swap交换文件和分区

作者/来源：yixinu.com

栏目：运维/编程

日期：2012-04-11 11:42:44

1、增加swap交换分区

将分区修改为SWAP分区格式 
[root@bogon mydata]# fdisk /dev/sdb
……

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    20971519    10484736    5  Extended
/dev/sdb5            4096     2101247     1048576   83  Linux
/dev/sdb6         2103296     4200447     1048576   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)
……

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    20971519    10484736    5  Extended
/dev/sdb5            4096     2101247     1048576   83  Linux
/dev/sdb6         2103296     4200447     1048576   82  Linux swap / Solaris
……
[root@bogon mydata]# mkswap /dev/sdb6
/dev/sdb6: No such file or directory
……
[root@bogon mydata]# partx -a /dev/sdb

mkswap写入SWAP 标签 
[root@bogon mydata]# mkswap /dev/sdb6
Setting up swapspace version 1, size = 1048572 KiB
no label, UUID=dad4ca71-33c1-4d97-937e-b87a0263ff8a
……

激活SWAP文件系统
[root@bogon mydata]# swapon /dev/sdb6

查看内存
[root@bogon mydata]# top
……
Swap:  2096120k total,        0k used,  2096120k free,   112824k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
……

[root@bogon mydata]# swapoff /dev/sdb6
……
Swap:  1047548k total,        0k used,  1047548k free,   131788k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND

swap -s 显示正在使用的SWAP信息

[root@bogon mydata]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1047548 0       -1
/dev/sdb6                               partition       1048572 0       -2

优先级的问题：

数值越大，优先级越高

调整SWAP优先级：

[root@bogon mydata]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1047548 0       -1
/dev/sdb6                               partition       1048572 0       -2
[root@bogon mydata]# swapoff /dev/sdb6
[root@bogon mydata]# swapon -p 10 /dev/sdb6
[root@bogon mydata]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1047548 0       -1
/dev/sdb6                               partition       1048572 0       10
[root@bogon mydata]#

2、使用文件作为 swap

步骤：

1、创建一个空文件

[root@bogon mydata]# dd if=/dev/zero of=/1000M.swap bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 157.195 s, 6.8 MB/s

2、写入数字签名

[root@bogon mydata]# mkswap /1000M.swap 
Setting up swapspace version 1, size = 1048572 KiB
no label, UUID=c62925e2-55e3-42fa-a58f-c20fba92137c

3、激活

[root@bogon mydata]# swapon -p 9 /1000M.swap

[root@bogon mydata]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1047548 0       -1
/dev/sdb6                               partition       1048572 0       10
/1000M.swap                             file            1048572 0       9

3、写入/etc/fstab

/1000M.swap     swap    swap    defaults        0 0