Apache Replication 主从复制同步机制实践

1.两台server都安装Apache

apt-get install apache2

2.两台server都安装Rsync

apt-get install rsync

3.在ServerA使用cron做计划

crontab -e

进入编辑模式，然后输入下面内容，代表每5分钟会执行一次同步

5 * * * * rsync -avzhe ssh /var/www/

下面这个是配置的格式：

# ┌───────────── min (0 - 59)

# │ ┌────────────── hour (0 - 23)

# │ │ ┌─────────────── day of month (1 - 31)

# │ │ │ ┌──────────────── month (1 - 12)

# │ │ │ │ ┌───────────────── day of week (0 - 6) (0 to 6 are Sunday to Saturday, or use names; 7 is Sunday, the same as 0)

# │ │ │ │ │

# * * * * * command to execute

4.修改ServerB的/var/www/index.html的内容

5.检查ServerA的/var/www/index.html的内容被更新成ServerB一样的内容

（注意：为了让cron可以不输入密码直接执行rsync，需要设置下ssh-keygen如下：

# ssh-keygen

Generating public/private rsa key pair.

Enter file in which to save the key (/root/.ssh/id_rsa):

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /root/.ssh/id_rsa.

Your public key has been saved in /root/.ssh/id_rsa.pub.

The key fingerprint is:

a2:ff:3e:7b:2d:b4:98:27:0a:3d:1b:0b:98:51:98:3c

The key's randomart image is:

+--[ RSA 2048]----+

| |

| . o |

| E . |

| o |

| . . S |

| + o . . |

| o + + + o |

| + == = . |

| =++* . |

+-----------------+

/tmp

# ssh-copy-id -i /root/.ssh/id_rsa.pub machineBName

The authenticity of host 'machineBName (10.185.98.24)' can't be established.

RSA key fingerprint is cd:9d:d5:81:7b:38:3e:4c:41:0b:cb:72:de:51:03:da.

Are you sure you want to continue connecting (yes/no)? yes

/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed

/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys

password:

Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'machineBName"

and check to make sure that only the key(s) you wanted were added.

关于ssh-keygen可以参考：）