Linux sfdisk 命令
NAME
sfdisk - partition table manipulator for LinuxSYNOPSIS（sfdisk用法格式简要）
sfdisk [options] device
sfdisk -s [partition]
DESCRIPTION
sfdisk has four (main) uses: list the size of a partition, list the partitions on a device, check the partitions on a device, and very dangerous repartition a device. （sfdisk 有四种用法）sfdisk doesn't understand the GUID Partition Table (GPT) format and it is not designed for large partitions. In these cases use the more advanced GNU parted(8).
sfdisk四种用法：
List sizes （列举大小）
sfdisk -s partition gives the size of partition in blocks. This may be useful in connection with programs like mkswap(8). Here partition is usually something like /dev/hda1 or /dev/sdb12, but may also be an entire disk, like /dev/xda.
% sfdisk -s /dev/hda9
81599
If the partition argument is omitted, sfdisk will list the sizes of all disks, and the total:
% sfdisk -s
/dev/hda: 208896
/dev/hdb: 1025136
/dev/hdc: 1031063
/dev/sda: 8877895
/dev/sdb: 1758927
total: 12901917 blocks
List partitions（列举分区）
The second type of invocation: sfdisk -l device will list the partitions on the specified device. If the device argument is omitted, the partitions on all hard disks are listed.% sfdisk -l /dev/hdc
Disk /dev/hdc: 16 heads, 63 sectors, 2045 cylinders
Units = cylinders of 516096 bytes, blocks of 1024 bytes, counting from 0
Device Boot Start End #cyls #blocks Id System
/dev/hdc1 0+ 406 407- 205096+ 83 Linux native
/dev/hdc2 407 813 407 205128 83 Linux native
/dev/hdc3 814 2044 1231 620424 83 Linux native
/dev/hdc4 0 - 0 0 0 Empty
The trailing - and + signs indicate that rounding has taken place, and that the actual value is slightly less or more. To see the exact values, ask for a listing with sectors as unit (-u S) .
数据尾部带上（- 和 + ）表示取舍后的值比实际值略小后略大， 为查看实际值可以用下面命令
wiwa@tech:~$ sudo sfdisk -l -u S /dev/sdb
Check partitions（检查分区）
The third type of invocation: sfdisk -V device will apply various consistency checks to the partition tables on device. It prints `OK' or complains. The -V option can be used together with -l. In a shell script one might use sfdisk -V -q device which only returns a status.
wiwa@tech:~$ sudo sfdisk -V /dev/sdb
Create partitions（创建分区）
The fourth type of invocation: sfdisk device will cause sfdisk to read the specification for the desired partitioning of device from standard input, and then to change the partition tables on that disk. Thus it is possible to use sfdisk from a shell script. When sfdisk determines that its standard input is a terminal, it will be conversational; otherwise it will abort on any error.BE EXTREMELY CAREFUL - ONE TYPING MISTAKE AND ALL YOUR DATA IS LOST
As a precaution, one can save the sectors changed by sfdisk:
% sfdisk /dev/hdd -O hdd-partition-sectors.save
...
Then, if you discover that you did something stupid before anything else has been written to disk, it may be possible to recover the old situation with:
% sfdisk /dev/hdd -I hdd-partition-sectors.save
(This is not the same as saving the old partition table: a readable version of the old partition table can be saved using the -d option. However, if you create logical partitions, the sectors describing them are located somewhere on disk, possibly on sectors that were not part of the partition table before. Thus, the information the -O option saves is not a binary version of the output of -d.)
There are many options.
OPTIONS（sfdisk命令选项）
-v, --versionPrint version number of sfdisk and exit immediately.
-h, --help
Print a usage message and exit immediately.
-T, --list-types
Print the recognized types (system Id's).
-s, --show-size
List the size of a partition.
-g, --show-geometry
List the kernel's idea of the geometry of the indicated disk(s).
-G, --show-pt-geometry
List the geometry of the indicated disks guessed by looking at the partition table.
-l, --list
List the partitions of a device.
-d, --dump
Dump the partitions of a device in a format that is usable as input to /fBsfdisk/fR. For example,
% sfdisk -d /dev/hda > hda.out
% sfdisk /dev/hda < hda.out
will correct the bad last extended partition that the OS/2 fdisk creates.
-V, --verify
Test whether partitions seem correct. (See the third invocation type above.)
-i, --increment
Number cylinders etc. starting from 1 instead of 0.
-N number
Change only the single partition indicated. For example:
% sfdisk /dev/hdb -N5
,,,*
will make the fifth partition on /dev/hdb bootable (`active') and change nothing else. (Probably this fifth partition is called /dev/hdb5, but you are free to call it something else, like `/my_equipment/disks/2/5' or so).
-A, --activate number
Make the indicated partition(s) active, and all others inactive.
-c, --id number [Id]
If no Id argument given: print the partition Id of the indicated partition. If an Id argument is present: change the type (Id) of the indicated partition to the given value. This option has two longer forms, --print-id and --change-id. For example:
% sfdisk --print-id /dev/hdb 5
6
% sfdisk --change-id /dev/hdb 5 83
OK
first reports that /dev/hdb5 has Id 6, and then changes that into 83.
-u, --unit letter
Interpret the input and show the output in the units specified by letter. This letter can be one of S, C, B or M, meaning Sectors, Cylinders, Blocks and Megabytes, respectively. The default is cylinders, at least when the geometry is known.
-x, --show-extended
Also list non-primary extended partitions on output, and expect descriptors for them on input.
-C, --cylinders cylinders
Specify the number of cylinders, possibly overriding what the kernel thinks.
-H, --heads heads
Specify the number of heads, possibly overriding what the kernel thinks.
-S, --sectors sectors
Specify the number of sectors, possibly overriding what the kernel thinks.
-f, --force
Do what I say, even if it is stupid.
-q, --quiet
Suppress warning messages.
-L, --Linux
Do not complain about things irrelevant for Linux.
-D, --DOS
For DOS-compatibility: waste a little space. (More precisely: if a partition cannot contain sector 0, e.g. because that is the MBR of the device, or contains the partition table of an extended partition, then sfdisk would make it start the next sector. However, when this option is given it skips to the start of the next track, wasting for example 33 sectors (in case of 34 sectors/track), just like certain versions of DOS do.) Certain Disk Managers and boot loaders (such as OSBS, but not LILO or the OS/2 Boot Manager) also live in this empty space, so maybe you want this option if you use one.
-E, --DOS-extended
Take the starting sector numbers of "inner" extended partitions to be relative to the starting cylinder boundary of the outer one (like some versions of DOS do), rather than relative to the actual starting sector (like Linux does). (The fact that there is a difference here means that one should always let extended partitions start at cylinder boundaries if DOS and Linux should interpret the partition table in the same way. Of course one can only know where cylinder boundaries are when one knows what geometry DOS will use for this disk.)
--IBM, --leave-last
Certain IBM diagnostic programs assume that they can use the last cylinder on a disk for disk-testing purposes. If you think you might ever run such programs, use this option to tell sfdisk that it should not allocate the last cylinder. Sometimes the last cylinder contains a bad sector table.
-n Go through all the motions, but do not actually write to disk.
-R, --re-read
Only execute the BLKRRPART ioctl (to make the kernel re-read the partition table). This can be useful for checking in advance that the final BLKRRPART will be successful, and also when you changed the partition table `by hand' (e.g., using dd from a backup). If the kernel complains (`device busy for revalidation (usage = 2)') then something still uses the device, and you still have to unmount some file system, or say swapoff to some swap partition.
--no-reread
When starting a repartitioning of a disk, sfdisk checks that this disk is not mounted, or in use as a swap device, and refuses to continue if it is. This option suppresses the test. (On the other hand, the -f option would force sfdisk to continue even when this test fails.)
--in-order
Caution, see warning section. To be documented.
--not-in-order
Caution, see warning section. To be documented.
--inside-outer
Caution, see warning section. Chaining order.
--not-inside-outer
Caution, see warning section. Chaining order.
--nested
Caution, see warning section. Every partition is contained in the surrounding partitions and is disjoint from all others.
--chained
Caution, see warning section. Every data partition is contained in the surrounding partitions and disjoint from all others, but extended partitions may lie outside (insofar as allowed by all_logicals_inside_outermost_extended).
--onesector
Caution, see warning section. All data partitions are mutually disjoint; extended partitions each use one sector only (except perhaps for the outermost one).
-O file
Just before writing the new partition, output the sectors that are going to be overwritten to file (where hopefully file resides on another disk, or on a floppy).
-I file
After destroying your filesystems with an unfortunate sfdisk command, you would have been able to restore the old situation if only you had preserved it using the -O flag.
THEORY（disk分区理论）
Block 0 of a disk (the Master Boot Record) contains among other things four partition descriptors. The partitions described here are called primary partitions.A partition descriptor has 6 fields:
struct partition {
unsigned char bootable; /* 0 or 0x80 ， 1btye */
hsc begin_hsc; /* 3 bytes hsc 即 head sector cylinder*/
unsigned char id; /* 1byte*/hsc end_hsc; /* 3bytes*/
unsigned int starting_sector; /* 4bytes*/
unsigned int nr_of_sectors; /* 4btyes*/
}
下面是linux分区结构体的声明格式：
68 struct partition {
69 unsigned char boot_ind; /* 0x80 - active */
70 unsigned char head; /* starting head */
71 unsigned char sector; /* starting sector */
72 unsigned char cyl; /* starting cylinder */
73 unsigned char sys_ind; /* What partition type */
74 unsigned char end_head; /* end head */
75 unsigned char end_sector; /* end sector */
76 unsigned char end_cyl; /* end cylinder */
77 __le32 start_sect; /* starting sector counting from 0 */
78 __le32 nr_sects; /* nr of sectors in partition */
79 } __attribute__((packed));
The two hsc fields indicate head, sector and cylinder of the begin and the end of the partition. Since each hsc field only takes 3 bytes, only 24 bits are available, which does not suffice for big disks (say > 8GB). In fact, due to the wasteful representation (that uses a byte for the number of heads, which is typically 16), problems already start with 0.5GB. However Linux does not use these fields, and problems can arise only at boot time, before Linux has been started. For more details, see the lilo documentation.
Each partition has a type, its `Id', and if this type is 5 or f (`extended partition') the starting sector of the partition again contains 4 partition descriptors. MSDOS only uses the first two of these: the first one an actual data partition, and the second one again an extended partition (or empty). In this way one gets a chain of extended partitions. Other operating systems have slightly different conventions. Linux also accepts type 85 as equivalent to 5 and f - this can be useful if one wants to have extended partitions under Linux past the 1024 cylinder boundary, without DOS FDISK hanging. (If there is no good reason, you should just use 5, which is understood by other systems.)
Partitions that are not primary or extended are called logical. Often, one cannot boot from logical partitions (because the process of finding them is more involved than just looking at the MBR). Note that of an extended partition only the Id and the start are used. There are various conventions about what to write in the other fields. One should not try to use extended partitions for data storage or swap.
INPUT FORMAT（sfdisk输入格式）
sfdisk reads lines of the form
where each line fills one partition descriptor.
Fields are separated by whitespace, or comma or semicolon possibly followed by whitespace; initial and trailing whitespace is ignored. Numbers can be octal, decimal or hexadecimal, decimal is default. When a field is absent or empty, a default value is used.
The
Bootable is specified as [*|-], with as default not-bootable. (The value of this field is irrelevant for Linux - when Linux runs it has been booted already - but might play a role for certain boot loaders and for other operating systems. For example, when there are several primary DOS partitions, DOS assigns C: to the first among these that is bootable.)
Id is given in hex, without the 0x prefix, or is [E|S|L|X], where L (LINUX_NATIVE (83)) is the default, S is LINUX_SWAP (82), E is EXTENDED_PARTITION (5), and X is LINUX_EXTENDED (85).
id 块的值有[ E|S|L|X] 四种格式， E:（EXTENDED _PARTITION）扩展分区， S（LINUX_SWAP）linux转化分区， L（LINUX_NATIVE)linux 原始分区，
The default value of start is the first nonassigned sector/cylinder/...
The default value of size is as much as possible (until next partition or end-of-disk).
However, for the four partitions inside an extended partition, the defaults are: Linux partition, Extended partition, Empty, Empty.
But when the -N option (change a single partition only) is given, the default for each field is its previous value.
A '+' can be specified instead of a number for size, which means as much as possible. This is useful with the -N option .
EXAMPLE（sfdisk 实例说明）
The commandsfdisk /dev/hdc << EOF
0,407 /*开始为0cylinders，大小为407cylinders*/
,407
;
;
EOF
will partition /dev/hdc just as indicated above.
The command
sfdisk /dev/hdb << EOF /* end of file (^D) 此指令没有声明单位，默认以cylinders单位分配大小 */
,3,L
,60,L
,19,S
,,E
,130,L
,130,L
,130,L
,,L
EOF
will partition /dev/hdb into two Linux partitions of 3 and 60 cylinders, a swap space of 19 cylinders, and an extended partition covering the rest. Inside the extended partition there are four Linux logical partitions, three of 130 cylinders and one covering the rest.
With the -x option, the number of input lines must be a multiple of 4: you have to list the two empty partitions that you never want using two blank lines. Without the -x option, you give one line for the partitions inside a extended partition, instead of four, and terminate with end-of-file (^D). (And sfdisk will assume that your input line represents the first of four, that the second one is extended, and the 3rd and 4th are empty.)
1、手头有个8G的U盘， U盘的设备号为/dev/sdb，想对其分区为: 第一分区200MB且作为启动盘， 第二分区5GB，剩余容量作为第三分区，可以这样输入：
wiwa@tech:~$ sudo sfdisk --in-order --Linux --unit M /dev/sdb << EOF
,200,L,*
,5120,L
,,L
EOF
wiwa@tech:~$ lsblk /dev/sdb
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb 8:16 1 7.4G 0 disk
├─sdb1 8:17 1 200M 0 part /media/wiwa/sdb1
├─sdb2 8:18 1 5G 0 part
└─sdb3 8:19 1 2.2G 0 part
wiwa@tech:~$ sudo fdisk -l /dev/sdb
Disk /dev/sdb: 7948 MB, 7948206080 bytes
245 heads, 62 sectors/track, 1021 cylinders, total 15523840 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 409599 204799+ 83 Linux
/dev/sdb2 409600 10895359 5242880 83 Linux
/dev/sdb3 10895360 15523839 2314240 83 Linux
wiwa@tech:~$ sudo sfdisk -l /dev/sdb
Disk /dev/sdb: 1021 cylinders, 245 heads, 62 sectors/track
Units = cylinders of 7777280 bytes, blocks of 1024 bytes, counting from 0
Device Boot Start End #cyls #blocks Id System
/dev/sdb1 * 0+ 26- 27- 204799+ 83 Linux
/dev/sdb2 26+ 717- 691- 5242880 83 Linux
/dev/sdb3 717+ 1021- 305- 2314240 83 Linux
/dev/sdb4 0 - 0 0 0 Empty
wiwa@tech:~$ sudo sfdisk -l -u S /dev/sdb
Disk /dev/sdb: 1021 cylinders, 245 heads, 62 sectors/track
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/sdb1 * 1 409599 409599 83 Linux
/dev/sdb2 409600 10895359 10485760 83 Linux
/dev/sdb3 10895360 15523839 4628480 83 Linux
/dev/sdb4 0 - 0 0 Empty
wiwa@tech:~$ sudo sfdisk -V /dev/sdb
Warning: partition 1 does not end at a cylinder boundary
Warning: partition 2 does not start at a cylinder boundary
Warning: partition 2 does not end at a cylinder boundary
Warning: partition 3 does not start at a cylinder boundary
Warning: partition 3 does not end at a cylinder boundary
end of partition 3 has impossible value for cylinders: 1021 (should be in 0-1020)
2、手头有个8G的U盘， 想对其分区为: 第一分区200MB且不作为启动盘， 第二分区5GB，剩余容量作为第三分区，可以这样输入：
wiwa@tech:~$ sudo sfdisk --in-order --Linux --unit M /dev/sdb << EOF
> ,200,L
> ,5120,L
> ,,L
> EOF
wiwa@tech:~$ sudo fdisk -l /dev/sdb
Disk /dev/sdb: 7948 MB, 7948206080 bytes
245 heads, 62 sectors/track, 1021 cylinders, total 15523840 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sdb1 1 409599 204799+ 83 Linux /*此处”*"号不见了*/
/dev/sdb2 409600 10895359 5242880 83 Linux
/dev/sdb3 10895360 15523839 2314240 83 Linux
wiwa@tech:~$ sudo sfdisk -V /dev/sdb
Warning: partition 1 does not end at a cylinder boundary
Warning: partition 2 does not start at a cylinder boundary
Warning: partition 2 does not end at a cylinder boundary
Warning: partition 3 does not start at a cylinder boundary
Warning: partition 3 does not end at a cylinder boundary
Warning: no primary partition is marked bootable (active)
This does not matter for LILO, but the DOS MBR will not boot this disk.
end of partition 3 has impossible value for cylinders: 1021 (should be in 0-1020)
3、手头有个8G的U盘， 想对其分区为: 第一分区200MB且作为启动盘（启动扇区从1MB处开始）， 第二分区5GB，剩余容量作为第三分区，可以这样输入：
wiwa@tech:~$ sudo sfdisk --in-order --Linux --unit M /dev/sdb << EOF
1,200,L,*
,5120,L
,,L
EOF
wiwa@tech:~$ sudo sfdisk -l -u S /dev/sdb
Disk /dev/sdb: 1021 cylinders, 245 heads, 62 sectors/track
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/sdb1 * 2048 411647 409600 83 Linux
/dev/sdb2 411648 10897407 10485760 83 Linux
/dev/sdb3 10897408 15523839 4626432 83 Linux
/dev/sdb4 0 - 0 0 Empty
wiwa@tech:~$ sudo sfdisk -l /dev/sdb
Disk /dev/sdb: 1021 cylinders, 245 heads, 62 sectors/track
Units = cylinders of 7777280 bytes, blocks of 1024 bytes, counting from 0
Device Boot Start End #cyls #blocks Id System
/dev/sdb1 * 0+ 27- 27- 204800 83 Linux
/dev/sdb2 27+ 717- 691- 5242880 83 Linux
/dev/sdb3 717+ 1021- 305- 2313216 83 Linux
/dev/sdb4 0 - 0 0 0 EmptyAVAILABILITY（可获取出处）
The sfdisk command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.*
备注：
本文的出处直接$ man sfdisk;
创建于20160203,wiwa