fdisk /dev/sdb

Command (m for help): p

Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 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: 0x740e36e3
  Device Boot   Start     End   Blocks  Id System
/dev/sdb1       63   4194367   2097152+ 83 Linux
/dev/sdb2     4194368  16777215   6291424  5 Extended
/dev/sdb5     4194431   8388735   2097152+ 83 Linux
/dev/sdb6     8388799  16777215   4194208+ 83 Linux

//t命令：改写分区十六进制编码
Command (m for help): t 
Partition number (1-6): 6
//L命令可以查看不同分区的十六进制编码，交换分区为82
Hex code (type L to list codes): 82
Changed system type of partition 6 to 82 (Linux swap / Solaris)
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 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: 0x740e36e3
  Device Boot   Start     End   Blocks  Id System
/dev/sdb1       63   4194367   2097152+ 83 Linux
/dev/sdb2     4194368  16777215   6291424  5 Extended
/dev/sdb5     4194431   8388735   2097152+ 83 Linux
/dev/sdb6     8388799  16777215   4194208+ 82 Linux swap / Solaris
//分区表写入磁盘并退出
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.

mkswap /dev/sdb6
Setting up swapspace version 1, size = 4194204 KiB
no label, UUID=40eff2c0-3f6b-440e-bc2a-f71d3d5581a7

free
       total    used    free   shared  buffers   cached
Mem:    1030108   160768   869340    264   12040   56188
-/+ buffers/cache:   92540   937568
Swap:   6291352     0  6291352

/dev/sdb6        swap          swap  defaults    0 0
//查看交换分区
 swapon -s
Filename        Type    Size  Used  Priority
/dev/sda2                partition  2097148 0  -1
/dev/sdb6                partition  4194204 0  -2