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Fdisk: special switches to make Fdisk perform better

by Bob Wright

Special Switches

by Bob Wright

Special Switches for MS FDISK
The HELP file and Microsoft web site is rather vague about special switches for MS FDISK. No reason for you to be in the dark, so here are the known switches:

FDISK Switch Definitions

/STATUS - Show current partition layout
If you have an extended partition with no logical drive defined, no information about the extended partition is shown.

/MBR - Recreate Master Boot Record on disk 1
This function is handy when an virus has infected the Master Boot Record. With /MBR you can wipe-out the virus. FDISK /MBR

/PRI - Create primary partition. Partition is set to active
Create a primary partition on disk number with the size of . The partition is set to active.
If is larger than the space on the HD all space is used for the primary partition.

/PRIO - Create primary partition with FAT16/FAT32 override. Partition is set to active Works as /PRI.

/EXT - Create extended partition
Create an extended partition (to hold logical drives) on disk number with the size of .
If is larger than remaining free space, all free space is used. That is, you don’t have to know the exact remaining size in order to use this switch.

/LOG - Create logical drive
With /LOG you create a logical drive with the size of . /LOG must be used together with /EXT.

/LOG must be used together with /EXT and must be the same for both switches. Furthermore, must be smaller or equal to free space.

/LOGO - Create logical drive with FAT16/FAT32 override
Works as /LOG.

/FPRMT - Prompt for FAT32/FAT16 in interactive mode
With /FPRMT you won't get the FDISK startscreen where you are asked for support for large disks. Instead, you will be promted for FAT16/FAT32 each time you create a partition. FDISK /FPRMT
Note that the prompt for FAT16/FAT32 will be available for ALL partitions, so this option can be used to force FDISK to create FAT 32 partitions smaller than 540Mb. (By default, FDISK uses FAT32 for partitions greater than 540Mb only).

/Q - Skip forced reboot on exit
With /Q the PC will not be rebooted after modifying the Partition Tables. However, I don't recall that DOS 7.x FDISK does a reboot. Maybe it's because I always use FDISK from a boot-floppy. FDISK /Q

/X - Do not use LBA partitions
With /X you won't get any LBA partitions. See Micro Firmware Technical Support for more details. FDISK /X

/ACTOK - Do not check drive integrity
With /ACTOK the integrity of drive is not checked making FDISK faster. FDISK /ACTOK

/CMBR - Recreate Master Boot Record on specified disk
Works as /MBR with the exception that you specify the disk to have it's MBR recreated. FDISK /CMBR

Notes on /PRI, /PRIO and /LOG, /LOGO
As far as I can tell, PRI and LOG creates FAT32 when partitions are larger than 512Mb and FAT16 when partitions are smaller than 512Mb. PRIO and LOGO creates FAT16 even if partitions are larger than 512Mb (in effect, it’s like FDISK from DOS 5/6).



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