GPT fdisk (aka gdisk) and FixParts | |
by Roderick W. Smith, rodsmith@rodsbooks.com | |
******************************** IMPORTANT ******************************** | |
Most versions of Windows cannot boot from a GPT disk on BIOS-based | |
computers, and most varieties prior to Vista cannot read GPT disks. GPT | |
fdisk is a partition editor for GPT disks, and it will *AUTOMATICALLY | |
CONVERT* MBR disks to GPT form. Therefore, you should **NOT** use GPT fdisk | |
on a Windows system unless you fully understand what you're doing! If you | |
accidentally use GPT fdisk on your boot disk, or perhaps even on a data | |
disk, you may find recovery to be very difficult! This caveat does not | |
apply to FixParts, though; that tool works only on MBR disks. | |
*************************************************************************** | |
Read the main README file for general information on the program, and read | |
the gdisk.html or fixparts.html documents (the Linux man pages converted to | |
HTML format) for detailed use information. My GPT fdisk Web page, | |
http://www.rodsbooks.com/gdisk/, provides a more tutorial introduction to | |
the software. I originally wrote GPT fdisk on Linux, and some Linux- and | |
Unix-centric language remains in the documentation. | |
Windows Use Notes | |
----------------- | |
The Windows version of GPT fdisk was added with version 0.6.2 of the | |
package. The Windows binary package includes the gdisk.exe interactive | |
text-mode program file but no equivalent to the sgdisk program that's | |
available with Linux, FreeBSD, and OS X builds. In theory, an sgdisk.exe | |
for Windows could be built if the popt library were installed. I've not | |
attempted to do this myself, though. If you care to try, check | |
http://gnuwin32.sourceforge.net/packages/popt.htm for information on popt | |
for Windows. | |
The FixParts program (fixparts.txt) is new with GPT fdisk 0.7.0. As | |
described in the main README file, this program fixes certain partition | |
table problems that can be created by buggy partitioning software. Windows | |
seems to be unfazed by most such problems, but I've not done an extensive | |
survey of Windows partitioning tools on this score. | |
To install the programs, copy the gdisk.exe and fixparts.exe program files | |
to any directory on your path, such as C:\Windows. Alternatively, you can | |
change to the program's directory or type its complete path whenever you | |
use it. | |
To use the programs, first launch a Command Prompt as the Administrator. To | |
do this, locate the Command Prompt program icon, right-click it, and select | |
"Run as Administrator." If you use a non-Administrator Command Prompt, you | |
won't be able to edit hard disk partition tables, although you will be able | |
to edit raw disk image files. | |
The program requires a hard disk identifier as an option. You can specify | |
this in either of two forms. The first way is as a number followed by a | |
colon, as in: | |
gdisk 0: | |
Disks are numbered starting from 0, so the preceding command launches gdisk | |
on the first disk. The second way to specify a disk device is via a | |
harder-to-remember name: | |
gdisk \\.\physicaldrive0 | |
This command is equivalent to the earlier one -- it edits the partition | |
table on the first physical disk. Change the number at the end of the | |
device name to change the disk edited. | |
If you pass the "-l" option to gdisk.exe in addition to the disk | |
identifier, the program displays the current partition table information | |
and then exits. This use entails no risk to MBR disks, since the program | |
never writes data back to the disk when used in this way. | |
As noted above, editing the first disk with GPT fdisk is usually a Bad | |
Idea. An exception would be if your system uses an Extensible Firmware | |
Interface (EFI) and already boots from a GPT disk. It's safer to edit | |
non-boot disks, which usually have numbers of 1 and above, but only if you | |
run a version of Windows with GPT support. For more information on Windows' | |
support of GPT, see Microsoft's Web page on the topic: | |
http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx | |
The GUIDs generated by gdisk to uniquely identify disks and partitions | |
aren't "proper" GUIDs; they're purely random numbers. In practice, this has | |
caused me no problems; however, it's conceivable that some disk utility | |
will complain. The Unix versions of GPT fdisk generate proper GUIDs, as of | |
version 0.6.3. Note that this limitation applies ONLY to the unique GUIDs | |
for disks and partitions, not to the GUIDs used to identify partition type | |
codes; those are standardized and are handled correctly by all versions of | |
GPT fdisk. | |
The Windows binaries I've compiled do not support Unicode UTF-16LE GPT | |
partition names. This feature was added to version 0.7.1 of the software | |
for Linux, FreeBSD, and OS X, and with changes to some #ifndef lines in the | |
source files, it can be compiled for Windows; however, it seems to do | |
little good in Windows because of Command Prompt window and/or ICU library | |
limitations. Thus, I've omitted this support in the interests of | |
simplifying the binary distribution, since including it would mean | |
distributing the ICU libraries. | |
Source Code and Compilation Issues | |
---------------------------------- | |
I have successfully compiled GPT fdisk using three different Windows | |
compilers: | |
- MinGW (http://www.mingw.org), and in particular its Linux-hosted | |
cross-compiler -- Under Fedora Linux, the Makefile.mingw file enables | |
compilation of the software via MinGW. (Type "make -f Makefile.mingw" to | |
compile the software.) If you try to compile using another compiler or | |
even using MinGW under Windows or another Linux variety, you may need to | |
adjust the Makefile.mingw options. | |
- Microsoft Visual C++ 2008 Express | |
(http://www.microsoft.com/express/Windows/) -- This compiler requires a | |
third-party stdint.h file (I used the one from | |
http://msinttypes.googlecode.com/svn/trunk/stdint.h), but it otherwise | |
works fine. A project is easily created by adding all the *.h files and | |
all the *.cc files except diskio-unix.cc, sgdisk.cc, and whichever | |
program file you intend to NOT build (gdisk.cc or fixparts.cc). | |
- Microsoft Visual C++ 2010 Express -- This compiler works much like the | |
2008 version, although I didn't need to add a third-party stdint.h file. | |
The MinGW compiler produces much larger executables than do the MS | |
compilers. The resulting binaries seem to work equally well, but my testing | |
has been minimal. | |
I've also attempted to compile the code with OpenWatcom 1.8, but this | |
attempt failed, mostly because the compiler can't yet handle iostream | |
output on standard C++ strings. OpenWatcom also seems to have incorrectly | |
set the value of UINT32_MAX as if uint32_t values were 64-bit integers. | |
This alone won't cause the compile to fail, but it would create bugs. | |
If you modify GPT fdisk to get it to compile under another compiler, I | |
welcome submission of patches. |