1 .\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu)
2 .\" Copyright 1998 Andries E. Brouwer (aeb@cwi.nl)
3 .\" Copyright 2012 Davidlohr Bueso <dave@gnu.org>
4 .\" Copyright (C) 2013 Karel Zak <kzak@redhat.com>
5 .\" May be distributed under the GNU General Public License
6 .TH FDISK 8 "February 2016" "util-linux" "System Administration"
9 fdisk \- manipulate disk partition table
21 is a dialog-driven program for creation and manipulation of partition tables.
22 It understands GPT, MBR, Sun, SGI and BSD partition tables.
24 Block devices can be divided into one or more logical disks called
26 This division is recorded in the
27 .IR "partition table" ,
28 usually found in sector 0 of the disk.
29 (In the BSD world one talks about `disk slices' and a `disklabel'.)
31 All partitioning is driven by device I/O limits (the topology) by default.
33 is able to optimize the disk layout for a 4K-sector size and use an alignment offset on
34 modern devices for MBR and GPT. It is always a good idea to follow \fBfdisk\fR's defaults
35 as the default values (e.g., first and last partition sectors) and partition
36 sizes specified by the +/-<size>{M,G,...} notation are always aligned according
37 to the device properties.
39 CHS (Cylinder-Head-Sector) addressing is deprecated and not used by default.
40 Please, do not follow old articles and recommendations with "fdisk -S <n> -H
41 <n>" advices for SSD or 4K-sector devices.
45 provides a rich interface for scripts to print disk layouts,
47 is mostly designed for humans. Backward compatibility in the output of
49 is not guaranteed. The input (the commands) should always be backward compatible.
53 \fB\-b\fR, \fB\-\-sector\-size\fR \fIsectorsize\fP
54 Specify the sector size of the disk. Valid values are 512, 1024, 2048, and 4096.
55 (Recent kernels know the sector size. Use this option only on old kernels or
56 to override the kernel's ideas.) Since util-linux-2.17, \fBfdisk\fR differentiates
57 between logical and physical sector size. This option changes both sector sizes to
60 \fB\-B\fR, \fB\-\-protect\-boot\fP
61 Don't erase the begin of the first disk sector when create a new disk label. This
62 feature is supported for GPT and MBR.
64 \fB\-c\fR, \fB\-\-compatibility\fR[=\fImode\fR]
65 Specify the compatibility mode, 'dos' or 'nondos'. The default is non-DOS
66 mode. For backward compatibility, it is possible to use the option without
67 the \fImode\fR argument -- then the default is used. Note that the optional
68 \fImode\fR argument cannot be separated from the \fB-c\fR option by a space,
69 the correct form is for example '-c=dos'.
71 \fB\-h\fR, \fB\-\-help\fR
72 Display a help text and exit.
74 \fB\-L\fR, \fB\-\-color\fR[=\fIwhen\fR]
75 Colorize the output. The optional argument \fIwhen\fP
76 can be \fBauto\fR, \fBnever\fR or \fBalways\fR. If the \fIwhen\fR argument is omitted,
77 it defaults to \fBauto\fR. The colors can be disabled; for the current built-in default
78 see the \fB\-\-help\fR output. See also the \fBCOLORS\fR section.
80 \fB\-l\fR, \fB\-\-list\fR
81 List the partition tables for the specified devices and then exit.
82 If no devices are given, those mentioned in
84 (if that file exists) are used.
86 .BR \-o , " \-\-output " \fIlist\fP
87 Specify which output columns to print. Use
89 to get a list of all supported columns.
91 The default list of columns may be extended if \fIlist\fP is
92 specified in the format \fI+list\fP (e.g., \fB-o +UUID\fP).
94 \fB\-s\fR, \fB\-\-getsz\fR
95 Print the size in 512-byte sectors of each given block device. This option is DEPRECATED
99 \fB\-t\fR, \fB\-\-type\fR \fItype\fR
100 Enable support only for disklabels of the specified \fItype\fP, and disable
101 support for all other types.
103 \fB\-u\fR, \fB\-\-units\fR[=\fIunit\fR]
104 When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The
105 default is to show sizes in sectors. For backward compatibility, it is possible
106 to use the option without the \fIunit\fR argument -- then the default is used.
107 Note that the optional \fIunit\fR argument cannot be separated from the \fB-u\fR
108 option by a space, the correct form is for example '-u=cylinders'.
111 \fB\-C\fR, \fB\-\-cylinders\fR \fInumber\fR
112 Specify the number of cylinders of the disk.
113 I have no idea why anybody would want to do so.
115 \fB\-H\fR, \fB\-\-heads\fR \fInumber\fR
116 Specify the number of heads of the disk. (Not the physical number,
117 of course, but the number used for partition tables.)
118 Reasonable values are 255 and 16.
120 \fB\-S\fR, \fB\-\-sectors\fR \fInumber\fR
121 Specify the number of sectors per track of the disk.
122 (Not the physical number, of course, but the number used for
123 partition tables.) A reasonable value is 63.
126 \fB\-w\fR, \fB\-\-wipe\fR \fIwhen\fR
127 Wipe filesystem, RAID and partition-table signatures from the device, in order
128 to avoid possible collisions. The argument \fIwhen\fR can be \fBauto\fR,
129 \fBnever\fR or \fBalways\fR. When this option is not given, the default is
130 \fBauto\fR, in which case signatures are wiped only when in interactive mode.
131 In all cases detected signatures are reported by warning messages
132 before a new partition table is created. See also
137 \fB\-W\fR, \fB\-\-wipe-partition\fR \fIwhen\fR
138 Wipe filesystem, RAID and partition-table signatures from a newly created
139 partitions, in order to avoid possible collisions. The argument \fIwhen\fR can
140 be \fBauto\fR, \fBnever\fR or \fBalways\fR. When this option is not given, the
141 default is \fBauto\fR, in which case signatures are wiped only when in
142 interactive mode and after confirmation by user. In all cases detected
143 signatures are reported by warning messages before a new partition is
149 \fB\-V\fR, \fB\-\-version\fR
150 Display version information and exit.
155 is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk.
156 Old systems without libata (a library used inside the Linux kernel to support
157 ATA host controllers and devices) make a difference between IDE and SCSI disks.
158 In such cases the device name will be /dev/hd* (IDE) or /dev/sd* (SCSI).
162 is a device name followed by a partition number. For example, /dev/sda1 is the
163 first partition on the first hard disk in the system. See also Linux kernel
164 documentation (the Documentation/devices.txt file).
167 The "last sector" dialog accepts partition size specified by number of sectors
168 or by +/-<size>{K,B,M,G,...} notation.
170 If the size is prefixed by '+' then it is interpreted as relative to the
171 partition first sector. If the size is prefixed by '-' then it is interpreted
172 as relative to the high limit (last available sector for the partition).
174 In the case the size is specified in bytes than the number may be followed by
175 the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on for GiB, TiB,
176 PiB, EiB, ZiB and YiB. The "iB" is optional, e.g., "K" has the same meaning as
179 The relative sizes are always aligned according to device I/O limits. The
180 +/-<size>{K,B,M,G,...} notation is recommended.
182 For backward compatibility fdisk also accepts the suffixes KB=1000,
183 MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N suffixes
188 allows to read (by 'I' command) sfdisk compatible script files. The script is
189 applied to in-memory partition table, and then it is possible to modify the
190 partition table before you write it to the device.
192 And vice-versa it is possible to write the current in-memory disk layout
193 to the script file by command 'O'.
195 The script files are compatible between cfdisk, sfdisk, fdisk and another
196 libfdisk applications. For more details see
200 .B GPT (GUID Partition Table)
202 GPT is modern standard for the layout of the partition table. GPT uses 64-bit
203 logical block addresses, checksums, UUIDs and names for partitions and an
204 unlimited number of partitions (although the number of partitions is
205 usually restricted to 128 in many partitioning tools).
207 Note that the first sector is still reserved for a
209 in the GPT specification. It prevents MBR-only partitioning tools
210 from mis-recognizing and overwriting GPT disks.
212 GPT is always a better choice than MBR, especially on modern hardware with a UEFI
218 A DOS-type partition table can describe an unlimited number of partitions. In sector 0
219 there is room for the description of 4 partitions (called `primary'). One of
220 these may be an extended partition; this is a box holding logical partitions,
221 with descriptors found in a linked list of sectors, each preceding the
222 corresponding logical partitions. The four primary partitions, present or not,
223 get numbers 1-4. Logical partitions are numbered starting from 5.
225 In a DOS-type partition table the starting offset and the size of each
226 partition is stored in two ways: as an absolute number of sectors (given in 32
228 .B Cylinders/Heads/Sectors
229 triple (given in 10+8+6 bits). The former is OK -- with 512-byte sectors this
230 will work up to 2 TB. The latter has two problems. First, these C/H/S fields
231 can be filled only when the number of heads and the number of sectors per track
232 are known. And second, even if we know what these numbers should be, the 24
233 bits that are available do not suffice. DOS uses C/H/S only, Windows uses
234 both, Linux never uses C/H/S. The
235 .B C/H/S addressing is deprecated
236 and may be unsupported in some later fdisk version.
238 .B Please, read the DOS-mode section if you want DOS-compatible partitions.
240 does not care about cylinder boundaries by default.
245 A BSD/Sun disklabel can describe 8 partitions, the third of which should be a `whole
246 disk' partition. Do not start a partition that actually uses its first sector
247 (like a swap partition) at cylinder 0, since that will destroy the disklabel.
250 is usually nested within a DOS partition.
255 An IRIX/SGI disklabel can describe 16 partitions, the eleventh of which should be an entire
256 `volume' partition, while the ninth should be labeled `volume header'. The
257 volume header will also cover the partition table, i.e., it starts at block
258 zero and extends by default over five cylinders. The remaining space in the
259 volume header may be used by header directory entries. No partitions may
260 overlap with the volume header. Also do not change its type or make some
261 filesystem on it, since you will lose the partition table. Use this type of
262 label only when working with Linux on IRIX/SGI machines or IRIX/SGI disks under
266 A sync() and an ioctl(BLKRRPART) (rereading the partition table from disk)
267 are performed before exiting when the partition table has been updated.
269 .SH "DOS mode and DOS 6.x WARNING"
270 .B Note that all this is deprecated. You don't have to care about things like
271 .B geometry and cylinders on modern operating systems. If you really want
272 .B DOS-compatible partitioning then you have to enable DOS mode and cylinder
273 .B units by using the '-c=dos -u=cylinders' fdisk command-line options.
275 The DOS 6.x FORMAT command looks for some information in the first sector of
276 the data area of the partition, and treats this information as more reliable
277 than the information in the partition table. DOS FORMAT expects DOS FDISK to
278 clear the first 512 bytes of the data area of a partition whenever a size
279 change occurs. DOS FORMAT will look at this extra information even if the /U
280 flag is given -- we consider this a bug in DOS FORMAT and DOS FDISK.
282 The bottom line is that if you use \fBfdisk\fR or \fBcfdisk\fR to change the
283 size of a DOS partition table entry, then you must also use
284 .BR dd "(1) to " "zero the first 512 bytes"
285 of that partition before using DOS FORMAT to format the partition. For
286 example, if you were using \fBfdisk\fR to make a DOS partition table entry for
287 /dev/sda1, then (after exiting \fBfdisk\fR and rebooting Linux so that the
288 partition table information is valid) you would use the command "dd
289 if=/dev/zero of=/dev/sda1 bs=512 count=1" to zero the first 512 bytes of the
293 usually obtains the disk geometry automatically. This is not necessarily the
294 physical disk geometry (indeed, modern disks do not really have anything like a
295 physical geometry, certainly not something that can be described in the simplistic
296 Cylinders/Heads/Sectors form), but it is the disk geometry that MS-DOS uses for
299 Usually all goes well by default, and there are no problems if Linux is the
300 only system on the disk. However, if the disk has to be shared with other
301 operating systems, it is often a good idea to let an fdisk from another
302 operating system make at least one partition. When Linux boots it looks at the
303 partition table, and tries to deduce what (fake) geometry is required for good
304 cooperation with other systems.
306 Whenever a partition table is printed out in DOS mode, a consistency check is
307 performed on the partition table entries. This check verifies that the
308 physical and logical start and end points are identical, and that each
309 partition starts and ends on a cylinder boundary (except for the first
312 Some versions of MS-DOS create a first partition which does not begin
313 on a cylinder boundary, but on sector 2 of the first cylinder.
314 Partitions beginning in cylinder 1 cannot begin on a cylinder boundary, but
315 this is unlikely to cause difficulty unless you have OS/2 on your machine.
317 For best results, you should always use an OS-specific partition table
318 program. For example, you should make DOS partitions with the DOS FDISK
319 program and Linux partitions with the Linux fdisk or Linux cfdisk programs.
321 Implicit coloring can be disabled by an empty file \fI/etc/terminal-colors.d/fdisk.disable\fR.
324 .BR terminal-colors.d (5)
325 for more details about colorization configuration. The logical color names
331 The header of the output tables.
334 The help section titles.
337 The warning messages.
352 The original version was written by
353 Andries E. Brouwer, A. V. Le Blanc and others.
357 enables fdisk debug output.
358 .IP LIBFDISK_DEBUG=all
359 enables libfdisk debug output.
360 .IP LIBBLKID_DEBUG=all
361 enables libblkid debug output.
362 .IP LIBSMARTCOLS_DEBUG=all
363 enables libsmartcols debug output.
364 .IP LIBSMARTCOLS_DEBUG_PADDING=on
365 use visible padding characters. Requires enabled LIBSMARTCOLS_DEBUG.
374 The fdisk command is part of the util-linux package and is available from
375 https://www.kernel.org/pub/linux/utils/util-linux/.