日常运维--Linux添加swap分区方法

Linux添加swap分区方法（以整块盘或分区作为虚拟内存）

建立一个普通的Linux分区（主分区、逻辑分区均可）

[root@devops-fleming /]# fdisk -l

Disk /dev/vda: 44.0 GB, 44023414784 bytes, 85983232 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 label type: dos
Disk identifier: 0x000b1b45

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    85983198    42990575+  83  Linux

Disk /dev/vdb: 85.9 GB, 85899345920 bytes, 167772160 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 label type: dos
Disk identifier: 0x990f0d05

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048    83888127    41943040   83  Linux
/dev/vdb2        83888128   125831167    20971520   83  Linux
/dev/vdb3       125831168   167772159    20970496   83  Linux

以/dev/vdb3设为虚拟内存为例，可以看到分区的十六进制编码是83，即普通的Linux分区，而swap分区的编码是82。修改分区类型的十六进制编码，使用t命令改写分区十六进制编码

[root@devops-fleming /]# fdisk /dev/vdb
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): t
Partition number (1-3, default 3): 3
Hex code (type L to list all codes): 82
Changed type of partition 'Linux' to 'Linux swap / Solaris'

Command (m for help): p

Disk /dev/vdb: 85.9 GB, 85899345920 bytes, 167772160 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 label type: dos
Disk identifier: 0x990f0d05

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048    83888127    41943040   83  Linux
/dev/vdb2        83888128   125831167    20971520   83  Linux
/dev/vdb3       125831168   167772159    20970496   82  Linux swap / Solaris

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

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

可以看到/dev/vdb3的编码已经变成82 Linux swap / Solaris

格式化交换分区

[root@devops-fleming /]# mkswap /dev/vdb3
Setting up swapspace version 1, size = 20970492 KiB
no label, UUID=62976c8b-eeea-403c-914f-f6abfa735daf

启用交换分区

[root@devops-fleming /]# swapon /dev/vdb3

查看交换分区加载状态

[root@devops-fleming /]# free
              total        used        free      shared  buff/cache   available
Mem:        3880408      105288     2399132         500     1375988     3501300
Swap:      20970492           0    20970492

停用交换分区

[root@izj6c1me2wu2lepyg9fhg5z ~]# swapoff /dev/vdb3

不能直接使用mount命令挂载swap分区，因为swap分区是没有挂载点的。

系统启动时自动挂载，修改/etc/fstab配置文件

/dev/vdb3 swap swap defaults 0 0

查看交换分区

[root@devops-fleming /]# swapon -s
Filename				Type		Size	Used	Priority
/dev/vdb3                              	partition	20970492	0	-2