The fdisk utility lets you create and manage partitions on a hard disk (typically a rotating medium, but fdisk works on other devices, such as compact flash and USB flash, if they support PC-style Master Boot Records (MBRs) and partitions). The partition information, which is kept in the disk's first physical block, matches that used by DOS.

On some platforms, fdisk supports a full-screen interface; see “Interactive mode,” below.

The installer for Microsoft Windows overwrites any existing Master Boot Record with its own. If you want your disk to contain bootable DOS and bootable QNX (or other non-DOS) partitions, you should install Windows first, and then create the other partitions. If you create a QNX partition first and then install Windows, you can restore the boot loader by running QNX Neutrino from the installation disk and explicitly using dloader.
On some x86 machines, you can boot only from OS images that are loaded from within the first 1024 cylinders of the disk. This means that while you may be able to initially install and boot from a partition which extends past the 1024th cylinder, it will someday fail when you go to update the boot image because the location of some of its blocks may change. When this happens you will have a system that's no longer bootable.
Avoid this problem by creating a separate partition to boot from that lies entirely within the first 1024 cylinders of the hard drive, and use a second partition to access the additional space on the drive. (The boot partition may be quite small — just a few megabytes will suffice.)

Before creating a QNX 4 partition for the first time, you must first start the hard disk driver:

The QNX 4 filesystem doesn't automatically relearn any changes that you make to the partition table with fdisk. You must either slay and restart the filesystem/driver (devb-*), use mount -e /dev/hd0 to recognize the new partitions and update the contents of /dev, or reboot.

Partition types

The fdisk utility recognizes the following partition types. If you add a partition, use the command shown to initialize it.

Type	Filesystem	Shared object	Initialize with:	Check with:
1, 4, or 6	DOS	`fs-dos.so`	`mkdosfs`	`chkdosfs`
5	DOS extended	N/A	N/A	N/A
7	Windows NT^a	`fs-nt.so`	N/A	N/A
8 or 9	QNX 2	N/A	N/A	N/A
11, 12, or 14	FAT32	`fs-dos.so`	`mkdosfs`	`chkdosfs`
15	Windows 95 extended	N/A	N/A	N/A
77, 78, or 79	QNX 4	`fs-qnx4.so`	`dinit`	`chkfsys`
99	UNIX	N/A	N/A	N/A
130	Linux swap	N/A	N/A	N/A
131	Linux (Ext2)	`fs-ext2.so`	N/A	N/A
133 or 147	Linux extended	N/A	N/A	N/A
165	BSD	N/A	N/A	N/A
175	Apple Macintosh HFS or HFS Plus^a	`fs-mac.so`	N/A	N/A
177, 178, or 179	Power-Safe	`fs-qnx6.so`	`mkqnx6fs`	`chkqnx6fs`^b

For more information, see the Filesystems chapter of the System Architecture guide.

Commands

The fdisk utility supports the following commands directly from the command line:

Interactive mode

On some platforms, fdisk is a fullscreen, interactive program that's fairly self-explanatory. When you invoke fdisk, you'll see a screen similar to this one (assuming your disk is already partitioned):

You'll see the available commands displayed at the top of the screen. To select a command, either type its first letter or move the cursor to the command (with the arrow keys) and press Enter.

Command:	Action:
`Next`	Move the pointer to the next entry.
`Prev`	Move the pointer to the previous entry.
`1`, `2`, `3`, or `4`	Move the pointer to the indicated entry.
`Change`	Change the selected partition (see below).
`Delete`	Delete the selected partition.
`Boot`	Turn on the boot flag for the selected partition. If another partition was already flagged as the primary boot partition, the flag is turned off for it.
`Unboot`	Turn off the boot flag for the selected partition.
`Restore`	Restore the previous non-QNX bootstrap loader.
`Loader`	Change the bootstrap loader to the QNX loader.
`Save`	Save all changes and quit. This writes to the device and is irrevocable.
`Quit`	Quit without saving changes.

If you're changing a partition entry, note the following:

Save the details about the partition (e.g. by writing them on a piece of paper), because fdisk blanks the fields as you edit them.
You have to enter the partition's type number and the start and end cylinders; fdisk calculates the other information for you. Press Enter after typing each value.
If the partition was bootable before you changed it, use the Boot command to make it bootable again.

Examples:

Create a QNX 4 partition that occupies half the disk, or the largest available space if there isn't a space big enough for a new partition that occupies half the disk:

Continuing from either of the above examples, reread the partition table, set up a QNX 4 filesystem on the new partition, and then mount it:

Create a bootable partition for a Power-Safe filesystem, reread the partition table, format the new partition, and then mount it:

Exit status:

Caveats:

After changing any partition information, you must either slay and restart the filesystem/driver (devb-*) or use mount -e to make the filesystem reread the partition table.

`fdisk`

Syntax:

Runs on:

Options: