GPT fdisk Tutorial
Last Web page update: 1/9/2013, referencing GPT fdisk version 0.8.6
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GPT fdisk (consisting of the gdisk, cgdisk,
sgdisk, and fixparts programs) is a set of text-mode
partitioning tools for Linux, FreeBSD, Mac OS X, and Windows. The
gdisk, cgdisk, and sgdisk programs work on
Globally Unique Identifier (GUID) Partition Table (GPT) disks, rather than
on the more common (through 2011) Master Boot Record (MBR) partition
tables. The fixparts program repairs certain types of damage to
MBR disks and enables changing partition types from primary to logical and
vice-versa. You can learn more about fixparts on its dedicated Web page. If
gdisk, cgdisk, and sgdisk sound interesting to
you, then read on (or skip straight to the "Obtaining GPT fdisk" link if
you don't need the GPT pep talk). If you don't know what a GPT is, be sure
to read the first section!
FreeBSD users: The FreeBSD version of GPT fdisk can't
normally save changes to your partition table if any partition from the
disk is mounted. If you want to modify your FreeBSD boot disk, the safest
way to do so is from an emergency system or from a dual boot to another OS.
Alternatively, you can type sysctl kern.geom.debugflags=16
at a shell prompt to enable FreeBSD to write to active disks. This
limitation is shared by at least some other FreeBSD partitioning tools,
such as gpt and FreeBSD's fdisk. This limitation does
not exist in the Linux, Mac OS X, or Windows versions of the
Windows users: Windows cannot boot from a GPT disk
unless the computer uses Unified Extensible Firmware Interface (UEFI)
firmware, and versions prior to Vista may not be able to read GPT disks at
all. Since GPT fdisk automatically turns MBR disks into GPT disks, you
should use GPT fdisk only if you're positive your system can handle them.
GPT FAQ for more information on Windows GPT support. If you have a
BIOS-based computer and desperately need to boot from a GPT disk, consult
my BIOS to UEFI
Transformation Web page.
- What's a GPT?—A summary of basics about
- Working Around MBR's Limitations—A
couple of ways to eek a bit more life out of MBR
- Legacy BIOS Issues with GPT—Information
on obscure issues related to BIOS/GPT coexistence
- Why Use GPT fdisk?—Advice on when to use
GPT fdisk vs. its alternatives
- A gdisk Walkthrough—A
demonstration of how to use GPT fdisk's interactive gdisk
tool, which is a powerful tool for experts.
- An cgdisk
Walkthrough—A demonstration of how to use GPT fdisk's
command-line cgdisk tool, which is easier to use for
- An sgdisk
Walkthrough—A demonstration of how to use GPT fdisk's
command-line gdisk tool, which is intended for use in scripts
or by experts to do quick tasks.
- Partitioning Advice—General suggestions on
how to lay out your GPT partitions
- Converting to or from GPT—If you want
to convert an existing MBR or BSD disklabel disk to use GPT, or convert
GPT to MBR, read this!
- Wiping Out GPT Data—If you need to
re-partition a GPT disk using MBR, read this first!
- Booting from GPT—Advice on booting Linux,
FreeBSD, Windows, and Mac OS X from GPT disks
- Hybrid MBRs—Information on this
non-standard, ugly, flaky, dangerous, but occasionally useful GPT
- Repairing GPT Disks—When a GPT disk's
data structures are damaged, GPT fdisk can help you recover your data.
- Obtaining GPT fdisk—How to get the
- Revisions—GPT fdisk's revision history.
The Linux man pages for all of the GPT fdisk programs are available
Using GPT fdisk on Any Computer
At least three Linux emergency systems ship with GPT fdisk. You can
create a bootable CD-R, boot it, and use GPT fdisk (and many other useful
Linux utilities) even on systems on which GPT fdisk doesn't compile. These
tools are also very useful for Linux, FreeBSD, Mac OS X, Windows, and other
systems when things go wrong or when performing certain types of offline
The emergency disks I know of that include GPT fdisk are:
Note that GPT fdisk is a Linux text-mode tool, so you'll need to know
at least a minimal amount about using a Linux text-mode shell. Many basic
introductions are available on the Web. One I found pretty quickly and that
seems to provide a fairly gentle introduction is located here.
You'll need to learn only enough to do very basic tasks; I've got a GPT fdisk walkthrough that describes GPT fdisk
itself. Depending on your rescue CD and how you launched it, you may find
yourself at a text-mode shell when you first boot, or you may need to
locate an item called "Terminal," "Shell," "xterm," or something similar to
start your text-mode shell.
- GPT fdisk's
Sourceforge page—The preferred download method for source
code and non-Linux binaries. (For Linux binaries, see the "Obtaining GPT fdisk" page.)
- Intel's EFI page
includes links to various EFI resources, including the EFI
specifications, which include the official GPT 1.x specification. (In
version 1.10, section 188.8.131.52 describes GPT.) Note, however, that most
PCs with EFI support use the newer UEFI 2.x (see next bullet point).
- The UEFI 2.x specifications and
tools detail UEFI 2.x, as implemented on some modern PC
motherboards. The GPT structure is described in Section 5 (and
especially Section 5.3) of the UEFI 2.3 specification. Note that UEFI
2.x uses the same GPT format (1.0) as described in version 1.x of the
EFI specification, although the description has been clarified or
expanded in a few areas. The GPT version number is unrelated to the
EFI/UEFI version number.
the Most of Large Drives with GPT and Linux"—An informational
piece on GPT I wrote for IBM developerWorks.
informational piece on GPT, on the SystemRescueCd Web page.
Wikipedia entry on GPT—This has lots of useful technical
information, including the most complete set of GUID partition codes
I've seen in one place. (I implemented them all in gdisk, but
there may be more by the time you read this.)
- The Wikipedia
entry on MBR—This has lots of useful technical information on
MBR, should you want to compare it to the GPT information.
to Partition Tables—Another page with useful MBR information.
- Apple's Technical
Note TN2166—A document that provides technical details on GPT.
- Microsoft's GPT
FAQ—Go here to learn Windows-specific GPT information.
- Microsoft's Recommended
UEFI-Based Disk-Partition Configurations page provides details on
how to partition a UEFI-based computer on which you want to install
- A piece on
Anandtech concerning the transition to 4096-byte sectors in hard
of my IBM developerWorks articles, this time on using disks with
4096-byte sectors in Linux.
- A page on repairing
damage to GPT done by MacDrive under Windows. This page includes a
simple Python utility to repair the damage, but of you can do the same
thing with GPT fdisk.
- A Web page
I've written on recovering MBR disks that GNU Parted, GParted, and
other libparted-based tools can't handle because of an improper
extended partition definition.
- Google's Chromium project Web page includes a
page on disk formats, including information on how ChromeOS uses
GPT disks. (Note: Version 0.6.14 of GPT fdisk added ChromeOS GUIDs.)
- My Web page on rEFInd, a
boot loader project derived from the earlier rEFIt, covers this boot
loader for EFI systems.
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