1FDISK(8) System Administration FDISK(8)
2
6 fdisk - manipulate disk partition table
7
9 fdisk [options] device
10 fdisk -l [device...]
12
14 fdisk is a dialog-driven program for creation and manipulation of
15 partition tables. It understands GPT, MBR, Sun, SGI and BSD partition
16 tables.
17 Block devices can be divided into one or more logical disks called
19 partitions. This division is recorded in the partition table, usually
20 found in sector 0 of the disk. (In the BSD world one talks about `disk
21 slices' and a `disklabel'.)
22 All partitioning is driven by device I/O limits (the topology) by
24 default. fdisk is able to optimize the disk layout for a 4K-sector size
25 and use an alignment offset on modern devices for MBR and GPT. It is
26 always a good idea to follow fdisk's defaults as the default values
27 (e.g., first and last partition sectors) and partition sizes specified
28 by the +/-<size>{M,G,...} notation are always aligned according to the
29 device properties.
30 CHS (Cylinder-Head-Sector) addressing is deprecated and not used by
32 default. Please, do not follow old articles and recommendations with
33 fdisk -S <n> -H <n> advices for SSD or 4K-sector devices.
34 Note that partx(8) provides a rich interface for scripts to print disk
36 layouts, fdisk is mostly designed for humans. Backward compatibility in
37 the output of fdisk is not guaranteed. The input (the commands) should
38 always be backward compatible.
39
41 -b, --sector-size sectorsize
42 Specify the sector size of the disk. Valid values are 512, 1024,
43 2048, and 4096. (Recent kernels know the sector size. Use this
44 option only on old kernels or to override the kernel’s ideas.)
45 Since util-linux-2.17, fdisk differentiates between logical and
46 physical sector size. This option changes both sector sizes to
47 sectorsize.
48 -B, --protect-boot
50 Don’t erase the beginning of the first disk sector when creating a
51 new disk label. This feature is supported for GPT and MBR.
52 -c, --compatibility[=mode]
54 Specify the compatibility mode, 'dos' or 'nondos'. The default is
55 non-DOS mode. For backward compatibility, it is possible to use the
56 option without the mode argument — then the default is used. Note
57 that the optional mode argument cannot be separated from the -c
58 option by a space, the correct form is for example -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, never
65 or always. If the when argument is omitted, it defaults to auto.
66 The colors can be disabled; for the current built-in default see
67 the --help output. See also the COLORS section.
68 -l, --list
70 List the partition tables for the specified devices and then exit.
71 If no devices are given, the devices mentioned in /proc/partitions
73 (if this file exists) are used. Devices are always listed in the
74 order in which they are specified on the command-line, or by the
75 kernel listed in /proc/partitions.
76 -x, --list-details
78 Like --list, but provides more details.
79 --lock[=mode]
81 Use exclusive BSD lock for device or file it operates. The optional
82 argument mode can be yes, no (or 1 and 0) or nonblock. If the mode
83 argument is omitted, it defaults to "yes". This option overwrites
84 environment variable $LOCK_BLOCK_DEVICE. The default is not to use
85 any lock at all, but it’s recommended to avoid collisions with
86 udevd or other tools.
87 -n, --noauto-pt
89 Don’t automatically create a default partition table on empty
90 device. The partition table has to be explicitly created by user
91 (by command like 'o', 'g', etc.).
92 -o, --output list
94 Specify which output columns to print. Use --help to get a list of
95 all supported columns.
96 The default list of columns may be extended if list is specified in
98 the format +list (e.g., -o +UUID).
99 -s, --getsz
101 Print the size in 512-byte sectors of each given block device. This
102 option is DEPRECATED in favour of blockdev(8).
103 -t, --type type
105 Enable support only for disklabels of the specified type, and
106 disable support for all other types.
107 -u, --units[=unit]
109 When listing partition tables, show sizes in 'sectors' or in
110 'cylinders'. The default is to show sizes in sectors. For backward
111 compatibility, it is possible to use the option without the unit
112 argument — then the default is used. Note that the optional unit
113 argument cannot be separated from the -u option by a space, the
114 correct form is for example '*-u=*cylinders'.
115 -C, --cylinders number
117 Specify the number of cylinders of the disk. I have no idea why
118 anybody would want to do so.
119 -H, --heads number
121 Specify the number of heads of the disk. (Not the physical number,
122 of course, but the number used for partition tables.) Reasonable
123 values are 255 and 16.
124 -S, --sectors number
126 Specify the number of sectors per track of the disk. (Not the
127 physical number, of course, but the number used for partition
128 tables.) A reasonable value is 63.
129 -w, --wipe when
131 Wipe filesystem, RAID and partition-table signatures from the
132 device, in order to avoid possible collisions. The argument when
133 can be auto, never or always. When this option is not given, the
134 default is auto, in which case signatures are wiped only when in
135 interactive mode. In all cases detected signatures are reported by
136 warning messages before a new partition table is created. See also
137 wipefs(8) command.
138 -W, --wipe-partitions when
140 Wipe filesystem, RAID and partition-table signatures from a newly
141 created partitions, in order to avoid possible collisions. The
142 argument when can be auto, never or always. When this option is not
143 given, the default is auto, in which case signatures are wiped only
144 when in interactive mode and after confirmation by user. In all
145 cases detected signatures are reported by warning messages before a
146 new partition is created. See also wipefs(8) command.
147 -V, --version
149 Display version information and exit.
150
152 The device is usually /dev/sda, /dev/sdb or so. A device name refers to
153 the entire disk. Old systems without libata (a library used inside the
154 Linux kernel to support ATA host controllers and devices) make a
155 difference between IDE and SCSI disks. In such cases the device name
156 will be /dev/hd* (IDE) or /dev/sd* (SCSI).
157 The partition is a device name followed by a partition number. For
159 example, /dev/sda1 is the first partition on the first hard disk in the
160 system. See also Linux kernel documentation (the
161 Documentation/admin-guide/devices.txt file).
162
164 The "last sector" dialog accepts partition size specified by number of
165 sectors or by +/-<size>{K,B,M,G,...} notation.
166 If the size is prefixed by '+' then it is interpreted as relative to
168 the partition first sector. If the size is prefixed by '-' then it is
169 interpreted as relative to the high limit (last available sector for
170 the partition).
171 In the case the size is specified in bytes than the number may be
173 followed by the multiplicative suffixes KiB=1024, MiB=1024*1024, and so
174 on for GiB, TiB, PiB, EiB, ZiB and YiB. The "iB" is optional, e.g., "K"
175 has the same meaning as "KiB".
176 The relative sizes are always aligned according to device I/O limits.
178 The +/-<size>{K,B,M,G,...} notation is recommended.
179 For backward compatibility fdisk also accepts the suffixes KB=1000,
181 MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N
182 suffixes are deprecated.
183
185 fdisk allows reading (by 'I' command) sfdisk(8) compatible script
186 files. The script is applied to in-memory partition table, and then it
187 is possible to modify the partition table before you write it to the
188 device.
189 And vice-versa it is possible to write the current in-memory disk
191 layout to the script file by command 'O'.
192 The script files are compatible between cfdisk(8), sfdisk(8), fdisk and
194 other libfdisk applications. For more details see sfdisk(8).
195
197 GPT (GUID Partition Table)
198 GPT is modern standard for the layout of the partition table. GPT
199 uses 64-bit logical block addresses, checksums, UUIDs and names for
200 partitions and an unlimited number of partitions (although the
201 number of partitions is usually restricted to 128 in many
202 partitioning tools).
203 Note that the first sector is still reserved for a protective MBR
205 in the GPT specification. It prevents MBR-only partitioning tools
206 from mis-recognizing and overwriting GPT disks.
207 GPT is always a better choice than MBR, especially on modern
209 hardware with a UEFI boot loader.
210 DOS-type (MBR)
212 A DOS-type partition table can describe an unlimited number of
213 partitions. In sector 0 there is room for the description of 4
214 partitions (called `primary'). One of these may be an extended
215 partition; this is a box holding logical partitions, with
216 descriptors found in a linked list of sectors, each preceding the
217 corresponding logical partitions. The four primary partitions,
218 present or not, get numbers 1-4. Logical partitions are numbered
219 starting from 5.
220 In a DOS-type partition table the starting offset and the size of
222 each partition is stored in two ways: as an absolute number of
223 sectors (given in 32 bits), and as a Cylinders/Heads/Sectors triple
224 (given in 10+8+6 bits). The former is OK — with 512-byte sectors
225 this will work up to 2 TB. The latter has two problems. First,
226 these C/H/S fields can be filled only when the number of heads and
227 the number of sectors per track are known. And second, even if we
228 know what these numbers should be, the 24 bits that are available
229 do not suffice. DOS uses C/H/S only, Windows uses both, Linux never
230 uses C/H/S. The C/H/S addressing is deprecated and may be
231 unsupported in some later fdisk version.
232 Please, read the DOS-mode section if you want DOS-compatible
234 partitions. fdisk does not care about cylinder boundaries by
235 default.
236 BSD/Sun-type
238 A BSD/Sun disklabel can describe 8 partitions, the third of which
239 should be a `whole disk' partition. Do not start a partition that
240 actually uses its first sector (like a swap partition) at cylinder
241 0, since that will destroy the disklabel. Note that a BSD label is
242 usually nested within a DOS partition.
243 IRIX/SGI-type
245 An IRIX/SGI disklabel can describe 16 partitions, the eleventh of
246 which should be an entire `volume' partition, while the ninth
247 should be labeled `volume header'. The volume header will also
248 cover the partition table, i.e., it starts at block zero and
249 extends by default over five cylinders. The remaining space in the
250 volume header may be used by header directory entries. No
251 partitions may overlap with the volume header. Also do not change
252 its type or make some filesystem on it, since you will lose the
253 partition table. Use this type of label only when working with
254 Linux on IRIX/SGI machines or IRIX/SGI disks under Linux.
255 A sync() and an ioctl(BLKRRPART) (rereading the partition table
257 from disk) are performed before exiting when the partition table
258 has been updated.
259
261 Note that all this is deprecated. You don’t have to care about things
262 like geometry and cylinders on modern operating systems. If you really
263 want DOS-compatible partitioning then you have to enable DOS mode and
264 cylinder units by using the '-c=dos -u=cylinders' fdisk command-line
265 options.
266 The DOS 6.x FORMAT command looks for some information in the first
268 sector of the data area of the partition, and treats this information
269 as more reliable than the information in the partition table. DOS
270 FORMAT expects DOS FDISK to clear the first 512 bytes of the data area
271 of a partition whenever a size change occurs. DOS FORMAT will look at
272 this extra information even if the /U flag is given — we consider this
273 a bug in DOS FORMAT and DOS FDISK.
274 The bottom line is that if you use fdisk or cfdisk to change the size
276 of a DOS partition table entry, then you must also use dd(1) to zero
277 the first 512 bytes of that partition before using DOS FORMAT to format
278 the partition. For example, if you were using fdisk to make a DOS
279 partition table entry for /dev/sda1, then (after exiting fdisk and
280 rebooting Linux so that the partition table information is valid) you
281 would use the command dd if=/dev/zero of=/dev/sda1 bs=512 count=1 to
282 zero the first 512 bytes of the partition.
283 fdisk usually obtains the disk geometry automatically. This is not
285 necessarily the physical disk geometry (indeed, modern disks do not
286 really have anything like a physical geometry, certainly not something
287 that can be described in the simplistic Cylinders/Heads/Sectors form),
288 but it is the disk geometry that MS-DOS uses for the partition table.
289 Usually all goes well by default, and there are no problems if Linux is
291 the only system on the disk. However, if the disk has to be shared with
292 other operating systems, it is often a good idea to let an fdisk from
293 another operating system make at least one partition. When Linux boots
294 it looks at the partition table, and tries to deduce what (fake)
295 geometry is required for good cooperation with other systems.
296 Whenever a partition table is printed out in DOS mode, a consistency
298 check is performed on the partition table entries. This check verifies
299 that the physical and logical start and end points are identical, and
300 that each partition starts and ends on a cylinder boundary (except for
301 the first partition).
302 Some versions of MS-DOS create a first partition which does not begin
304 on a cylinder boundary, but on sector 2 of the first cylinder.
305 Partitions beginning in cylinder 1 cannot begin on a cylinder boundary,
306 but this is unlikely to cause difficulty unless you have OS/2 on your
307 machine.
308 For best results, you should always use an OS-specific partition table
310 program. For example, you should make DOS partitions with the DOS FDISK
311 program and Linux partitions with the Linux fdisk or Linux cfdisk(8)
312 programs.
313
315 Implicit coloring can be disabled by an empty file
316 /etc/terminal-colors.d/fdisk.disable.
317 See terminal-colors.d(5) for more details about colorization
319 configuration. The logical color names supported by fdisk are:
320 header
322 The header of the output tables.
323 help-title
325 The help section titles.
326 warn
328 The warning messages.
329 welcome
331 The welcome message.
332
334 FDISK_DEBUG=all
335 enables fdisk debug output.
336 LIBFDISK_DEBUG=all
338 enables libfdisk debug output.
339 LIBBLKID_DEBUG=all
341 enables libblkid debug output.
342 LIBSMARTCOLS_DEBUG=all
344 enables libsmartcols debug output.
345 LIBSMARTCOLS_DEBUG_PADDING=on
347 use visible padding characters.
348 LOCK_BLOCK_DEVICE=<mode>
350 use exclusive BSD lock. The mode is "1" or "0". See --lock for more
351 details.
352
354 Karel Zak <kzak@redhat.com>, Davidlohr Bueso <dave@gnu.org>
355 The original version was written by Andries E. Brouwer, A. V. Le Blanc
357 and others.
358
360 cfdisk(8), mkfs(8), partx(8), sfdisk(8)
361
363 For bug reports, use the issue tracker at
364 https://github.com/karelzak/util-linux/issues.
365
367 The fdisk command is part of the util-linux package which can be
368 downloaded from Linux Kernel Archive
369 <https://www.kernel.org/pub/linux/utils/util-linux/>.
370util-linux 2.37.2 2021-08-16 FDISK(8)