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content/小白手册/服务器日常/ecs添加swap.md

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+查看当前是没有swap的
+
+ 
+
+```bash
+$ free -m
+
+​       total    used    free   shared  buffers   cached
+
+Mem:      498    310    187     0     17    170
+
+-/+ buffers/cache:    122    375
+
+Swap:      0     0     0
+
+
+
+
+$ sudo df -hT
+
+Filesystem   Type  Size Used Avail Use% Mounted on
+
+/dev/xvda1   ext4  20G 3.7G  16G 20% /
+
+tmpfs     tmpfs 250M   0 250M  0% /dev/shm
+```
+
+
+
+ 
+
+
+
+ 
+
+我们将swap挂载到/var下
+
+ 
+
+$ sudo dd if=/dev/zero of=/var/swap bs=1M count=2048
+
+2048+0 records in
+
+2048+0 records out
+
+2147483648 bytes (2.1 GB) copied, 47.8375 s, 44.9 MB/s
+
+ 
+
+ 
+
+$ sudo mkswap /var/swap
+
+ 
+
+$ sudo chmod 0600 /var/swap
+
+ 
+
+$ sudo swapon /var/swap
+
+ 
+
+挂载完毕后，查看内存使用情况。发现swap出现了。
+
+ 
+
+[root@iZ23zvh0w6mZ lnmp1.1-full]# free -m
+
+​       total    used    free   shared  buffers   cached
+
+Mem:      498    456     41     0     10    100
+
+-/+ buffers/cache:    346    152
+
+Swap:     2047     0    2047
+
+ 
+
+ 
+
+ok，swap已经可以使用了，接下来我们要将swap开机自动挂载。
+
+编辑/etc/fstab文件
+
+ 
+
+$ sudo vi /etc/fstab
+
+\#
+
+\# /etc/fstab
+
+\# Created by anaconda on Mon Aug 11 16:27:41 2014
+
+\#
+
+\# 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
+
+\#
+
+UUID=e76a7b8d-20c2-4f94-bdd1-f4054a34c206 / ext4 defaults,barrier=0 1 1
+
+tmpfs          /dev/shm        tmpfs  defaults    0 0
+
+devpts         /dev/pts        devpts gid=5,mode=620 0 0
+
+sysfs          /sys          sysfs  defaults    0 0
+
+proc          /proc          proc  defaults    0 0
+
+none         /proc/xen        xenfs  defaults    0 0
+
+/var/swap        swap          swap  defaults    0 0
+
+因为阿里云默认是不让用户使用swap的（貌似现在的系统模版更新了，这一行新装系统都没有了，如果没有请忽略此步。）。
+
+编辑/etc/rc.d/rc.local文件，将文件中的swapoff行注释或删掉。
+
+ 
+
+$ sudo vi /etc/rc.d/rc.local 
+
+\#!/bin/sh
+
+\#
+
+\# This script will be executed *after* all the other init scripts.
+
+\# You can put your own initialization stuff in here if you don't
+
+\# want to do the full Sys V style init stuff.
+
+ 
+
+touch /var/lock/subsys/local
+
+ulimit -SHn 65535
+
+\#swapoff -a //加上"#"号注释掉或者直接删除