Introduction to GDisk
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Introduction to GDisk


Article ID: 178424


Updated On:


Deployment Solution


 You want to know what Ghost's GDisk utility can do and when it can be used in place of the Windows FDisk utility.


GDisk is a DOS command-line utility, GDisk.exe, that includes all the features of FDisk and additional features. Everything you can do with FDisk you can do with GDisk. Partitions that are created with GDisk are indistinguishable from those that are created with FDisk.

Because GDisk runs only in DOS, you cannot access GDisk from within Windows. Instead, copy GDisk.exe to a floppy disk, start the computer from a bootable floppy disk, and run GDisk from the floppy disk. GDisk is located on the Ghost installation CD and in the Ghost installation folder on your hard disk.

GDisk has six main modes of operation, the first four of which correspond to the menu options in FDisk's main menu:

Creating partitions - Primary DOS partitions, Extended DOS partitions, Logical DOS drives.

Deleting partitions of any type, including Non-DOS partitions.

Listing current partition information.

Activating a partition (nominating it as the bootable partition).

Making existing partitions invisible and visible again.

Reinitializing the Master Boot Record.

Batch Mode - a mode that enables multiple commands in the same GDisk session.

Advantages over FDisk

GDisk provides some capabilities that FDisk does not -- such as on-the-fly formatting -- and provides a safer alternative in situations in which known problems with FDisk can cause data loss and hardware damage.


GDisk is command-line driven and much quicker than FDisk. It allows you to define standard configurations in a batch file and apply them to multiple computers.

Disk space

GDisk uses disk space better. It is more aggressive in finding free space on the disk for new partitions. In virtually every case it will find space that is ignored by FDisk (this space can vary between 0.5 MB and 16 MB).

GDisk reduces slack space (disk wastage). GDisk is more aggressive than the FORMAT utility provided with Windows 95 in attempting to keep cluster sizes small. For some partition sizes, GDisk is able to format partitions with cluster sizes that are half the size that FORMAT would select, resulting in an effective 10-35% increase in drive capacity.

Partition management

GDisk allows you to hide partitions, so you can have more than one Primary DOS partition with different versions of DOS or Windows in each partition. Normally, it is not possible to have more than one DOS or Windows installation on the same computer. The ability to hide partitions allows the computer to boot into any selected bootable partition, ignoring other installations of the same operating system in other partitions.

Avoid known FDisk problems

The FDisk supplied with Windows 95 has a problem that can create overlapping partitions that will almost certainly lead to corruption of existing partitions. The same problem can also result in partitions that extend past the end of the disk, which can cause permanent damage to the drive when the partition is formatted. This is the one situation in which GDisk does not imitate the exact behavior of FDisk, even with the compatibility switch turned on.

The FDisk supplied with Windows 95 has a problem in which it is not possible to delete newly created partitions if the provisionally assigned drive letter to the new drive matches a drive letter currently assigned to a CD-ROM device. GDisk allows the partitions to be deleted even if the new drive letter is currently assigned.


GDisk is useful as a diagnostic tool. It performs extensive integrity verification checks on the partition tables before performing any operations on the drive.

GDisk can display the partition information in a raw cylinder/head/sector format. This may be of use to technicians investigating problems with a computer's partition table.

DoD specifications

GDisk.exe conforms to most current US Department of Defense (DoD) specifications.



Norton Ghost 2002, 2003, and Symantec Ghost 7.5 include two versions of GDisk: GDisk.exe and GDisk32.exe. The newest version of GDisk, GDisk32.exe, is a 32 bit program that can be run from within a DOS virtual machine. Use this version when you want to run GDisk from within Windows. This version uses the same command-line switches as GDisk.exe.

GDisk32.exe conforms to most current US Department of Defense (DoD) specifications.

Use GDisk32.exe for:

Unhiding a partition that the Windows NT or Windows 2000 Disk Manager cannot see.

Activating a diagnostic or recovery partition.

Adding or removing an operating system from the Windows NT or Windows 2000 Boot Menu. GDisk32.exe includes a new switch, -BOOTINI, for adding or removing entries from the Windows NT or Windows 2000 file Boot.ini. That is, when you use the -BOOTINI switch to add or remove entries from the Windows Boot.ini file, you change which operating systems are available on the Windows Boot Menu. For instance, if you installed Windows 98 to the computer and then Windows 2000, the Windows 2000 boot menu might not display Windows 98. Use -BOOTINI to add the Windows 98 partition to the file Boot.ini.


Additional Information

For more information on switches, see KB: 178425: Switches used in GDisk