3ebe135a8f12
   #: type                                 [       start:         size ]
      guid                                 name
------------------------------------------------------------------------
   1: EFI Sys                              [          64:          960 ]
      d0834013-dab8-44df-a5e4-123148f17e03 EFI System Area
   3: OpenBSD                              [        1024:    500117105 ]
      cd356d77-8369-44b4-996e-79e8b9a47bfe OpenBSD Area

Secondary GPT:
Disk: sd0       Usable LBA: 64 to 500118128 [500118192 Sectors]
GUID: f0418899-4976-4604-a783-3ebe135a8f12
   #: type                                 [       start:         size ]
      guid                                 name
------------------------------------------------------------------------
   1: EFI Sys                              [          64:          960 ]
      d0834013-dab8-44df-a5e4-123148f17e03 EFI System Area
   3: OpenBSD                              [        1024:    500117105 ]
      cd356d77-8369-44b4-996e-79e8b9a47bfe OpenBSD Area

MBR:
Disk: sd0       geometry: 31130/255/63 [500118192 Sectors]
Offset: 0       Signature: 0xAA55
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
 0: EE      0   0   2 -  31130 233  63 [           1:   500118191 ] EFI GPT
 1: 00      0   0   0 -      0   0   0 [           0:           0 ] unused
 2: 00      0   0   0 -      0   0   0 [           0:           0 ] unused
 3: 00      0   0   0 -      0   0   0 [           0:           0 ] unused
.Ed
.Sh COMMAND MODE
When
.Nm
enters interactive command mode
it copies the partition table from
.Ar disk
into memory and performs all edits on
that copy.
The partition table on
.Ar disk
is modified only by
.Em write
or
.Em quit
commands.
.Pp
The prompt contains information about the state of the edit
process.
.Pp
.Dl Ar disk Ns *:1>
.Pp
Where
.Ar disk
is the name of the disk being edited,
.Sq *
means that the partition table has been modified, but
not yet written to disk and
1 is the edit level when operating on the MBR or GPT.
This number is 2 when editing an extended partition in the MBR,
3 when editing an extended partition within the edit level 2
extended partition, and so on.
.Pp
The list of commands and their functions is
given below.
Commands may be abbreviated.
The first command matching the abbreviation is selected.
.Bl -tag -width Ds
.It Cm ?\&
A synonym for
.Cm help .
.It Cm help
Displays a short summary of available commands.
.It Cm manual
Displays this manual page.
.It Cm reinit Op Cm gpt | Cm mbr
Initializes the partition table.
.Pp
By default an MBR partition table is initialized.
If
.Cm gpt
is specified a GPT partition table is initialized, including the
protective MBR.
.It Cm setpid Ar #
Sets the identifier of the partition table entry.
.It Cm edit Ar #
Edit an entry in the partition table.
The offset and size of the entry may be specified in CHS mode (MBR only),
by using sector offsets and sizes, or by using
the units
.Sq b ,
.Sq k ,
.Sq m ,
.Sq g ,
or
.Sq t
to indicate bytes, kilobytes, megabytes, gigabytes, or terabytes.
The special size value
.Sq *
causes the partition to be sized to use the remainder of the disk.
.It Cm flag Ar # Op Ar value
Sets the partition entry's flag value.
If
.Ar value
is not provided the partition entry is flagged as being bootable
and all other partition entries are flagged as not bootable.
Partition entries flagged as bootable are printed with a
.Sq *
prefix.
.Pp
If
.Ar value
is provided the partition entry's flag value is set to
.Ar value
and no other partition entry is modified.
A
.Ar value
of 0 is used to clear the bootable flag.
.It Cm update
Updates the MBR bootcode.
If a bootcode file is present (see
.Fl f )
the MBR, except for the partition entries, is replaced by
the first block of the file.
If no bootcode file is present, zeros are used.
.Pp
Not available when editing a GPT.
.It Cm select Ar #
Selects an extended partition entry, increasing the edit level by 1.
.Pp
Not available when editing a GPT.
.It Cm swap Ar # Ar #
Swaps two partition entries.
.It Cm print Op Ar unit
Prints the partition table.
If
.Ar unit
is
.Sq b ,
.Sq k ,
.Sq m ,
.Sq g ,
or
.Sq t
partition sizes are shown in bytes,
kilobytes, megabytes, gigabytes, or terabytes.
If
.Ar unit
is not provided, sizes are shown in sectors.
.It Cm write
Writes the partition table to disk.
.It Cm exit
Discards outstanding changes and exits the current edit level.
If the edit level is 1,
.Nm
terminates.
.It Cm quit
Writes outstanding changes to disk and exits the current edit
level.
If the edit level is 1,
.Nm
terminates.
.It Cm abort
Discards outstanding changes and terminates
.Nm .
.El
.Sh FILES
.Bl -tag -width /usr/mdec/mbr -compact
.It Pa /usr/mdec/mbr
default MBR bootcode
.El
.Sh SEE ALSO
.Xr disklabel 5 ,
.Xr boot 8 ,
.Xr boot_amd64 8 ,
.Xr boot_i386 8 ,
.Xr boot_macppc 8 ,
.Xr disklabel 8