最多只能分四个主分区，如果要建多于四个的分区，就要拿出一个主分区做为扩展分区

使用fdisk进行分区

[root@localhost ~]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

The number of cylinders for this disk is set to 1305.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): p    //使用p列出设备现有的分区

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): n    //使用n新增一个分区

Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1305, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-1305, default 1305): +300m

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (38-1305, default 38):
Using default value 38
Last cylinder or +size or +sizeM or +sizeK (38-1305, default 1305): +300m

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux
/dev/sdb2              38          74      297202+  83  Linux

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (75-1305, default 75):
Using default value 75
Last cylinder or +size or +sizeM or +sizeK (75-1305, default 1305): +600m

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux
/dev/sdb2              38          74      297202+  83  Linux
/dev/sdb3              75         148      594405   83  Linux

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
e
Selected partition 4
First cylinder (149-1305, default 149):
Using default value 149
Last cylinder or +size or +sizeM or +sizeK (149-1305, default 1305):
Using default value 1305

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux
/dev/sdb2              38          74      297202+  83  Linux
/dev/sdb3              75         148      594405   83  Linux
/dev/sdb4             149        1305     9293602+   5  Extended

Command (m for help): n
First cylinder (149-1305, default 149):
Using default value 149
Last cylinder or +size or +sizeM or +sizeK (149-1305, default 1305): +2000m

Command (m for help): n
First cylinder (393-1305, default 393):
Using default value 393
Last cylinder or +size or +sizeM or +sizeK (393-1305, default 1305): +200m

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux
/dev/sdb2              38          74      297202+  83  Linux
/dev/sdb3              75         148      594405   83  Linux
/dev/sdb4             149        1305     9293602+   5  Extended
/dev/sdb5             149         392     1959898+  83  Linux
/dev/sdb6             393         417      200781   83  Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

建好分区后，还可以更改相关分区的文件系统类型

如，我们把第二个主分区改成linux下的交换分区

[root@localhost ~]# fdisk /dev/sdb

The number of cylinders for this disk is set to 1305.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): t    //更改文件系统类型
Partition number (1-6): 2 
Hex code (type L to list codes): L    //要更改文件系统编码

 0  Empty           1e  Hidden W95 FAT1 80  Old Minix       bf  Solaris       
 1  FAT12           24  NEC DOS         81  Minix / old Lin c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          82  Linux swap / So c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  83  Linux           c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     84  OS/2 hidden C:  c7  Syrinx         
 5  Extended        41  PPC PReP Boot   85  Linux extended  da  Non-FS data   
 6  FAT16           42  SFS             86  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS       4d  QNX4.x          87  NTFS volume set de  Dell Utility  
 8  AIX             4e  QNX4.x 2nd part 88  Linux plaintext df  BootIt        
 9  AIX bootable    4f  QNX4.x 3rd part 8e  Linux LVM       e1  DOS access    
 a  OS/2 Boot Manag 50  OnTrack DM      93  Amoeba          e3  DOS R/O       
 b  W95 FAT32       51  OnTrack DM6 Aux 94  Amoeba BBT      e4  SpeedStor     
 c  W95 FAT32 (LBA) 52  CP/M            9f  BSD/OS          eb  BeOS fs       
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi ee  EFI GPT       
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a5  FreeBSD         ef  EFI (FAT-12/16/
10  OPUS            55  EZ-Drive        a6  OpenBSD         f0  Linux/PA-RISC b
11  Hidden FAT12    56  Golden Bow      a7  NeXTSTEP        f1  SpeedStor     
12  Compaq diagnost 5c  Priam Edisk     a8  Darwin UFS      f4  SpeedStor     
14  Hidden FAT16 <3 61  SpeedStor       a9  NetBSD          f2  DOS secondary 
16  Hidden FAT16    63  GNU HURD or Sys ab  Darwin boot     fb  VMware VMFS   
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fe  LANstep       
1c  Hidden W95 FAT3 75  PC/IX           be  Solaris boot    ff  BBT           
Hex code (type L to list codes): 82
Changed system type of partition 2 to 82 (Linux swap / Solaris)

Command (m for help): P

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          37      297171   83  Linux
/dev/sdb2              38          74      297202+  82  Linux swap / Solaris
/dev/sdb3              75         148      594405   83  Linux
/dev/sdb4             149        1305     9293602+   5  Extended
/dev/sdb5             149         392     1959898+  83  Linux
/dev/sdb6             393         417      200781   83  Linux

Command (m for help): w   //保存
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.