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283 lines
10 KiB
.\" Copyright 2011-2018 Roderick W. Smith (rodsmith@rodsbooks.com)
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.\" May be distributed under the GNU General Public License
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.TH "FIXPARTS" "8" "1.0.4" "Roderick W. Smith" "FixParts Manual"
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.SH "NAME"
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fixparts \- MBR partition table repair utility
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.SH "SYNOPSIS"
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.BI "fixparts "
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.I device
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.SH "DESCRIPTION"
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FixParts (aka \fBfixparts\fR) is a text\-mode menu\-driven program for
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repairing certain types of problems with Master Boot Record (MBR) partition
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tables. The program has three design goals, although a few additional
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features are supported, as well:
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.TP
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.B *
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It can remove stray GUID Partition Table (GPT) data, which can be left
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behind on a disk that was once used as a GPT disk but then incompletely
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converted to the more common (as of 2011) MBR form.
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.TP
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.B *
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It can repair mis-sized extended partitions \-\- either partitions that
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extend beyond the physical end of the disk or that overlap with nearby
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primary partitions. FixParts is designed in such a way that this type of
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repair occurs automatically, so if it's the only problem with your disk,
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you can launch the program and then immediately save the partition table,
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making no manual changes, and the program will fix the problem.
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.TP
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.B *
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You can change primary partitions into logical partitions or vice\-versa,
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within constraints imposed by the MBR data structures.
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.PP
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Additional features include the ability to change partition type codes or
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boot/active flags, to delete partitions, and to recompute CHS values. With
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the possible exception of recomputing CHS values, these secondary features
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are better performed with \fBfdisk\fR, because \fBfixparts\fR' design means
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that it's likely to alter partition numbering even when such changes are
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not requested.
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The \fBfixparts\fR program employs a user interface similar to that of
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Linux's \fBfdisk\fR, but \fBfixparts\fR is much more specialized. Most
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importantly, you can't create new partitions with \fBfixparts\fR, although
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you can change primary/logical assignment.
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In the MBR scheme, partitions come in three varieties:
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.TP
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.B primary
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These partitions are defined in the first sector of the hard disk and
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are limited in number to four. Some OSes, such as Windows and FreeBSD, must
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boot from a primary partition.
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.TP
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.B extended
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Extended partitions are specialized primary partitions. They serve as
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holding areas for logical partitions.
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.TP
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.B logical
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A disk can contain an arbitrary number of logical partitions
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(\fBfixparts\fR, however, imposes a limit of 124 logical partitions). All
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the logical partitions reside inside a single extended partition, and are
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defined using a linked-list data structure. This fact means that every
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logical partition must be preceded by at least one sector of unallocated space
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to hold its defining data structure (an Extended Boot Record, or EBR).
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.PP
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These distinctions mean that primary and logical partitions cannot be
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arbitrarily interspersed. A disk can contain one to three primary
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partitions, a block of one or more logical partitions, and one to three
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more primary partitions (for a total of three primary partitions, not
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counting the extended partition). Primary partitions may not be sandwiched
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between logical partitions, since this would mean placing a primary
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partition within an extended partition (which is just a specific type of
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primary partition).
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Unlike most disk utilities, \fBfixparts\fR' user interface ignores extended
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partitions. Internally, the program discards the information on the
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original extended partition and, when you tell it to save its changes, it
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generates a new extended partition to contain the then-defined logical
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partitions. This is done because most of the repairs and manipulations the
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tool performs require generating a fresh extended partition, so keeping the
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original in the user interface would only be a complication.
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Another unusual feature of \fBfixparts\fR' user interface is that partition
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numbers do not necessarily correlate with primary/logical status. In most
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utilities, partitions 1\-4 correspond to primary partitions, whereas
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partitions 5 and up are logical partitions. In \fBfixparts\fR, any partition
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number may be assigned primary or logical status, so long as the rules for
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layout described earlier are obeyed. When the partition table is saved,
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partitions will be assigned appropriately and then tools such as the Linux
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kernel and \fBfdisk\fR will give them conventional numbers.
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When it first starts, \fBfixparts\fR performs a scan for GPT data. If the
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disk looks like a conventional GPT disk, \fBfixparts\fR refuses to run. If
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the disk appears to be a conventional MBR disk but GPT signatures are
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present in the GPT primary or secondary header areas, \fBfixparts\fR
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offers to delete this extraneous data. If you tell it to do so, the program
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immediately wipes the GPT header or headers. (If only one header was found,
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only that one header will be erased, to minimize the risk of damaging a
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boot loader or other data that might have overwritten just one of the GPT
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headers.)
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With the exception of optionally erasing leftover GPT data when it first
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starts, \fBfixparts\fR keeps all changes in memory until the user writes
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changes with the \fBw\fR command. Thus, you can adjust your partitions in
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the user interface and abort those changes by typing \fBq\fR to quit
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without saving changes.
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.SH "OPTIONS"
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The \fBfixparts\fR utility supports no command\-line options, except for
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specification of the target device.
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Most interactions with \fBfixparts\fR occur with its interactive text\-mode
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menu. Specific functions are:
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.TP
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.B a
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Toggle the active/boot flag. This flag is required by some boot loaders and
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OSes.
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.TP
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.B c
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Recompute the cylinder/head/sector (CHS) values for all partitions. CHS
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addressing mode is largely obsolete, but some OSes and utilities complain
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if they don't like the CHS values. Note that \fBfixparts\fR' CHS values are
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likely to be incorrect on disks smaller than about 8 GiB except on Linux.
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.TP
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.B l
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Change a partition's status to logical. This option will only work if the
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current partition layout supports such a change. Note that if changing a
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partition's status in this way is not currently possible, making some other
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change may make it possible. For instance, omitting a partition that
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precedes the target partition may enable converting a partition to logical
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form if there had been no free sectors between the two partitions.
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.TP
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.B o
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Omit a partition. Once omitted, the partition will still appear in the
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\fBfixparts\fR partition list, but it will be flagged as omitted. You can
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subsequently convert it to primary or logical form with the \fBr\fR or
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\fBl\fR commands, respectively. When you save your changes with \fBw\fR,
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though, the partition will be lost.
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.TP
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.B p
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Display basic partition summary data. This includes partition's number, the
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boot/active flag's status, starting and ending sector numbers,
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primary/logical/omitted status, whether or not the partition may be
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converted to logical form, and the partition's MBR types code.
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.TP
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.B q
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Quit from the program \fIwithout saving your changes\fR.
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Use this option if you just wanted to view information or if you make a
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mistake and want to back out of all your changes.
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.TP
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.B r
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Change a partition's status to primary. This option will only work if the
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current partition layout supports such a change. Note that every partition
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can theoretically become a primary partition, although in some
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configurations, making this change will require omitting some partitions.
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If \fBfixparts\fR refuses to allow changing a partition to primary, you may
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need to convert other partitions to logical form or omit them entirely.
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.TP
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.B s
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Sort partition entries. This option orders partitions in the display to
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match their on-disk positions, which can make understanding the disk layout
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easier in some cases. This option has no effect on the ultimate ordering of
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logical partitions, which are sorted before being saved. The order of
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primary partitions in the final saved partition table may be affected by
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this option. In both cases, as already noted, the partition numbers
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displayed by \fBfixparts\fR may not be the same as those used by the kernel
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or displayed by other partitioning tools.
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.TP
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.B t
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Change a partition's type code. You enter the type code using a one\-byte
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hexadecimal number.
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.TP
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.B w
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Write data. Use this command to save your changes and exit from the program.
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.TP
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.B ?
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Print the menu. Type this command (or any other unrecognized command) to
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see a summary of available options.
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.PP
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.SH "BUGS"
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Known bugs and limitations include:
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.TP
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.B *
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The program compiles correctly only on Linux, FreeBSD, Mac OS X, and Windows.
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Linux versions for x86\-64 (64\-bit), x86 (32\-bit), and PowerPC (32\-bit) have been
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tested, with the x86\-64 version having seen the most testing. Under FreeBSD,
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32\-bit (x86) and 64\-bit (x86\-64) versions have been tested. Only 32\-bit
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versions for Mac OS X and Windows have been tested.
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.TP
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.B *
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The FreeBSD version of the program can't write changes to the partition
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table to a disk when existing partitions on that disk are mounted. (The
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same problem exists with many other FreeBSD utilities, such as
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\fBgpt\fR, \fBfdisk\fR, and \fBdd\fR.) This limitation can be overcome
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by typing \fBsysctl kern.geom.debugflags=16\fR at a shell prompt.
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.TP
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.B *
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The program can load only up to 128 partitions (4 primary partitions and
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124 logical partitions). This limit can be raised by changing the
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\fI#define MAX_MBR_PARTS\fR line in the \fIbasicmbr.h\fR source code file
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and recompiling.
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.TP
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.B *
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The program can read partitions only if the disk has correct LBA partition
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descriptors. These descriptors should be present on any disk over 8 GiB in
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size or on smaller disks partitioned with any but very ancient software.
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.TP
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.B *
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The program makes no effort to preserve partition numbers. This can have
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consequences for boot loaders and for mounting filesystems via
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\fB/etc/fstab\fR. It may be necessary to edit configuration files or even
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to re-install your boot loader.
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.TP
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.B *
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The program may change the order of partitions in the partition table.
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.PP
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.SH "AUTHORS"
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Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
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Contributors:
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* Yves Blusseau (1otnwmz02@sneakemail.com)
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* David Hubbard (david.c.hubbard@gmail.com)
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* Justin Maggard (justin.maggard@netgear.com)
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* Dwight Schauer (dschauer@gmail.com)
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* Florian Zumbiehl (florz@florz.de)
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.SH "SEE ALSO"
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.BR cfdisk (8),
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.BR cgdisk (8),
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.BR fdisk (8),
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.BR mkfs (8),
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.BR parted (8),
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.BR sfdisk (8),
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.BR gdisk (8),
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.BR sgdisk (8).
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\fIhttp://en.wikipedia.org/wiki/Master_boot_record\fR
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\fIhttp://www.rodsbooks.com/fixparts/\fR
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.SH "AVAILABILITY"
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The \fBfixparts\fR command is part of the \fIGPT fdisk\fR package and is
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available from Rod Smith.
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