FDISK(8) Maintenance Commands and Procedures FDISK(8)

NAME

fdisk - create or modify fixed disk partition table

SYNOPSIS

fdisk [-o offset] [-s size] [-P fill_patt] [-S geom_file]
[-w | -r | -d | -n | -I | -B | -t | -T | -g | -G | -R]
[--F fdisk_file] [ [-v] -W {fdisk_file | -}]
[-h] [-b masterboot]
[-A id : act : bhead : bsect : bcyl : ehead : esect :
ecyl : rsect : numsect]
[-D id : act : bhead: bsect : bcyl : ehead: esect :
ecyl : rsect : numsect] rdevice
[-E [slot : active]]
rdevice

DESCRIPTION

This command is used to do the following:

o Create and modify an fdisk partition table on x86 systems

o Create and modify an fdisk partition table on removable
media on SPARC or x86 systems

o Install the master boot record that is put in the first
sector of the fixed disk on x86 systems only


This table is used by the first-stage bootstrap (or firmware) to
identify parts of the disk reserved for different operating systems,
and to identify the partition containing the second-stage bootstrap
(the active Solaris partition). The rdevice argument must be used to
specify the raw device associated with the fixed disk, for example,
/dev/rdsk/c0t0d0p0.


The program can operate in three different modes. The first is
interactive mode. In interactive mode, the program displays the
partition table as it exists on the disk, and then presents a menu
allowing the user to modify the table. The menu, questions, warnings,
and error messages are intended to be self-explanatory.


In interactive mode, if there is no partition table on the disk, the
user is given the options of creating a default partitioning or
specifying the initial table values. The default partitioning
allocates the entire disk for the Solaris system and makes the
Solaris system partition active. In either case, when the initial
table is created, fdisk also writes out the first-stage bootstrap
(x86 only) code along with the partition table. In this mode, (x86
only) when creating an entry for a non-EFI partition on a disk that
is larger than 2 TB (terabytes), fdisk warns that the maximum size of
the partition is 2 TB. Under these conditions percentages displayed
by fdisk are based on 2 TB.


The second mode of operation is used for automated entry addition,
entry deletion, or replacement of the entire fdisk table. This mode
can add or delete an entry described on the command line. In this
mode the entire fdisk table can be read in from a file replacing the
original table. fdisk can also be used to create this file. There is
a command line option that will cause fdisk to replace any fdisk
table with the default of the whole disk for the Solaris system.


The third mode of operation is used for disk diagnostics. In this
mode, a section of the disk can be filled with a user-specified
pattern and mode sections of the disk can also be read or written.

Note -

The third mode of operation is not currently supported for extended
partitions


When fdisk creates a partition, the space is allocated in the fdisk
partition table, but the allocated disk space is not initialized.
newfs(8) is required to create and write file system metadata to the
new partition, and format(8) is required to write the VTOC or EFI/GPT
metadata.

Menu Options

The menu options for interactive mode given by the fdisk program are:

Create a partition

This option allows the user to create a new partition. The
maximum number of partitions is 4. The program will ask for the
type of the partition (SOLARIS, MS-DOS, UNIX, or other). It will
then ask for the size of the partition as a percentage of the
disk. The user may also enter the letter c at this point, in
which case the program will ask for the starting cylinder number
and size of the partition in cylinders. If a c is not entered,
the program will determine the starting cylinder number where the
partition will fit. In either case, if the partition would
overlap an existing partition or will not fit, a message is
displayed and the program returns to the original menu.


Change Active (Boot from) partition

This option allows the user to specify the partition where the
first-stage bootstrap will look for the second-stage bootstrap,
otherwise known as the active partition.


Delete a partition

This option allows the user to delete a previously created
partition. Note that this will destroy all data in that
partition.


Change between Solaris and Solaris2 Partition IDs

This option allows the user to switch between the current fdisk
operating system partition identifier and the previous one. This
does not affect any data in the disk partition and is provided
for compatibility with older software.


Edit/View extended partitions

This option provides the extended partition menu to the user. Use
the extended partition menu to add and delete logical drives,
change the sysid of the logical drives, and display logical drive
information. To commit the changes made in the extended
partition, you must return to the main menu using the extended
partition submenu option r. There is also an option to display
the list of options that the extended partition submenu supports.
Given below is the list:

a
Add a logical drive.

Use this submenu option to add a logical drive. There are
three pieces of information that are required: The beginning
cylinder, the size (in cylinders or in human readable form -
KB, MB, or GB), and the partition ID. While specifying the
partition ID, there is an option (I) that you can use to
list the supported partitions.


d
Delete a logical drive.

Use this submenu option to delete a logical drive. The only
input required is the number of the logical drive that is to
be deleted.


h
Display the help menu.

This submenu option displays the supported operations in the
extended partition submenu.


i
Change the id of the logical drive.

Use this submenu option to change the system ID of the
existing logical drives. A list of supported system IDs is
displayed when you use the I option when in this submenu.


p
Display the logical drive layout.

Displays the logical drive information to stdout. This
output reflects any changes made during the current run of
the fdisk program. The changes are not committed to the disk
until return to the main menu (using the submenu r) and
choose the option to commit the changes to the disk.


r
Return to the main fdisk menu.

Exit the extended partition submenu and return to the main
menu.


Use the following options to include your modifications to the
partition table at this time or to cancel the session without
modifying the table:

Exit
This option writes the new version of the table created
during this session with fdisk out to the fixed disk, and
exits the program.


Cancel
This option exits without modifying the partition table.

OPTIONS

The following options apply to fdisk:

-A id:act:bhead:bsect:bcyl:ehead:esect:ecyl:rsect:numsect

Add a partition as described by the argument (see the -F option
below for the format). Use of this option will zero out the VTOC
on the Solaris partition if the fdisk table changes.


-b master_boot

Specify the file master_boot as the master boot program. The
default master boot program is /boot/pmbr.


-B

Default to one Solaris partition that uses the whole disk. On an
x86 machine, if the disk is larger than 2 TB (terabytes), the
default size of the Solaris partition will be limited to 2 TB.


-d

Turn on verbose debug mode. This will cause fdisk to print its
state on stderr as it is used. The output from this option should
not be used with -F.


-D id:act:bhead:bsect:bcyl:ehead:esect:ecyl:rsect:numsect

Delete a partition as described by the argument (see the -F
option below for the format). Note that the argument must be an
exact match or the entry will not be deleted! Use of this option
will zero out the VTOC on the Solaris partition if the fdisk
table changes.


-E [slot:active]

Create an EFI partition that uses the entire disk.

By default this partition entry will be placed into the first
slot within the partition table and will not be marked active.
The remaining slots within the table will be zeroed out.

Some broken firmware implementations have issues booting in
CSM/Legacy/BIOS mode from EFI partitions that are not set active.
Others have issues with booting from EFI partitions without UEFI
if the protective partition table entry is in the first slot. To
work around these problems, the -E option takes an optional
argument which can be used to override the defaults described
above.


slot
Specify the MBR slot into which the EFI partition
should be placed. This accepts a value in the range 0
to 3 with the default being 0.


active
Specify whether the EFI partition entry should be
marked active; 0 specifies not active (the default)
and 1 means active.


-F fdisk_file

Use fdisk file fdisk_file to initialize table. Use of this option
will zero out the VTOC on the Solaris partition if the fdisk
table changes.

The fdisk_file contains four specification lines for the primary
partitions followed by specification lines for the logical
drives. You must have four lines for the primary partitions if
there is at least one logical drive. In this case, if the number
of primary partitions to be configured is less than four, the
remaining lines should be filled with zeros.

Each line is composed of entries that are position-dependent, are
separated by whitespace or colons, and have the following format:

id act bhead bsect bcyl ehead esect ecyl rsect numsect

...where the entries have the following values:

id
This is the type of partition and the correct numeric
values may be found in fdisk.h.


act
This is the active partition flag; 0 means not active
and 128 means active. For logical drives, this flag
will always be set to 0 even if specified as 128 by
the user.


bhead
This is the head where the partition starts. If this
is set to 0, fdisk will correctly fill this in from
other information.


bsect
This is the sector where the partition starts. If this
is set to 0, fdisk will correctly fill this in from
other information.


bcyl
This is the cylinder where the partition starts. If
this is set to 0, fdisk will correctly fill this in
from other information.


ehead
This is the head where the partition ends. If this is
set to 0, fdisk will correctly fill this in from other
information.


esect
This is the sector where the partition ends. If this
is set to 0, fdisk will correctly fill this in from
other information.


ecyl
This is the cylinder where the partition ends. If this
is set to 0, fdisk will correctly fill this in from
other information.


rsect
The relative sector from the beginning of the disk
where the partition starts. This must be specified
and can be used by fdisk to fill in other fields. For
logical drives, you must make sure that there are at
least 63 free sectors before the rsect specified for a
logical drive.


numsect
The size in sectors of this disk partition. This must
be specified and can be used by fdisk to fill in other
fields.


-g

Get the label geometry for disk and display on stdout (see the -S
option for the format).


-G

Get the physical geometry for disk and display on stdout (see the
-S option for the format).


-h

Issue verbose message; message will list all options and supply
an explanation for each.


-I

Forgo device checks. This is used to generate a file image of
what would go on a disk without using the device. Note that you
must use -S with this option (see above).


-n

Don't update fdisk table unless explicitly specified by another
option. If no other options are used, -n will only write the
master boot record to the disk. In addition, note that fdisk will
not come up in interactive mode if the -n option is specified.


-o offset

Block offset from start of disk. This option is used for -P, -r,
and -w. Zero is assumed when this option is not used.


-P fill_patt

Fill disk with pattern fill_patt. fill_patt can be decimal or hex
and is used as number for constant long word pattern. If
fill_patt is #, then pattern is block # for each block. Pattern
is put in each block as long words and fills each block (see -o
and -s).


-r

Read from disk and write to stdout. See -o and -s, which specify
the starting point and size of the operation.


-R

Treat disk as read-only. This is for testing purposes.


-s size

Number of blocks to perform operation on (see -o).


-S geom_file

Set the label geometry to the content of the geom_file. The
geom_file contains one specification line. Each line is delimited
by a new-line character (\n). If the first character of a line is
an asterisk (*), the line is treated as a comment. Each line is
composed of entries that are position-dependent, are separated by
white space, and have the following format:

pcyl ncyl acyl bcyl nheads nsectors sectsiz


where the entries have the following values:

pcyl
This is the number of physical cylinders for the
drive.


ncyl
This is the number of usable cylinders for the drive.


acyl
This is the number of alt cylinders for the drive.


bcyl
This is the number of offset cylinders for the drive
(should be zero).


nheads
The number of heads for this drive.


nsectors
The number of sectors per track.


sectsiz
The size in bytes of a sector.


-t

Adjust incorrect slice table entries so that they will not cross
partition table boundaries.


-T

Remove incorrect slice table entries that span partition table
boundaries.


-v

Output the HBA (virtual) geometry dimensions. This option must be
used in conjunction with the -W flag. This option will work for
platforms which support virtual geometry. (x86 only)


-w

Write to disk and read from stdin. See -o and -s, which specify
the starting point and size of the operation.


-W -

Output the disk table to stdout.


-W fdisk_file

Create an fdisk file fdisk_file from disk table. This can be used
with the -F option below.

FILES

/dev/rdsk/c0t0d0p0
Raw device associated with the fixed disk.


/boot/pmbr
Default master boot program.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|Architecture | x86 and SPARC |
+---------------+-----------------+

SEE ALSO

uname(1), attributes(7), fmthard(8), format(8), newfs(8), prtvtoc(8)

DIAGNOSTICS

Most messages will be self-explanatory. The following may appear
immediately after starting the program:

Fdisk: cannot open <device>

This indicates that the device name argument is not valid.


Fdisk: unable to get device parameters for device <device>

This indicates a problem with the configuration of the fixed
disk, or an error in the fixed disk driver.


Fdisk: error reading partition table

This indicates that some error occurred when trying initially to
read the fixed disk. This could be a problem with the fixed disk
controller or driver, or with the configuration of the fixed
disk.


Fdisk: error writing boot record

This indicates that some error occurred when trying to write the
new partition table out to the fixed disk. This could be a
problem with the fixed disk controller, the disk itself, the
driver, or the configuration of the fixed disk.


December 6, 2018 FDISK(8)