GPT fdisk (aka gdisk)
by Roderick W. Smith, rodsmith@rodsbooks.com

Introduction
------------

This software is intended as a (somewhat) fdisk-workalike program for
GPT-partitioned disks. Although libparted and programs that use it (GNU
Parted, gparted, etc.) provide the ability to handle GPT disks, they have
certain limitations that gdisk overcomes. Specific advantages of gdisk and
sgdisk include:

* The ability to convert MBR-partitioned disks in-place to GPT format,
  without losing data

* The ability to convert BSD disklabels in-place to create GPT
  partitions, without losing data

* The ability to specify sector-exact partition sizes

* More flexible specification of filesystem type code GUIDs, which
  GNU Parted tends to corrupt (particularly for FAT partitions)

* Clear identification of the number of unallocated sectors on a
  disk

* A user interface that's familiar to long-time users of Linux
  fdisk (gdisk only)

* The MBR boot loader code is left alone (GNU Parted tends to
  wipe it out with every change)

* The ability to create a hybrid MBR, which permits GPT-unaware
  OSes to access up to three GPT partitions on the disk

Of course, GPT fdisk isn't without its limitations. Most notably, it lacks
the filesystem awareness and filesystem-related features of GNU Parted. You
can't resize a partition's filesystem or create a partition with a
filesystem already in place with gdisk, for instance. There's no GUI
version of gdisk.

The GPT fdisk package provides two program files: the interactive text-mode
gdisk and the command-line-driven sgdisk. The former is intended for use in
manually partitioning disks or changing partitioning details; the latter is
intended for use in scripts to help automate tasks such as disk cloning or
preparing multiple disks for Linux installation.

Installing
----------

To compile GPT fdisk, you must have appropriate development tools
installed, most notably the GNU Compiler Collection (GCC) and its g++
compiler for C++. The sgdisk program also requires the popt library and its
development files (headers). Most Linux distributions install popt by
default, but you may need to install a package called popt-dev, popt-devel,
or something similar to obtain the header files. Mac OS users can find a
version of popt for Mac OS from http://popt.darwinports.com; however,
you'll first need to install DarwinPorts (instructions exist on the
preceding page). Alternatively, you can compile gdisk alone, without
sgdisk; gdisk doesn't require popt.

When all the necessary development tools and libraries are installed, you
can uncompress the package and type "make" at the command prompt in the
resulting directory. The result should be program files called gdisk and
sgdisk. Typing "make gdisk" or "make sgdisk" will compile only the requested
programs. You can use these programs in place or copy the files to a
suitable directory, such as /usr/local/sbin. You can copy the man pages
(gdisk.8 and sgdisk.8) to /usr/local/man/man8 to make them available.

Caveats
-------

THIS SOFTWARE IS BETA SOFTWARE! IF IT WIPES OUT YOUR HARD DISK OR EATS YOUR
CAT, DON'T BLAME ME! To date, I've tested the software on several USB flash
drives, a handful of PATA and SATA hard disks, and several virtual disks in
a QEMU environment. I believe all data-corruption bugs to be squashed, but
I know full well that the odds of my missing something are high. This is
particularly true for large drives; my only direct testing with such disks
is with virtual QEMU disks. I've received user reports of success with
RAID arrays over 2TiB in size, though.

My main development platform is a system running the 64-bit version of
Ubuntu 8.04. I've also tested on 64-bit OpenSuSE, 32-bit Fedora 10, 32-bit
Fedora 11, 32-bit Ubuntu 6.10, 64-bit Ubunut 9.10, 64-bit Gentoo, 32-bit
PowerPC Debian Linux, 32-bit Intel-based Mac OS X 10.5 and 10.6, and 64-bit
FreeBSD 7.1. Problems relating to 64-bit integers on the 32-bit Linux have
been common during development and may crop up in the future. The Mac OS X,
FreeBSD, and big-endian (PowerPC) support are new.

Redistribution
--------------

This program is licensed under terms of the GNU GPL (see the file COPYING).

Acknowledgements
----------------

This code is mostly my own; however, I've used three functions from two
other GPLed programs:

- The code used to generate CRCs is taken from the efone program by
  Krzysztof Dabrowski and ElysiuM deeZine. (See the crc32.h and
  crc32.cc source code files.)

- A function to find the disk size is taken from Linux fdisk by
  A. V. Le Blanc.

Additional code contributors include:

- Yves Blusseau (1otnwmz02@sneakemail.com)

- David Hubbard (david.c.hubbard@gmail.com)