Operations of FDISK: The Basics of FDISK

Operations of FDISK:

The Basics of FDISK

Collected and Written by Martin Coleman © 2001,2002.

Dedicated to Kat

"FDISK: (Pronounced eff-disk) External DOS utility that is used to configure the fixed disk. Allows you to create, delete, and split different partitions of the hard drive."

Introduction:

Welcome to the world of FDISK. FDISK stands for Fixed Disk Editor, which means it edits the Fixed Disk (hard drive, floppy disks are removable data and are NOT fixed). FDISK is a tool that allows you to change the partitioning of your hard disks. For example, you can make partitions for DOS, Linux, FreeBSD, Windows 95, Windows NT, BeOS and many other types of operating systems.

FDISK is used for everything from creating additional "hard drives" for use with your computer to setting up your computer for multiple operating systems (see: Multi-booting).

Using FDISK you can do the following things:

Create or Delete Primary Dos Partition.
Activate or Deactivate Primary Dos Partition.
Create or Delete Extended Dos Partition.
Create or Delete Logical Drives.
Delete Non-Dos Partitions.
Change Fixed Disk

In this article, we will not be concentrating on initialising new hard disks, but rather the basics of FDISK operation. Otherwise, it would have been a LOT more than 2-3 pages! (Note: I actually wrote a chapter of an upcoming booklet about initialising and setting up your hard drive for MS-DOS with FDISK and it came to 5 pages including screenshots)

So, without further adue, let me introduce you to the world of.....

FDISK & Partitioning:

Partitioning is one of the necessary steps to prepare a drive for use. It is the process of defining certain areas of the hard disk for the operating system to use. A volume is a section of the drive with a letter, like C: or D:. All hard drives must be partitioned, even if they will have only one partition, otherwise you wouldn't be able to use it.

A partition program writes a master partition boot sector to cylinder 0, head 0, sector 1. The data in this sector defines the start and end locations of each of the other partitions. It also indicates which of these partitions is active, or bootable, thus telling the computer where to look for the operating system.

All systems can handle 24 partitions, either spread out on the same drive or many drives. This means that one can have up to 24 different hard drives, according to DOS. DOS can't recognize more than 24 partitions (though there was the rumour that it could support up to 128 disk drives), although some other operating systems may. The limiting factor is simply the availability of letters. All partitions must have a letter. There are 26 letters, A: and B: are reserved for floppy drives, leaving 24 letters available.
Although there are third party partitioning programs that boast added capabilities, DOS FDISK is the accepted program for partitioning. FDISK sets up the partition in an optimum way and allows more than one operating system (OS) to reside on one system.

FDISK only shows two DOS partitions, the primary partition and the extended partition. The extended partition is divided into logical DOS volumes, each being a separate partition. The minimum partition size is one megabyte, due to the fact that FDISK in DOS 4.0 or later creates partitions based on numbers of MB. Partition size is usually limited to 2G. DOS versions earlier than 4.0 allow max partitions of 32 MB. Using the FAT32 system under DOS 7 and Windows 95 OSR2, max partition size is kicked up to 2 TB (2 TB = 2048 GB = 2,097,152 MB = 2,147,483,648 KB = 2,199,023,255,552 bytes).

When you start up FDISK from the command line (usually "C:\FDISK [Enter]") you will be presented with the following screen:

For owners of hard drives (over 2GB) you will want to enable LBA support within the program, so press "Y" and press [Enter]. Then you will see everybody's favourite screen:

From here you can select what you want FDISK to do and how. A brief explanation of the FDISK menu is as follows:

[1] Create DOS Partition or Logical DOS Drive

From this menu, you are free to create and manage any of your partitions.

[2] Set Active partition

This options allows to create the "Active" partition, or the first partition that the BIOS will look for when wanting to load your operating system.

[3] Delete Partition of Logical DOS Drive

From here you can do the "Evil of all Evil"; delete a partition. WARNING: This action is irreversible and can NOT be undone. However, the data is still recoverable, but if you know how to do that, why are you reading this at all?

[4] Display Partition information

Within door number #4, you can view the partition side of things regarding to you hard drive. Go on, take a peek, we wont tell :)

[5] Fixed Disk # (to be clarified)

This is usually only seen when you have more than one hard disk in your system at any time. Unfortunately, I've never seen this, so the No Joy Award goes to me :)

Favourite Command Line Parameters:
FDISK [/STATUS] /X

/STATUS Displays partition information.

/X Ignores extended disk-access support (will not use LBA support). Use this switch if you receive one of the following symptoms: Unable to access a drive from DOS versions prior to 7. Disk access messages . Stack overflow messages. High amounts of data corruption. Extra drive letters

Secret (undocumented) FDISK Switches:
FDISK /MBR - Command used to rewrite the Master Boot Record.
FDISK /CMBR - Recreate Master Boot Record on specified disk. Performs the same functions as FDISK /MBR except can be used on other disk drives.
FDISK 1/PRI:100 - Command line to create a 100 meg DOS partition on hard drive 1.
FDISK 1/EXT:500 - Command line to create a 500 meg extended DOS partition on hard drive 1.
FDISK 1/LOG:250 - Command line to create a 250 logical drives.
FDISK /PARTN - Saves the partition to a file called PARTSAV.FIL
FDISK /Q - Prevents fdisk from booting the system automatically after exiting fdisk.
FDISK /STATUS - Shows you the current status of your hard drives.
FDISK /ACTOK - Makes FDISK not check the disk integrity allowing the drives to be created faster.
FDISK /FPRMT - Will not get the prompt for FAT32 support, in addition allows FDISK to be forced into using FAT32 on drives smaller then 540MB (by default FDISK will not use FAT32 on any drive smaller then 540MB). Finally this command can only be used with FDISK that supports FAT32.

Multi-Booting:

If you're into multi-booting, again, why are you reading this??

Conclusion:

I hope this has given you some insight into how FDISK works and how to utilise it to your advantage. But a final warning, before attempting ANY partitioning on your computer, BACK UP everything on your system FIRST. This is meant to be a guide only. If you are unsure about any factor of partitioning and using FDISK, please consult a knowledgable friend. Be safe, be sure and your computer will return to you many hours of joy (yeah, the frustration comes free as well. Aren't we so lucky?)
Till next time!

If you'd like to see a more detailed walk through FDISK let me know and I'll write a sequel article to this. My email address is up the top.

Martin

Linked at TechTutorials