fdisk: improve the description of -c and -u options on man page
Also doublespace sentences, hyphenate compound adjectives, alphabetize the options (except for -CHS), and further tweak some descriptions. Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
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Benno Schulenberg
Karel Zak
parent
2f8f138883
commit
a1939d7080
127
fdisk/fdisk.8
127
fdisk/fdisk.8
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@ -3,7 +3,7 @@
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.\" May be distributed under the GNU General Public License
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.TH FDISK 8 "11 June 1998" "Linux 2.0" "Linux Programmer's Manual"
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.SH NAME
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fdisk \- Partition table manipulator for Linux
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fdisk \- partition table manipulator for Linux
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.SH SYNOPSIS
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.B fdisk
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.RB [ \-uc ]
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@ -30,32 +30,32 @@ fdisk \- Partition table manipulator for Linux
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.SH DESCRIPTION
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.B fdisk
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(in the first form of invocation)
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is a menu driven program for creation and manipulation of
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is a menu-driven program for creation and manipulation of
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partition tables.
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It understands DOS type partition tables and BSD or SUN type disklabels.
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It understands DOS-type partition tables and BSD- or SUN-type disklabels.
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.B fdisk
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does not understand GUID Partition Table (GPT) and
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it is not designed for large partitions. In particular case use more advanced GNU
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does not understand GUID partition tables (GPTs) and it is not designed
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for large partitions. In these cases, use the more advanced GNU
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.BR parted (8).
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.B fdisk does not use DOS-compatible mode and cylinders
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as display units by default. The old deprecated DOS behavior could be
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enabled by '-cdos -ucyl' command line options.
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.B fdisk
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does not use DOS-compatible mode and cylinders as display units by default.
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The old deprecated DOS behavior can be enabled with
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the '-c=dos -u=cylinders' command-line options.
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Hard disks can be divided into one or more logical disks called
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.IR partitions .
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This division is described in the
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.I "partition table"
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This division is recorded in the
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.IR "partition table" ,
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found in sector 0 of the disk.
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In the BSD world one talks about `disk slices' and a `disklabel'.
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(In the BSD world one talks about `disk slices' and a `disklabel'.)
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Linux needs at least one partition, namely for its root file system.
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It can use swap files and/or swap partitions, but the latter are more
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efficient. So, usually one will want a second Linux partition
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efficient. So, usually one will want a second Linux partition
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dedicated as swap partition.
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On Intel compatible hardware, the BIOS that boots the system
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On Intel-compatible hardware, the BIOS that boots the system
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can often only access the first 1024 cylinders of the disk.
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For this reason people with large disks often create a third partition,
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just a few MB large, typically mounted on
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@ -68,56 +68,53 @@ or testing, to use more than the minimum number of partitions.
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.SH DEVICES
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The
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.I device
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is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk.
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The old systems without libata (a library used inside the Linux kernel to
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is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk.
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Old systems without libata (a library used inside the Linux kernel to
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support ATA host controllers and devices) make a difference between IDE and
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SCSI disks. In such a case the device name will be /dev/hd* (IDE) or /dev/sd*
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SCSI disks. In such cases the device name will be /dev/hd* (IDE) or /dev/sd*
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(SCSI).
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The
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.I partition
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is a
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.I device
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name followed by a partition number. For example,
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.B /dev/sda1
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is a device name followed by a partition number. For example, /dev/sda1
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is the first partition on the first hard disk in the system.
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See also Linux kernel documentation (the Documentation/devices.txt file).
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.SH DISK LABELS
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A BSD/SUN type disklabel can describe 8 partitions,
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A BSD/SUN-type disklabel can describe 8 partitions,
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the third of which should be a `whole disk' partition.
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Do not start a partition that actually uses its first sector
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(like a swap partition) at cylinder 0, since that will
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destroy the disklabel.
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An IRIX/SGI type disklabel can describe 16 partitions,
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An IRIX/SGI-type disklabel can describe 16 partitions,
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the eleventh of which should be an entire `volume' partition,
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while the ninth should be labeled `volume header'.
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The volume header will also cover the partition table, i.e.,
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it starts at block zero and extends by default over five cylinders.
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The remaining space in the volume header may be used by header
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directory entries. No partitions may overlap with the volume header.
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Also do not change its type and make some file system on it, since
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Also do not change its type or make some filesystem on it, since
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you will lose the partition table. Use this type of label only when
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working with Linux on IRIX/SGI machines or IRIX/SGI disks under Linux.
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A DOS type partition table can describe an unlimited number
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of partitions. In sector 0 there is room for the description
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of 4 partitions (called `primary'). One of these may be an
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A DOS-type partition table can describe an unlimited number
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of partitions. In sector 0 there is room for the description
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of 4 partitions (called `primary'). One of these may be an
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extended partition; this is a box holding logical partitions,
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with descriptors found in a linked list of sectors, each
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preceding the corresponding logical partitions.
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The four primary partitions, present or not, get numbers 1-4.
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Logical partitions start numbering from 5.
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In a DOS type partition table the starting offset and the size
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In a DOS-type partition table the starting offset and the size
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of each partition is stored in two ways: as an absolute number
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of sectors (given in 32 bits) and as a Cylinders/Heads/Sectors
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triple (given in 10+8+6 bits). The former is OK - with 512-byte
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sectors this will work up to 2 TB. The latter has two different
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problems. First of all, these C/H/S fields can be filled only
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of sectors (given in 32 bits), and as a Cylinders/Heads/Sectors
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triple (given in 10+8+6 bits). The former is OK -- with 512-byte
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sectors this will work up to 2 TB. The latter has two
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problems. First, these C/H/S fields can be filled only
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when the number of heads and the number of sectors per track
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are known. Secondly, even if we know what these numbers should be,
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are known. And second, even if we know what these numbers should be,
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the 24 bits that are available do not suffice.
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DOS uses C/H/S only, Windows uses both, Linux never uses C/H/S.
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@ -127,19 +124,19 @@ will obtain the disk geometry automatically. This is not
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necessarily the physical disk geometry (indeed, modern disks do not
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really have anything like a physical geometry, certainly not something
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that can be described in simplistic Cylinders/Heads/Sectors form),
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but is the disk geometry that MS-DOS uses for the partition table.
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but it is the disk geometry that MS-DOS uses for the partition table.
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Usually all goes well by default, and there are no problems if
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Linux is the only system on the disk. However, if the disk has
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Linux is the only system on the disk. However, if the disk has
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to be shared with other operating systems, it is often a good idea
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to let an fdisk from another operating system make at least one
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partition. When Linux boots it looks at the partition table, and
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partition. When Linux boots it looks at the partition table, and
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tries to deduce what (fake) geometry is required for good
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cooperation with other systems.
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Whenever a partition table is printed out, a consistency check is performed
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on the partition table entries. This check verifies that the physical and
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logical start and end points are identical, and that the partition starts
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logical start and end points are identical, and that each partition starts
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and ends on a cylinder boundary (except for the first partition).
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Some versions of MS-DOS create a first partition which does not begin
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@ -147,11 +144,11 @@ on a cylinder boundary, but on sector 2 of the first cylinder.
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Partitions beginning in cylinder 1 cannot begin on a cylinder boundary, but
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this is unlikely to cause difficulty unless you have OS/2 on your machine.
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A sync() and a BLKRRPART ioctl() (reread partition table from disk)
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A sync() and an ioctl(BLKRRPART) (reread partition table from disk)
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are performed before exiting when the partition table has been updated.
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Long ago it used to be necessary to reboot after the use of fdisk.
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I do not think this is the case anymore - indeed, rebooting too quickly
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might cause loss of not-yet-written data. Note that both the kernel
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I do not think this is the case anymore -- indeed, rebooting too quickly
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might cause loss of not-yet-written data. Note that both the kernel
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and the disk hardware may buffer data.
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.SH "DOS 6.x WARNING"
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@ -186,20 +183,17 @@ program and Linux partitions with the Linux fdisk or Linux cfdisk program.
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.SH OPTIONS
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.TP
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.BI "\-b " sectorsize
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Specify the sector size of the disk. Valid values are 512, 1024, 2048 or 4096.
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(Recent kernels know the sector size. Use this only on old kernels or
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to override the kernel's ideas.) Since util-linux-ng 2.17 fdisk differentiates
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between logical and physical sector size. This option changes both sector sizes to
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Specify the sector size of the disk. Valid values are 512, 1024, 2048 or 4096.
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(Recent kernels know the sector size. Use this only on old kernels or
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to override the kernel's ideas.) Since util-linux-ng-2.17, fdisk differentiates
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between logical and physical sector size. This option changes both sector sizes to
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.IB sectorsize .
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.TP
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.BI \-h
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Print help and then exit.
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.TP
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.BI "\-c"[=mode]
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Specifies the compatiblity mode, 'dos' or 'nondos' mode. The default is non-DOS
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compatibility mode. For backward compatibility the option is possible to use
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without <mode> argument, then the default is used. Note that the optional
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<mode> argument cannot be separated from the -c option by space, the correct
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Specify the compatiblity mode, 'dos' or 'nondos'. The default is non-DOS
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mode. For backward compatibility, it is possible to use the option without
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the <mode> argument -- then the default is used. Note that the optional
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<mode> argument cannot be separated from the -c option by a space, the correct
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form is for example '-c=dos'.
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.TP
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.BI "\-C " cyls
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@ -207,7 +201,7 @@ Specify the number of cylinders of the disk.
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I have no idea why anybody would want to do so.
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.TP
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.BI "\-H " heads
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Specify the number of heads of the disk. (Not the physical number,
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Specify the number of heads of the disk. (Not the physical number,
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of course, but the number used for partition tables.)
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Reasonable values are 255 and 16.
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.TP
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@ -217,23 +211,24 @@ Specify the number of sectors per track of the disk.
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partition tables.)
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A reasonable value is 63.
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.TP
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.BI \-h
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Print help and then exit.
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.TP
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.B \-l
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List the partition tables for the specified devices and then exit.
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If no devices are given, those mentioned in
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.I /proc/partitions
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(if that exists) are used.
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.TP
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.BI "\-u"[=unit]
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When listing partition tables, give sizes in 'sectors' or in 'cylinders'. The
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default is to give sizes in sectors. For backward compatibility the option is
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possible to use without <units> argument, then the default is used. Note that
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the optional <unit> argument cannot be separated from the -u option by space,
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the correct form is for example '-u=cylinders'.
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.BI "\-s " partition...
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Print the size (in blocks) of each given partition.
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.TP
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.BI "\-s " partition
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The
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.I size
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of the partition (in blocks) is printed on the standard output.
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.BI "\-u"[=unit]
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When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The
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default is to show sizes in sectors. For backward compatibility, it is possible
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to use the option without the <units> argument -- then the default is used.
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Note that the optional <unit> argument cannot be separated from the -u option
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by a space, the correct form is for example '-u=cylinders'.
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.TP
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.B \-v
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Print version number of
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@ -250,14 +245,14 @@ Try them in the order
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.B cfdisk
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is a beautiful program that has strict requirements on
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the partition tables it accepts, and produces high quality partition
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tables. Use it if you can.
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tables. Use it if you can.
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.B fdisk
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is a buggy program that does fuzzy things - usually it happens to
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produce reasonable results. Its single advantage is that it has
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produce reasonable results. Its single advantage is that it has
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some support for BSD disk labels and other non-DOS partition tables.
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Avoid it if you can.
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.B sfdisk
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is for hackers only - the user interface is terrible, but it is
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is for hackers only -- the user interface is terrible, but it is
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more correct than fdisk and more powerful than both fdisk and cfdisk.
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Moreover, it can be used noninteractively.)
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.PP
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@ -266,7 +261,7 @@ These days there also is
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The cfdisk interface is nicer, but parted does much more: it not only
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resizes partitions, but also the filesystems that live in them.
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.PP
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The IRIX/SGI type disklabel is currently not supported by the kernel.
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The IRIX/SGI-type disklabel is currently not supported by the kernel.
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Moreover, IRIX/SGI header directories are not fully supported yet.
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.PP
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The option `dump partition table to file' is missing.
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