1FDISK(8) System Administration FDISK(8)
2
6 fdisk - manipulate disk partition table
7
10 fdisk [options] device
11 fdisk -l [device...]
13
16 fdisk is a dialog-driven program for creation and manipulation of par‐
17 tition tables. It understands GPT, MBR, Sun, SGI and BSD partition
18 tables.
19 Block devices can be divided into one or more logical disks called par‐
21 titions. This division is recorded in the partition table, usually
22 found in sector 0 of the disk. (In the BSD world one talks about `disk
23 slices' and a `disklabel'.)
24 All partitioning is driven by device I/O limits (the topology) by
26 default. fdisk is able to optimize the disk layout for a 4K-sector
27 size and use an alignment offset on modern devices for MBR and GPT. It
28 is always a good idea to follow fdisk's defaults as the default values
29 (e.g. first and last partition sectors) and partition sizes specified
30 by the +<size>{M,G,...} notation are always aligned according to the
31 device properties.
32 Note that partx(8) provides a rich interface for scripts to print disk
34 layouts, fdisk is mostly designed for humans. Backward compatibility
35 in the output of fdisk is not guaranteed. The input (the commands)
36 should always be backward compatible.
37
40 -b, --sector-size sectorsize
41 Specify the sector size of the disk. Valid values are 512,
42 1024, 2048, and 4096. (Recent kernels know the sector size.
43 Use this option only on old kernels or to override the kernel's
44 ideas.) Since util-linux-2.17, fdisk differentiates between
45 logical and physical sector size. This option changes both sec‐
46 tor sizes to sectorsize.
47 -B, --protect-boot
49 Don't erase the begin of the first disk sector when create a new
50 disk label. This feature is supported for GPT and MBR.
51 -c, --compatibility[=mode]
53 Specify the compatibility mode, 'dos' or 'nondos'. The default
54 is non-DOS mode. For backward compatibility, it is possible to
55 use the option without the mode argument -- then the default is
56 used. Note that the optional mode argument cannot be separated
57 from the -c option by a space, the correct form is for example
58 '-c=dos'.
59 -h, --help
61 Display a help text and exit.
62 -L, --color[=when]
64 Colorize the output. The optional argument when can be auto,
65 never or always. If the when argument is omitted, it defaults
66 to auto. The colors can be disabled; for the current built-in
67 default see the --help output. See also the COLORS section.
68 -l, --list
70 List the partition tables for the specified devices and then
71 exit. If no devices are given, those mentioned in /proc/parti‐
72 tions (if that file exists) are used.
73 -o, --output list
75 Specify which output columns to print. Use --help to get a list
76 of all supported columns.
77 The default list of columns may be extended if list is specified
79 in the format +list (e.g. -o +UUID).
80 -s, --getsz
82 Print the size in 512-byte sectors of each given block device.
83 This option is DEPRECATED in favour of blockdev(1).
84 -t, --type type
86 Enable support only for disklabels of the specified type, and
87 disable support for all other types.
88 -u, --units[=unit]
90 When listing partition tables, show sizes in 'sectors' or in
91 'cylinders'. The default is to show sizes in sectors. For
92 backward compatibility, it is possible to use the option without
93 the unit argument -- then the default is used. Note that the
94 optional unit argument cannot be separated from the -u option by
95 a space, the correct form is for example '-u=cylinders'.
96 -C, --cylinders number
99 Specify the number of cylinders of the disk. I have no idea why
100 anybody would want to do so.
101 -H, --heads number
103 Specify the number of heads of the disk. (Not the physical num‐
104 ber, of course, but the number used for partition tables.) Rea‐
105 sonable values are 255 and 16.
106 -S, --sectors number
108 Specify the number of sectors per track of the disk. (Not the
109 physical number, of course, but the number used for partition
110 tables.) A reasonable value is 63.
111 -w, --wipe when
114 Wipe filesystem, RAID and partition-table signatures from the
115 device, in order to avoid possible collisions. The argument
116 when can be auto, never or always. When this option is not
117 given, the default is auto, in which case signatures are wiped
118 only when in interactive mode. In all cases detected signatures
119 are reported by warning messages before a new partition table is
120 created. See also wipefs(8) command.
121 -W, --wipe-partition when
124 Wipe filesystem, RAID and partition-table signatures from a
125 newly created partitions, in order to avoid possible collisions.
126 The argument when can be auto, never or always. When this
127 option is not given, the default is auto, in which case signa‐
128 tures are wiped only when in interactive mode and after confir‐
129 mation by user. In all cases detected signatures are reported
130 by warning messages before a new partition is created. See also
131 wipefs(8) command.
132 -V, --version
135 Display version information and exit.
136
139 The device is usually /dev/sda, /dev/sdb or so. A device name refers
140 to the entire disk. Old systems without libata (a library used inside
141 the Linux kernel to support ATA host controllers and devices) make a
142 difference between IDE and SCSI disks. In such cases the device name
143 will be /dev/hd* (IDE) or /dev/sd* (SCSI).
144 The partition is a device name followed by a partition number. For
146 example, /dev/sda1 is the first partition on the first hard disk in the
147 system. See also Linux kernel documentation (the Documenta‐
148 tion/devices.txt file).
149
152 The "last sector" dialog accepts partition size specified by number of
153 sectors or by +<size>{K,B,M,G,...} notation.
154 If the size is prefixed by '+' then it is interpreted as relative to
156 the partition first sector. In this case the size is expected in bytes
157 and the number may be followed by the multiplicative suffixes KiB=1024,
158 MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB. The "iB"
159 is optional, e.g. "K" has the same meaning as "KiB".
160 The relative sizes are always aligned according to device I/O limits.
162 The +<size>{K,B,M,G,...} notation is recommended.
163 For backward compatibility fdisk also accepts the suffixes KB=1000,
165 MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N suf‐
166 fixes are deprecated.
167
170 fdisk allows to read (by 'I' command) sfdisk compatible script files.
171 The script is applied to in-memory partition table, and then it is pos‐
172 sible to modify the partition table before you write it to the device.
173 And vice-versa it is possible to write the current in-memory disk lay‐
175 out to the script file by command 'O'.
176 The script files are compatible between cfdisk, sfdisk, fdisk and
178 another libfdisk applications. For more details see sfdisk(8).
179
182 GPT (GUID Partition Table)
183 GPT is modern standard for the layout of the partition table.
184 GPT uses 64-bit logical block addresses, checksums, UUIDs and
185 names for partitions and an unlimited number of partitions
186 (although the number of partitions is usually restricted to 128
187 in many partitioning tools).
188 Note that the first sector is still reserved for a protective
190 MBR in the GPT specification. It prevents MBR-only partitioning
191 tools from mis-recognizing and overwriting GPT disks.
192 GPT is always a better choice than MBR, especially on modern
194 hardware with a UEFI boot loader.
195 DOS-type (MBR)
197 A DOS-type partition table can describe an unlimited number of
198 partitions. In sector 0 there is room for the description of 4
199 partitions (called `primary'). One of these may be an extended
200 partition; this is a box holding logical partitions, with
201 descriptors found in a linked list of sectors, each preceding
202 the corresponding logical partitions. The four primary parti‐
203 tions, present or not, get numbers 1-4. Logical partitions are
204 numbered starting from 5.
205 In a DOS-type partition table the starting offset and the size
207 of each partition is stored in two ways: as an absolute number
208 of sectors (given in 32 bits), and as a Cylinders/Heads/Sectors
209 triple (given in 10+8+6 bits). The former is OK -- with
210 512-byte sectors this will work up to 2 TB. The latter has two
211 problems. First, these C/H/S fields can be filled only when the
212 number of heads and the number of sectors per track are known.
213 And second, even if we know what these numbers should be, the 24
214 bits that are available do not suffice. DOS uses C/H/S only,
215 Windows uses both, Linux never uses C/H/S. The C/H/S addressing
216 is deprecated and may be unsupported in some later fdisk ver‐
217 sion.
218 Please, read the DOS-mode section if you want DOS-compatible
220 partitions. fdisk does not care about cylinder boundaries by
221 default.
222 BSD/Sun-type
224 A BSD/Sun disklabel can describe 8 partitions, the third of
225 which should be a `whole disk' partition. Do not start a parti‐
226 tion that actually uses its first sector (like a swap partition)
227 at cylinder 0, since that will destroy the disklabel. Note that
228 a BSD label is usually nested within a DOS partition.
229 IRIX/SGI-type
231 An IRIX/SGI disklabel can describe 16 partitions, the eleventh
232 of which should be an entire `volume' partition, while the ninth
233 should be labeled `volume header'. The volume header will also
234 cover the partition table, i.e., it starts at block zero and
235 extends by default over five cylinders. The remaining space in
236 the volume header may be used by header directory entries. No
237 partitions may overlap with the volume header. Also do not
238 change its type or make some filesystem on it, since you will
239 lose the partition table. Use this type of label only when
240 working with Linux on IRIX/SGI machines or IRIX/SGI disks under
241 Linux.
242 A sync() and an ioctl(BLKRRPART) (rereading the partition table from
244 disk) are performed before exiting when the partition table has been
245 updated.
246
249 Note that all this is deprecated. You don't have to care about things
250 like geometry and cylinders on modern operating systems. If you really
251 want DOS-compatible partitioning then you have to enable DOS mode and
252 cylinder units by using the '-c=dos -u=cylinders' fdisk command-line
253 options.
254 The DOS 6.x FORMAT command looks for some information in the first sec‐
256 tor of the data area of the partition, and treats this information as
257 more reliable than the information in the partition table. DOS FORMAT
258 expects DOS FDISK to clear the first 512 bytes of the data area of a
259 partition whenever a size change occurs. DOS FORMAT will look at this
260 extra information even if the /U flag is given -- we consider this a
261 bug in DOS FORMAT and DOS FDISK.
262 The bottom line is that if you use fdisk or cfdisk to change the size
264 of a DOS partition table entry, then you must also use dd(1) to zero
265 the first 512 bytes of that partition before using DOS FORMAT to format
266 the partition. For example, if you were using fdisk to make a DOS par‐
267 tition table entry for /dev/sda1, then (after exiting fdisk and reboot‐
268 ing Linux so that the partition table information is valid) you would
269 use the command "dd if=/dev/zero of=/dev/sda1 bs=512 count=1" to zero
270 the first 512 bytes of the partition.
271 fdisk usually obtains the disk geometry automatically. This is not
273 necessarily the physical disk geometry (indeed, modern disks do not
274 really have anything like a physical geometry, certainly not something
275 that can be described in the simplistic Cylinders/Heads/Sectors form),
276 but it is the disk geometry that MS-DOS uses for the partition table.
277 Usually all goes well by default, and there are no problems if Linux is
279 the only system on the disk. However, if the disk has to be shared
280 with other operating systems, it is often a good idea to let an fdisk
281 from another operating system make at least one partition. When Linux
282 boots it looks at the partition table, and tries to deduce what (fake)
283 geometry is required for good cooperation with other systems.
284 Whenever a partition table is printed out in DOS mode, a consistency
286 check is performed on the partition table entries. This check verifies
287 that the physical and logical start and end points are identical, and
288 that each partition starts and ends on a cylinder boundary (except for
289 the first partition).
290 Some versions of MS-DOS create a first partition which does not begin
292 on a cylinder boundary, but on sector 2 of the first cylinder. Parti‐
293 tions beginning in cylinder 1 cannot begin on a cylinder boundary, but
294 this is unlikely to cause difficulty unless you have OS/2 on your
295 machine.
296 For best results, you should always use an OS-specific partition table
298 program. For example, you should make DOS partitions with the DOS
299 FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk
300 programs.
301
303 Implicit coloring can be disabled by an empty file /etc/terminal-col‐
304 ors.d/fdisk.disable.
305 See terminal-colors.d(5) for more details about colorization configura‐
307 tion. The logical color names supported by fdisk are:
308 header The header of the output tables.
310 help-title
312 The help section titles.
313 warn The warning messages.
315 welcome
317 The welcome message.
318
321 Karel Zak ⟨kzak@redhat.com⟩
322 Davidlohr Bueso ⟨dave@gnu.org⟩
323 The original version was written by Andries E. Brouwer, A. V. Le Blanc
325 and others.
326
329 FDISK_DEBUG=all
330 enables fdisk debug output.
331 LIBFDISK_DEBUG=all
333 enables libfdisk debug output.
334 LIBBLKID_DEBUG=all
336 enables libblkid debug output.
337 LIBSMARTCOLS_DEBUG=all
339 enables libsmartcols debug output.
340 LIBSMARTCOLS_DEBUG_PADDING=on
342 use visible padding characters. Requires enabled LIBSMART‐
343 COLS_DEBUG.
344
347 cfdisk(8), mkfs(8), partx(8), sfdisk(8)
348
351 The fdisk command is part of the util-linux package and is available
352 from https://www.kernel.org/pub/linux/utils/util-linux/.
353util-linux February 2016 FDISK(8)