fdisk

Create and manage partitions on a hard disk

Note: In order to run this utility, you must be logged in as root or have read/write permissions for the block-special file concerned.

Syntax:

fdisk [-fz] [-B loader] drive [cmd [args]]

Runs on:

QNX Neutrino

Options:

-B loader: Specifies the 512-byte file that the loader command writes to the disk.
-f: Force the boot loader to be written on command, even if it isn't possible to save an existing old loader to a mounted filesystem. In non-interactive mode, execute the given add command, even if this would involve overwriting an existing partition slot.
-z: Zero the partition table (interactive mode only).
drive: The disk drive to partition. This must name a block-special file (e.g., /dev/hd0).
cmd [args]: An fdisk command, as described below.

Description:

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.

CAUTION:

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.

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

devb-eide &

You should then execute the fdisk command to partition your disk. For example:

fdisk /dev/hd0 add -t 179 -p 50

New or changed partitions aren't immediately recognized and/or mounted. 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
7	Windows NT^a	fs-nt.so	N/A	N/A
11, 12, or 14	FAT32	fs-dos.so	mkdosfs	chkdosfs
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

^a Read-only.

^b Not usually necessary.

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:

add [args]

Add a new partition entry of the size and type specified. If fdisk can't locate sufficient unallocated disk space to satisfy your request, it allocates the largest available portion of the disk (if any). Here are the arguments for add:

-b: Make the added partition bootable. If another partition was already flagged as the primary boot partition, the flag is turned off for it.
-c start,end: The start and end for the partition to use.
-e extended_slot: The index into the extended partition (1–N).
-l: (“el”) Use blocks instead of cylinders as the units.
-n count: The number of cylinders to allocate (extended partitions only).
-p percent: The percentage of the largest contiguous space the added partition should use. The default is 100%.
If you specify the -c option, the -p option is ignored.
-s slot: The slot (1-4) in the partition table to use. The default is the first free slot.
-t type: The type of partition to add (0–255). The default is 178 (Power-Safe filesystem).

Note that extended partition indexes may change due to additions.

boot [args]

Turn on the boot flag for the indicated partition. If another partition was already flagged as the primary boot partition, the flag is turned off for it. Here are the arguments for boot:

-s slot: Boot the partition in the selected slot.
-t type: Boot the partition of the selected type.

delete [args]

Delete the specified partitions. Here are the arguments for delete:

-a: Delete all partitions.
-e extended_slot: The index into the extended partition (1–N).
-s slot: Delete the partition in the selected slot.
-t type: Delete this type of partition.

Note that extended partition indexes may change due to deletions.

info

Show the mount information for the raw drive.

The fdisk utility uses a DCMD_CAM_DEVINFO devctl() command to obtain the cylinder, head, sectors per track, and total sectors counts. Multiplying the first three values together is the classic method of calculating the total number of sectors.

However, some hard drives employ zoned bit recording, so it's impossible to precisely map the number of sectors per track and other fields. As a result, the total number of sectors returned from devctl() and the total number of sectors that were calculated might not match. In this case, fdisk displays a warning.

loader

Write the QNX loader to the disk. You must specify the loader file name using -B on the command line or the operation will fail.

query [args]

Print the number of cylinders to standard output. Here are the arguments for query:

-e extended_slot: The index into the extended partition (1–N).
-f: Display the total number of free cylinders.
-l: (“el”) Use blocks instead of cylinders as the units.
-s slot: Query the partition in the selected slot.
-T: Display the total number of cylinders.
-t type: Query the partition of the selected type.

show [args]

Display the partition table. The argument for show is:

-l: (“el”) Use blocks instead of cylinders as the units.

Interactive mode

On some platforms, fdisk is a fullscreen, interactive program that's fairly self-explanatory. This mode requires a properly configured /usr/lib/terminfo directory structure and TERM environment variable.

When you invoke fdisk, you'll see a screen similar to this one (assuming your disk is already partitioned):

FDISK
Ignore Next Prev 1 2 3 4 Change Delete Boot Unboot Restore Loader Save Quit

        _____OS_____     Start      End     ______Number_____    Size    Boot
        name    type    Cylinder  Cylinder  Cylinders  Blocks

--> 1.  QNX6   (177)          0      7648      7649   122881122  60000 MB
    2.  QNX6   (178)       7649      9963      2315    37190475  18159 MB  *
    3.  ______ (___)    _______   _______   _______   _________  _____
    4.  ______ (___)    _______   _______   _______   _________  _____


 Choose a partition by typing the partition number OR moving the pointer
 with the UP/DOWN arrows.
 Then, choose one of the actions on the top line of the screen.



Drive : /dev/hd0                    Config:   255 Heads
Size  : 78159 Mbytes                           63 Sectors/track
Loader: Unknown                              9964 Cylinders
                                              512 Block Size

                                    Last cylinder is 9963

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.

The commands are:

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 partition table from the disk for editing.
Loader	Change the bootstrap loader to the QNX loader. You must specify the loader file name using -B on the command line or the operation will fail.
Save	Save all changes and quit. This writes to the device and is irrevocable.
Quit	Quit without saving changes.

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

fdisk /dev/hd0 add -b -t 179 -p 50
mount -e /dev/hd0
mkqnx6fs /dev/hd0t179
mount -t qnx6 /dev/hd0t179 /mnt/psfs

Exit status:

0: Success.
>0: An error occurred; fdisk writes error messages to standard error.

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.