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fdisk 挺好学的，因为基本上按个m它就能告诉你该怎么做了。我这里有一个20g的虚拟磁盘。实际操作下。
开始对磁盘/dev/sdb分区
[root@rhel6 sjb]# fdisk /dev/sdb
WARNING: DOS-compatible mode is deprecated. It’s strongly recommended to
switch off the mode (command ‘c’) and change display units to
sectors (command ‘u’).
Command (m for help): m
Command action
a toggle a bootable flag 设置为启动分区
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition 删除分区
l list known partition types 显示已知的分区类型以及对应的id号
m print this menu 显示选项菜单
n add a new partition 新建分区
o create a new empty DOS partition table
p print the partition table 显示分区表
q quit without saving changes 不保存退出
s create a new empty Sun disklabel
t change a partition’s system id 改变分区id，即分区类型
u change display/entry units
v verify the partition table
w write table to disk and exit 写入分区表并退出
x extra functionality (experts only)
显示磁盘分区
Command (m for help): p
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xce4aaddb
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 131 1048576 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sdb2 131 784 5242880 83 Linux
Partition 2 does not end on cylinder boundary.
/dev/sdb3 784 1045 2097152 82 Linux swap / Solaris
Partition 3 does not end on cylinder boundary.
/dev/sdb4 1045 2611 12580864 f W95 Ext’d (LBA)
Partition 4 does not end on cylinder boundary.
/dev/sdb5 1045 2611 12579840 83 Linux
删除磁盘分区
Command (m for help): d
Partition number (1-5): 1
Command (m for help): d
Partition number (1-5): 2
Command (m for help): d
Partition number (1-5): 3
Command (m for help): d
Partition number (1-5): 4
Command (m for help): d
Partition number (1-5): 5
查看删除情况
Command (m for help): p
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xce4aaddb
Device Boot Start End Blocks Id System
新建主分区1，起始磁柱为1，分区大小我们用+100M来指定分区大小为100M.
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-2610, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-2610, default 2610): +100M
指定其为活动分区
Command (m for help): a
Partition number (1-6): 1
建立主分区2，大小为1G
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (15-2610, default 15):
Using default value 15
Last cylinder, +cylinders or +size{K,M,G} (15-2610, default 2610): +1G
查看支持的文件系统类型
Command (m for help): l
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx
5 Extended 42 SFS 86 NTFS volume set da Non-FS data
6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility
8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt
9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access
a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs
e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT
f W95 Ext’d (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 61 SpeedStor a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary
16 Hidden FAT16 64 Novell Netware af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 80 Old Minix be Solaris boot ff BBT
1e Hidden W95 FAT1
由上可以，swap代号id为83，将分区2变为swap分区
Command (m for help): t
Partition number (1-4): 2
Hex code (type L to list codes): 82
Changed system type of partition 2 to 82 (Linux swap / Solaris)
建立主分区3，大小为10G
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (147-2610, default 147):
Using default value 147
Last cylinder, +cylinders or +size{K,M,G} (147-2610, default 2610): +10G
建立扩展分区，将剩余空间全部划分给它
Command (m for help): n
Command action
e extended
p primary partition (1-4)
e
Selected partition 4
First cylinder (1453-2610, default 1453):
Using default value 1453
Last cylinder, +cylinders or +size{K,M,G} (1453-2610, default 2610):
Using default value 2610
在扩展分区下建立两个逻辑分区，一个大小5g,一个使用剩余全部扩展分区空间。注意，在这里我们新建的时候，已经没有提示我们要建立主分区还是扩展分区了，因为系统中除了扩展分区外没有其它额外空间了，所以直接进入就扩展分区了。另外，在扩展分区下建立逻辑分区是不用指定分区号的，系统会自动从5开始向后编号，如我们现在的建立的分区就是/dev/sdb5。
Command (m for help): n
First cylinder (1453-2610, default 1453):
Using default value 1453
Last cylinder, +cylinders or +size{K,M,G} (1453-2610, default 2610): +5G
Command (m for help): n
First cylinder (2107-2610, default 2107):
Using default value 2107
Last cylinder, +cylinders or +size{K,M,G} (2107-2610, default 2610):
Using default value 2610
查看磁盘分区情况，可以看到，我们建立的几个分区都建立好了。并且sdb1是活动的。
Command (m for help): p
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xce4aaddb
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 14 112423+ 83 Linux
/dev/sdb2 15 146 1060290 82 Linux swap / Solaris
/dev/sdb3 147 1452 10490445 83 Linux
/dev/sdb4 1453 2610 9301635 5 Extended
/dev/sdb5 1453 2106 5253223+ 83 Linux
/dev/sdb6 2107 2610 4048348+ 83 Linux
将修改写入磁盘
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
查看新磁盘的分区情况
[root@rhel6 sjb]# fdisk -l /dev/sdb
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xce4aaddb
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 14 112423+ 83 Linux
/dev/sdb2 15 146 1060290 82 Linux swap / Solaris
/dev/sdb3 147 1452 10490445 83 Linux
/dev/sdb4 1453 2610 9301635 5 Extended
/dev/sdb5 1453 2106 5253223+ 83 Linux
/dev/sdb6 2107 2610 4048348+ 83 Linux
可以看到，分区成功了！当然，这时还不能用啊，因为还没格式化呢！
