free 命令用于显示当前系统中内存的使用量

1、查看当前内存

[root@happy ~]# free -m

             total       used       free     shared    buffers     cached

Mem:          1826       1706        120          8          0        531

-/+ buffers/cache:       1174        652

Swap:         2063          2       2061

2、创建用于交换分区的文件：增加2G大小的交换分区，count等于想要的块大小

[root@happy ~]# dd if=/dev/zero of=/home/swap bs=block_size count=number_of_block

dd: invalid number ‘block_size’

[root@happy ~]# dd if=/dev/zero of=/home/swap bs=1024 count=2048000

2048000+0 records in

2048000+0 records out

2097152000 bytes (2.1 GB) copied, 10.0768 s, 208 MB/s

3、设置交换分区文件

[root@happy ~]# mkswap /home/swap

Setting up swapspace version 1, size = 2047996 KiB

no label, UUID=2a8e8c81-fe4b-4111-ae60-715715cdb400

4、立即启用交换分区文件

[root@happy ~]# swapon /home/swap

swapon: /home/swap: insecure permissions 0644, 0600 suggested.

5、再次查看

[root@happy ~]# free -m

             total       used       free     shared    buffers     cached

Mem:          1826       1741         85          7          0        742

-/+ buffers/cache:        998        827

Swap:         4063         81       3982

6、如果想使得开机自启动，想要修改文件/etc/fastb 修改swap行

#

# /etc/fstab

# Created by anaconda on Mon May 14 16:09:52 2018

#

# Accessible filesystems, by reference, are maintained under '/dev/disk'

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

/dev/mapper/rhel-root   /                       xfs     defaults        1 1

UUID=6fef81a7-d81f-4a22-8795-f714054edb2e /boot                   xfs     defaults        1 2

/home/swap   swap                    swap    defaults        0 0

/mvp/RHEL-server-7.0-x86_64-LinuxProbe.Com.iso /mnt/cdrom iso9660 defaults,ro 0 0