我们知道 CPU 计算与数据的存储都会使用到内存，使用内存可以大大减少从磁盘读取的时间，但是当物理内存不足时，就需要暂时将用不到的程序和数据挪到内存交换空间(swap)
作法：
1.创建分区（fdisk ,文件）
2.格式化为 swap
3.启动
4.查看
创建分区
举例
[root@bogon ~]# fdisk /dev/sda
The number of cylinders for this disk is set to 2610.
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): p
Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1288 10241437+ 83 Linux
/dev/sda3 1289 1925 5116702+ 83 Linux
/dev/sda4 1926 2610 5502262+ 5 Extended
/dev/sda5 1926 2052 1020096 82 Linux swap / Solaris
/dev/sda6 2053 2115 506016 83 Linux
Command (m for help): t
Partition number (1-6): 6
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/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1288 10241437+ 83 Linux
/dev/sda3 1289 1925 5116702+ 83 Linux
/dev/sda4 1926 2610 5502262+ 5 Extended
/dev/sda5 1926 2052 1020096 82 Linux swap / Solaris
/dev/sda6 2053 2115 506016 82 Linux swap / Solaris
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: 设备或资源忙.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
part[root@bogon ~]# partprobe
这里需要在进行设置下 system ID格式化
语法：mkswap 设备名称
举例
[root@bogon ~]# mkswap /dev/sda6
Setting up swapspace version 1, size = 518156 kB启动|关闭
语法：swapon [-s]设备名称
swapoff 设备名称
选项与参数：
-s:查看所有 swap 文件系统
举例1：启动 swap
[root@bogon ~]# swapon /dev/sda6举例2：查看所有 swap