fdisk" -- Command" "

Hard-disk partitioning utility

//eettcc//ffddiisskk [[--rr]] [[--cc]] [[--bb _m_b_o_o_t]] _x_d_e_v ...

The command fdisk lets you view how a hard disk is partitioned, alter how it is partitioned, and mark a partition so that the COHERENT bootstrap will automatically boot the operating system it contains. If you wish, you can use fdisk to assign partitions to different operating systems, e.g., MS-DOS, CP/M, Windows NT, COHERENT, and XENIX.

fdisk recognizes the following command-line options:

--bb: Use the first 446 bytes of the file mboot to replace the bootstrap information in xdev. Use this option to overwrite the COHERENT bootstrap with another bootstrap.
--cc: Specify the disk geometry (i.e., number of cylinders, heads, sectors) for disk drives that your system's BIOS does not support.
--rr: Read-only access. fdisk reads the partition table and displays its contents, but does not let you change how a disk is partitioned. This is the ``safe'' option.
--VV: Display the version number of fdisk. PP When you invoke fdisk, it reads the first block from the special device xdev, which holds the partitioning information for that disk. xdev is the device whose name ends in x; for example, if you have one SCSI hard disk and one AT-style hard disk installed in your machine, xdev would be either /dev/sd0x or /dev/at0x. If you use fdisk with a device other than the x device (e.g., with device /dev/at0a), fdisk displays values for your partitions that are totally bogus -- and probably quite alarming.

After you invoke fdisk, it displays a warning message, then the layout of the disk whose partition-table device you named on the command line. The following gives an example layout, for a 33-megabyte AT disk:

     Drive 0 Currently has the following logical partitions:
                   [In Cylinders] [  In Tracks  ]
     Number  Type  Start End Size Start  End Size Mbyte Blocks Name
     0 Boot MS-DOS    0  149  150     0  899  900  7.83  15300 /dev/at0a
     1     EXT-DOS  150  614  464   900 3684 2784 24.28  47430 /dev/at0b
     2      UNUSED    0    0    0     0    0    0     0      0 /dev/at0c
     3      UNUSED    0    0    0     0    0    0     0      0 /dev/at0d

In this example, partition 1 (which is accessed via device /dev/at0a) holds an MS-DOS file system. It is marked as the ``Boot'' partition, which means that the COHERENT bootstrap will boot its operating system automatically when you reboot your computer. The other columns show the size of each partition, and its beginning and end points in both cylinders and tracks.

If you invoked fdisk with its option -r, the program exits at this point. If you did not invoke it with option -r, it displays the following menu of actions:

     Possible actions:
        0 = Quit
        1 = Change active partition (or make no partition active)
        2 = Change one logical partition
        3 = Change all logical partitions
        4 = Delete one logical partition
        5 = Change drive characteristics
        6 = Display drive information
        7 = Proceed to next drive

The following describes each action in detail:

00..: Quit fdisk.
11..: Change which partition is the active partition. You can also say that your system has no active partition. If you do so, the COHERENT bootstrap will prompt you at boot time to enter the number of the partition whose operating system you wish to boot. fdisk will let you set only one active partition at a time.
22..: Change the dimensions (i.e., the size, beginning point, or end point) of one partition. Doing this destroys the data on that partition.
33..: Change the dimensions of every partition. Doing this destroys the data on your hard disk.
44..: Delete a partition.
55..: Change the parameters of the drive. Use this option if COHERENT somehow has a faulty notion of your disk's size. You should never have to use this option; using it will wipe out all data on your hard disk.
66..: Give summary information about the disk -- that is, re- display the table shown above.
77..: This option appears only if you have more than one hard disk drive. Use this option to display information about another hard disk on your system.

Before you change the dimensions of any partition on your system, read the warnings given in the notes below. When you have finished modifying your disk, fdisk then writes your changes into xdev.

Files

&&lltt;;ffddiisskk..hh&&ggtt;;

Notes

If you change a device's partition table, reboot your system. Most device drivers will not recognize the revised partition information until a reboot occurs.

A As the --rr and --bb options are contradictory, attempting to use them together triggers an error message.

A Note that many operating systems implement a program named fdisk. Each manipulates a hard disk's partition table, but not all respect the fact that a disk may hold more than one operating system. In particular, the MS-DOS edition of fdisk can rearrange the order of entries in the partition table. If this happens, you may lose the ability to run COHERENT until the table is restored to its previous order. A sign of this problem is seeing the prompt AT boot? when you try to start COHERENT after running any fdisk program, and not being able to get past it.

A Computer systems that use older releases of a BIOS may report incorrect disk parameters. Users of such systems should change the CMOS setup values if possible, but the BIOS on some older systems will not allow you to specify arbitrary values for disk parameters. Users with such systems can use the option ffddiisskk --cc option instead.

A If you plan to install and run COHERENT and MS-DOS on the same hard disk, note the following:

+o: If you wish to install COHERENT and MS-DOS on the same hard drive, you must run the MS-DOS ffddiisskk first!
+o: If you plan on running both operating systems, you must install MS-DOS first and leave some free cylinders on the disk for COHERENT as well as a free partition. You can have both primary as well as extended MS-DOS partitions on the same drive as COHERENT, but COHERENT cannot use a sub-partition of the MS-DOS extended partition. COHERENT must have one of the four real partitions. Failure to observe these rules will result in loss of data! Caveat utilitor.

fdisk" -- Command" "

Files

See Also

Notes