FIXPARTS(8) FixParts Manual FIXPARTS(8)NAMEfixparts - MBR partition table repair utility
SYNOPSISfixparts device
DESCRIPTION
FixParts (aka fixparts) is a text-mode menu-driven program for repair‐
ing certain types of problems with Master Boot Record (MBR) partition
tables. The program has three design goals, although a few additional
features are supported, as well:
* It can remove stray GUID Partition Table (GPT) data, which can
be left behind on a disk that was once used as a GPT disk but
then incompletely converted to the more common (as of 2011) MBR
form.
* It can repair mis-sized extended partitions -- either partitions
that extend beyond the physical end of the disk or that overlap
with nearby primary partitions. FixParts is designed in such a
way that this type of repair occurs automatically, so if it's
the only problem with your disk, you can launch the program and
then immediately save the partition table, making no manual
changes, and the program will fix the problem.
* You can change primary partitions into logical partitions or
vice-versa, within constraints imposed by the MBR data struc‐
tures.
Additional features include the ability to change partition type codes
or boot/active flags, to delete partitions, and to recompute CHS val‐
ues. With the possible exception of recomputing CHS values, these sec‐
ondary features are better performed with fdisk, because fixparts'
design means that it's likely to alter partition numbering even when
such changes are not requested.
The fixparts program employs a user interface similar to that of
Linux's fdisk, but fixparts is much more specialized. Most importantly,
you can't create new partitions with fixparts, although you can change
primary/logical assignment.
In the MBR scheme, partitions come in three varieties:
primary
These partitions are defined in the first sector of the hard
disk and are limited in number to four. Some OSes, such as Win‐
dows and FreeBSD, must boot from a primary partition.
extended
Extended partitions are specialized primary partitions. They
serve as holding areas for logical partitions.
logical
A disk can contain an arbitrary number of logical partitions
(fixparts, however, imposes a limit of 124 logical partitions).
All the logical partitions reside inside a single extended par‐
tition, and are defined using a linked-list data structure. This
fact means that every logical partition must be preceded by at
least one sector of unallocated space to hold its defining data
structure (an Extended Boot Record, or EBR).
These distinctions mean that primary and logical partitions cannot be
arbitrarily interspersed. A disk can contain one to three primary par‐
titions, a block of one or more logical partitions, and one to three
more primary partitions (for a total of three primary partitions, not
counting the extended partition). Primary partitions may not be sand‐
wiched between logical partitions, since this would mean placing a pri‐
mary partition within an extended partition (which is just a specific
type of primary partition).
Unlike most disk utilities, fixparts' user interface ignores extended
partitions. Internally, the program discards the information on the
original extended partition and, when you tell it to save its changes,
it generates a new extended partition to contain the then-defined logi‐
cal partitions. This is done because most of the repairs and manipula‐
tions the tool performs require generating a fresh extended partition,
so keeping the original in the user interface would only be a complica‐
tion.
Another unusual feature of fixparts' user interface is that partition
numbers do not necessarily correlate with primary/logical status. In
most utilities, partitions 1-4 correspond to primary partitions,
whereas partitions 5 and up are logical partitions. In fixparts, any
partition number may be assigned primary or logical status, so long as
the rules for layout described earlier are obeyed. When the partition
table is saved, partitions will be assigned appropriately and then
tools such as the Linux kernel and fdisk will give them conventional
numbers.
When it first starts, fixparts performs a scan for GPT data. If the
disk looks like a conventional GPT disk, fixparts refuses to run. If
the disk appears to be a conventional MBR disk but GPT signatures are
present in the GPT primary or secondary header areas, fixparts offers
to delete this extraneous data. If you tell it to do so, the program
immediately wipes the GPT header or headers. (If only one header was
found, only that one header will be erased, to minimize the risk of
damaging a boot loader or other data that might have overwritten just
one of the GPT headers.)
With the exception of optionally erasing leftover GPT data when it
first starts, fixparts keeps all changes in memory until the user
writes changes with the w command. Thus, you can adjust your partitions
in the user interface and abort those changes by typing q to quit with‐
out saving changes.
OPTIONS
The fixparts utility supports no command-line options, except for spec‐
ification of the target device.
Most interactions with fixparts occur with its interactive text-mode
menu. Specific functions are:
a Toggle the active/boot flag. This flag is required by some boot
loaders and OSes.
c Recompute the cylinder/head/sector (CHS) values for all parti‐
tions. CHS addressing mode is largely obsolete, but some OSes
and utilities complain if they don't like the CHS values. Note
that fixparts' CHS values are likely to be incorrect on disks
smaller than about 8 GiB except on Linux.
l Change a partition's status to logical. This option will only
work if the current partition layout supports such a change.
Note that if changing a partition's status in this way is not
currently possible, making some other change may make it possi‐
ble. For instance, omitting a partition that precedes the target
partition may enable converting a partition to logical form if
there had been no free sectors between the two partitions.
o Omit a partition. Once omitted, the partition will still appear
in the fixparts partition list, but it will be flagged as omit‐
ted. You can subsequently convert it to primary or logical form
with the r or l commands, respectively. When you save your
changes with w, though, the partition will be lost.
p Display basic partition summary data. This includes partition's
number, the boot/active flag's status, starting and ending sec‐
tor numbers, primary/logical/omitted status, whether or not the
partition may be converted to logical form, and the partition's
MBR types code.
q Quit from the program without saving your changes. Use this
option if you just wanted to view information or if you make a
mistake and want to back out of all your changes.
r Change a partition's status to primary. This option will only
work if the current partition layout supports such a change.
Note that every partition can theoretically become a primary
partition, although in some configurations, making this change
will require omitting some partitions. If fixparts refuses to
allow changing a partition to primary, you may need to convert
other partitions to logical form or omit them entirely.
s Sort partition entries. This option orders partitions in the
display to match their on-disk positions, which can make under‐
standing the disk layout easier in some cases. This option has
no effect on the ultimate ordering of logical partitions, which
are sorted before being saved. The order of primary partitions
in the final saved partition table may be affected by this
option. In both cases, as already noted, the partition numbers
displayed by fixparts may not be the same as those used by the
kernel or displayed by other partitioning tools.
t Change a partition's type code. You enter the type code using a
one-byte hexadecimal number.
w Write data. Use this command to save your changes and exit from
the program.
? Print the menu. Type this command (or any other unrecognized
command) to see a summary of available options.
BUGS
Known bugs and limitations include:
* The program compiles correctly only on Linux, FreeBSD, Mac OS X,
and Windows. Linux versions for x86-64 (64-bit), x86 (32-bit),
and PowerPC (32-bit) have been tested, with the x86-64 version
having seen the most testing. Under FreeBSD, 32-bit (x86) and
64-bit (x86-64) versions have been tested. Only 32-bit versions
for Mac OS X and Windows have been tested.
* The FreeBSD version of the program can't write changes to the
partition table to a disk when existing partitions on that disk
are mounted. (The same problem exists with many other FreeBSD
utilities, such as gpt, fdisk, and dd.) This limitation can be
overcome by typing sysctl kern.geom.debugflags=16 at a shell
prompt.
* The program can load only up to 128 partitions (4 primary parti‐
tions and 124 logical partitions). This limit can be raised by
changing the #define MAX_MBR_PARTS line in the basicmbr.h source
code file and recompiling.
* The program can read partitions only if the disk has correct LBA
partition descriptors. These descriptors should be present on
any disk over 8 GiB in size or on smaller disks partitioned with
any but very ancient software.
* The program makes no effort to preserve partition numbers. This
can have consequences for boot loaders and for mounting filesys‐
tems via /etc/fstab. It may be necessary to edit configuration
files or even to re-install your boot loader.
*
The program may change the order of partitions in the partition
table.
AUTHORS
Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
Contributors:
* Yves Blusseau (1otnwmz02@sneakemail.com)
* David Hubbard (david.c.hubbard@gmail.com)
* Justin Maggard (justin.maggard@netgear.com)
* Dwight Schauer (dschauer@gmail.com)
* Florian Zumbiehl (florz@florz.de)
SEE ALSO
cfdisk (8), cgdisk (8), fdisk (8), mkfs (8), parted (8), sfdisk (8)
gdisk (8) sgdisk (8)
http://en.wikipedia.org/wiki/Master_boot_record
http://www.rodsbooks.com/fixparts/
AVAILABILITY
The fixparts command is part of the GPT fdisk package and is available
from Rod Smith.
Roderick W. Smith 1.0.3 FIXPARTS(8)
