partx(8) provides a rich interface for scripts to print disk layouts, fdisk is mostly designed for humans. Backward compatibility in the output of fdisk is not guaranteed. The input (the commands) should always be backward compatible.Davidlohr BuesoThe original version was written by Andries E. Brouwer, A. V. Le Blanc and others.
- -b, --sector-size sectorsize
- Specify the sector size of the disk. Valid values are 512, 1024, 2048, and 4096. (Recent kernels know the sector size. Use this option only on old kernels or to override the kernel's ideas.) Since util-linux-2.17, fdisk differentiates between logical and physical sector size. This option changes both sector sizes to sectorsize.
- -B, --protect-boot
- Don't erase the begin of the first disk sector when create a new disk label. This feature is supported for GPT and MBR.
- -c, --compatibility[=mode]
- Specify the compatibility mode, 'dos' or 'nondos'. The default is non-DOS mode. For backward compatibility, it is possible to use the option without the mode argument -- then the default is used. Note that the optional mode argument cannot be separated from the -c option by a space, the correct form is for example '-c=dos'.
- -h, --help
- Display a help text and exit.
- -L, --color[=when]
- Colorize the output. The optional argument when can be auto, never or always. If the when argument is omitted, it defaults to auto. The colors can be disabled; for the current built-in default see the --help output. See also the COLORS section.
- -l, --list
- List the partition tables for the specified devices and then exit. If no devices are given, those mentioned in /proc/partitions (if that file exists) are used.
- -o, --output list
- Specify which output columns to print. Use --help to get a list of all supported columns. The default list of columns may be extended if list is specified in the format +list (e.g. -o +UUID).
- -s, --getsz
- Print the size in 512-byte sectors of each given block device. This option is DEPRECATED in favour of blockdev(1).
- -t, --type type
- Enable support only for disklabels of the specified type, and disable support for all other types.
- -u, --units[=unit]
- When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The default is to show sizes in sectors. For backward compatibility, it is possible to use the option without the unit argument -- then the default is used. Note that the optional unit argument cannot be separated from the -u option by a space, the correct form is for example '-u=cylinders'.
- -C, --cylinders number
- Specify the number of cylinders of the disk. I have no idea why anybody would want to do so.
- -H, --heads number
- Specify the number of heads of the disk. (Not the physical number, of course, but the number used for partition tables.) Reasonable values are 255 and 16.
- -S, --sectors number
- Specify the number of sectors per track of the disk. (Not the physical number, of course, but the number used for partition tables.) A reasonable value is 63.
- -w, --wipe when
- Wipe filesystem, RAID and partition-table signatures from the device, in order to avoid possible collisions. The argument when can be auto, never or always. When this option is not given, the default is auto, in which case signatures are wiped only when in interactive mode. In all cases detected signatures are reported by warning messages before a new partition table is created. See also wipefs(8) command.
- -W, --wipe-partition when
- Wipe filesystem, RAID and partition-table signatures from a newly created partitions, in order to avoid possible collisions. The argument when can be auto, never or always. When this option is not given, the default is auto, in which case signatures are wiped only when in interactive mode and after confirmation by user. In all cases detected signatures are reported by warning messages before a new partition is created. See also wipefs(8) command.
- -V, --version
- Display version information and exit.
GPT is modern standard for the layout of the partition table. GPT uses 64-bit logical block addresses, checksums, UUIDs and names for partitions and an unlimited number of partitions (although the number of partitions is usually restricted to 128 in many partitioning tools). Note that the first sector is still reserved for a protective MBR in the GPT specification. It prevents MBR-only partitioning tools from mis-recognizing and overwriting GPT disks. GPT is always a better choice than MBR, especially on modern hardware with a UEFI boot loader.DOS-type (MBR)
A DOS-type partition table can describe an unlimited number of partitions. In sector 0 there is room for the description of 4 partitions (called `primary'). One of these may be an extended partition; this is a box holding logical partitions, with descriptors found in a linked list of sectors, each preceding the corresponding logical partitions. The four primary partitions, present or not, get numbers 1-4. Logical partitions are numbered starting from 5. In a DOS-type partition table the starting offset and the size of each partition is stored in two ways: as an absolute number of sectors (given in 32 bits), and as a Cylinders/Heads/Sectors triple (given in 10+8+6 bits). The former is OK -- with 512-byte sectors this will work up to 2 TB. The latter has two problems. First, these C/H/S fields can be filled only when the number of heads and the number of sectors per track are known. And second, even if we know what these numbers should be, the 24 bits that are available do not suffice. DOS uses C/H/S only, Windows uses both, Linux never uses C/H/S. The C/H/S addressing is deprecated and may be unsupported in some later fdisk version. Please, read the DOS-mode section if you want DOS-compatible partitions. fdisk does not care about cylinder boundaries by default.BSD/Sun-type
A BSD/Sun disklabel can describe 8 partitions, the third of which should be a `whole disk' partition. Do not start a partition that actually uses its first sector (like a swap partition) at cylinder 0, since that will destroy the disklabel. Note that a BSD label is usually nested within a DOS partition.IRIX/SGI-type
An IRIX/SGI disklabel can describe 16 partitions, the eleventh of which should be an entire `volume' partition, while the ninth should be labeled `volume header'. The volume header will also cover the partition table, i.e., it starts at block zero and extends by default over five cylinders. The remaining space in the volume header may be used by header directory entries. No partitions may overlap with the volume header. Also do not change its type or make some filesystem on it, since you will lose the partition table. Use this type of label only when working with Linux on IRIX/SGI machines or IRIX/SGI disks under Linux.A sync() and an ioctl(BLKRRPART) (rereading the partition table from disk) are performed before exiting when the partition table has been updated. dd(1) to zero the first 512 bytes of that partition before using DOS FORMAT to format the partition. For example, if you were using fdisk to make a DOS partition table entry for /dev/sda1, then (after exiting fdisk and rebooting Linux so that the partition table information is valid) you would use the command "dd if=/dev/zero of=/dev/sda1 bs=512 count=1" to zero the first 512 bytes of the partition. fdisk usually obtains the disk geometry automatically. This is not necessarily the physical disk geometry (indeed, modern disks do not really have anything like a physical geometry, certainly not something that can be described in the simplistic Cylinders/Heads/Sectors form), but it is the disk geometry that MS-DOS uses for the partition table. Usually all goes well by default, and there are no problems if Linux is the only system on the disk. However, if the disk has to be shared with other operating systems, it is often a good idea to let an fdisk from another operating system make at least one partition. When Linux boots it looks at the partition table, and tries to deduce what (fake) geometry is required for good cooperation with other systems. Whenever a partition table is printed out in DOS mode, a consistency check is performed on the partition table entries. This check verifies that the physical and logical start and end points are identical, and that each partition starts and ends on a cylinder boundary (except for the first partition). Some versions of MS-DOS create a first partition which does not begin on a cylinder boundary, but on sector 2 of the first cylinder. Partitions beginning in cylinder 1 cannot begin on a cylinder boundary, but this is unlikely to cause difficulty unless you have OS/2 on your machine. For best results, you should always use an OS-specific partition table program. For example, you should make DOS partitions with the DOS FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk programs. terminal-colors.d(5) for more details about colorization configuration. The logical color names supported by fdisk are:
- The header of the output tables.
- The help section titles.
- The warning messages.
- The welcome message.
- enables fdisk debug output.
- enables libfdisk debug output.
- enables libblkid debug output.
- enables libsmartcols debug output.
- use visible padding characters. Requires enabled LIBSMARTCOLS_DEBUG.