Linux中Swap（即：交换分区），类似于Windows的虚拟内存，就是当内存不足的时候，把一部分硬盘空间虚拟成内存使用,从而解决内存容量不足的情况。
交换分区的创建有两种方式：
1.使用实体分区创建swap
[[email protected] ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): n
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-20971519, default 2048): 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): 20971519
Partition 1 of type Linux and of size 10 GiB is set
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[[email protected] ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 120G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 119G 0 part
├─centos-root 253:0 0 50G 0 lvm /
├─centos-swap 253:1 0 3.8G 0 lvm [SWAP]
└─centos-home 253:2 0 65.2G 0 lvm /home
sdb 8:16 0 10G 0 disk
└─sdb1 8:17 0 10G 0 part
sr0 11:0 1 9.6G 0 rom
[[email protected] ~]# mkswap /dev/sdb1
Setting up swapspace version 1, size = 10484732 KiB
no label, UUID=9239bf77-27b3-44b1-9a52-7493f3403c2d
[[email protected] ~]# blkid /dev/sdb1
/dev/sdb1: UUID="9239bf77-27b3-44b1-9a52-7493f3403c2d" TYPE="swap"
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 188M 1.4G 9.5M 258M 1.5G
Swap: 3.7G 0B 3.7G
[[email protected] ~]# swapon /dev/sdb1
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 196M 1.4G 9.5M 258M 1.5G
Swap: 13G 0B 13G
[[email protected] ~]# swapon -s
Filename Type Size Used Priority
/dev/dm-1 partition 3932156 0 -2
/dev/sdb1 partition 10484732 0 -3
-------关闭swap分区操作------
[[email protected] ~]# swapoff /dev/sdb1
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 189M 1.4G 9.5M 258M 1.5G
Swap: 3.7G 0B 3.7G
[[email protected] ~]# swapon -s
Filename Type Size Used Priority
/dev/dm-1 partition 3932156 0 -22.使用文件创建swap
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 189M 1.4G 9.5M 258M 1.5G
Swap: 3.7G 0B 3.7G
[[email protected] ~]# dd if=/dev/zero of=/tmp/swap bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 5.90806 s, 182 MB/s
[[email protected] ~]# ll -h /tmp/swap
-rw-r--r--. 1 root root 1.0G Jul 8 14:33 /tmp/swap
[[email protected] ~]# swapon /tmp/swap
[[email protected] ~]# swapon -s
Filename Type Size Used Priority
/dev/dm-1 partition 3932156 0 -2
/tmp/swap file 1048572 0 -3
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 189M 341M 9.5M 1.3G 1.5G
Swap: 4.7G 0B 4.7G
-------关闭swap分区操作------
[[email protected] ~]# swapoff /tmp/swap
[[email protected] ~]# free -h
total used free shared buff/cache available
Mem: 1.8G 188M 342M 9.5M 1.3G 1.5G
Swap: 3.7G 0B 3.7GTIPS:最后记得设置开机自动挂载分区，关闭时也需注释掉新增配置（UUID执行blkid查找）
[[email protected] ~]# vim /etc/fstab
UUID="9239bf77-27b3-44b1-9a52-7493f3403c2d" swap swap defaults 0 0扩展：
swap分区使用优先级配置
1.查看当前swappiness值
swappiness=0的时候表示最大限度使用物理内存，然后才是 swap空间
swappiness＝100的时候表示积极的使用swap分区，并且把内存上的数据及时的搬运到swap空间里面
[[email protected] ~]# cat /proc/sys/vm/swappiness2.修改swappiness值为100（临时修改，重启后即还原为默认值）
[[email protected] ~]# sysctl vm.swappiness=100
3.永久修改swappiness默认值（重启生效）
[[email protected] ~]# vim /etc/sysctl.conf
vm.swappiness=100
Reference URL：《鸟哥的linux私房菜》