How to Partition a Disk with FDISK on FreeDOS
A complete walkthrough creating a primary partition, an extended partition with logical drives, and setting the active boot partition — the way DOS disks have always been organized.
FDISK is FreeDOS’s tool for creating and managing disk partitions before formatting — this walks through the classic DOS partitioning model: one primary partition, an optional extended partition containing logical drives, and marking which partition is active for booting.
Step 1: launch FDISK
FDISKThis tool modifies partition tables directly — back up anything important on the target disk first. A mistake here can make existing data inaccessible.
Step 2: view existing partition information first
FDISK menu → option 4: Display partition informationAlways check the current state before making any changes — confirming what’s already there prevents accidentally repartitioning a disk you meant to leave alone, especially on a system with more than one physical disk installed.
Step 3: create a primary DOS partition
FDISK menu → option 1: Create DOS partition or Logical DOS Drive
→ option 1: Create Primary DOS PartitionFollow the prompts to specify size — FDISK will ask whether to use the maximum available space or a specific smaller size, useful if you’re planning to create additional partitions afterward.
Step 4: create an extended partition, if you want more than one partition
FDISK menu → option 1 → option 2: Create Extended DOS PartitionDOS’s partitioning scheme only supports a single primary partition per disk directly usable as a drive letter directly from the partition table — additional drive letters on the same physical disk come from logical drives inside an extended partition instead.
Step 5: create logical drives inside the extended partition
FDISK menu → option 1 → option 3: Create Logical DOS Drive(s)Each logical drive created here becomes an additional drive letter (D:, E:, and so on) once the disk is fully set up — useful for separating data from the system, or organizing a large disk into more manageable pieces.
Step 6: set the active partition
FDISK menu → option 2: Set Active PartitionExactly one partition must be marked active for the system to boot from that disk — this is almost always the primary partition, and a disk that “won’t boot” despite having a correctly installed OS is sometimes simply missing this step.
Step 7: exit FDISK and reboot
FDISK changes require a reboot to take effect before the
new partition layout is usable.Step 8: format each new partition/logical drive
FORMAT C: /S
FORMAT D:/S on the primary partition copies the system files needed to boot — logical drives intended purely for data don’t need this flag.
Step 9: verify the final layout
FDISK menu → option 4: Display partition informationConfirm the primary partition, extended partition, and any logical drives all appear as expected, with the correct partition marked active, before considering the disk fully set up.
Why the primary/extended/logical structure exists at all
This layered structure — one primary partition, an extended partition as a container for further subdivision — is a direct consequence of the original Master Boot Record partition table format only reserving space for four partition table entries total. Logical drives inside an extended partition were the mechanism DOS used to support more than four total “drives” on one physical disk within that structural constraint, and FDISK’s menu structure directly reflects this same primary/extended/logical model.