双向同步镜像软件Unison！！！

项目背景：

公司有两台服务器，A和B，需要保持A和B的数据完全一致，任何一台服务器数据改变，都会更新到另一台！

实验环境：

vmware workstation 11

服务器A：ip：192.168.0.19  iptables关闭  setenforce 0

服务器B：ip：192.168.0.12  iptables关闭  setenforce 0

SecureCRT （ssh远程连接软件）

实验流程：

一、配置双机ssh信任

下面这个连接是我写的如何配置双机ssh信任的教程

http://9399369.blog.51cto.com/9389369/1750915

二、unison软件安装

直接用yum安装

[root@baculaServer  ~]# yum install -y unison   #主机A上

[root@Slave-drbd ~]# yum install -y unison #主机B上

安装完以后就直接可以用了。

三、本地使用unison

1：创建测试目录test1 test2

[root@baculaServer  ~]# mkdir test1 test2

2:在test1里面创建两个测试文件，test2不做修改

[root@baculaServer  ~]# cd test1/

[root@baculaServer  test1]# ifconfig >testfile1.txt

[root@baculaServer  test1]# ping -c 3 www.baidu.com >testfile2.txt

3：数据同步

[root@baculaServer  ~]# unison test1 test2 -batch           # -batch             batch mode: ask no questions at all

Contacting server...

Connected [//baculaServer //root/test1 -> //baculaServer //root/test2]

Looking for changes

Reconciling changes

deleted  ---->            hgfs  

test1        : deleted

test2        : unchanged dir      modified on 2016-03-14 at  0:54:37  size 0         rwxr-xr-x

new file ---->            test1.txt  

test1        : new file           modified on 2016-03-14 at  1:15:57  size 889       rw-r--r--

test2        : absent

new file ---->            test2  

test1        : new file           modified on 2016-03-14 at  1:16:19  size 548       rw-r--r--

test2        : absent

Propagating updates

UNISON 2.27.57 started propagating changes at 01:17:41 on 14 Mar 2016

[BGN] Copying test1.txt from /root/test1 to /root/test2

[END] Copying test1.txt

[BGN] Copying test2 from /root/test1 to /root/test2

[END] Copying test2

[BGN] Deleting hgfs from /root/test2

[END] Deleting hgfs

UNISON 2.27.57 finished propagating changes at 01:17:41 on 14 Mar 2016

Saving synchronizer state

Synchronization complete  (3 items transferred, 0 skipped, 0 failures)

4：测试

[root@baculaServer  ~]# cd test2

[root@baculaServer  test2]# ls

test1.txt  test2

可以看到我们没有创建这俩文件在test2目录，但是现在出现了！！！yes

四、远程使用unison

[root@baculaServer  ~]# unison /test1 ssh://root@192.168.0.12//mnt -batch

Contacting server...

Connected [//Slave-drbd//mnt -> //baculaServer //test1]

Looking for changes

Warning: No archive files were found for these roots, whose canonical names are:

        /test1

        //Slave-drbd//mnt

This can happen either

because this is the first time you have synchronized these roots, 

or because you have upgraded Unison to a new version with a different

archive format.  

Update detection may take a while on this run if the replicas are 

large.

Unison will assume that the 'last synchronized state' of both replicas

was completely empty.  This means that any files that are different

will be reported as conflicts, and any files that exist only on one

replica will be judged as new and propagated to the other replica.

If the two replicas are identical, then no changes will be reported.

If you see this message repeatedly, it may be because one of your machines

is getting its address from DHCP, which is causing its host name to change

between synchronizations.  See the documentation for the UNISONLOCALHOSTNAME

environment variable for advice on how to correct this.

Donations to the Unison project are gratefully accepted: 

http://www.cis.upenn.edu/~bcpierce/unison

  Waiting for changes from server

Reconciling changes

         <---- dir        /  

local        : absent

Slave-drbd   : dir                modified on 2016-03-14 at  1:22:20  size 0         rwxr-xr-x

Propagating updates

UNISON 2.27.57 started propagating changes at 01:23:58 on 14 Mar 2016

[BGN] Copying  from //Slave-drbd//mnt to /test1

[END] Copying 

UNISON 2.27.57 finished propagating changes at 01:23:58 on 14 Mar 2016

Saving synchronizer state

Synchronization complete  (1 item transferred, 0 skipped, 0 failures)

查看服务器B

[root@Slave-drbd ~]# cd /mnt/

[root@Slave-drbd mnt]# ls

hgfs  testfile1.txt  testfile2.txt 

可以看到我们多增的这两个文件。

五、删除B服务器的ifconfig.txt，看一下能不能同步成功

这是在服务器B上执行的：

[root@Web1 tmp]# \rm ifconfig.txt 

[root@Web1 tmp]# cat ifconfig.txt 

cat: ifconfig.txt: No such file or directory

在服务器A上执行同步命令

[root@Server  fuchao1]# unison /fuchao1/ ssh://root@192.168.0.12//tmp -batch

查看/fuchao1目录

[root@Server  fuchao1]# ls

ks-script-HprTeo      virtual-02.bd0Nzs  VMwareDnD

ks-script-HprTeo.log  virtual-02.Nvhjul  vmware-root

ping.txt              vmware-02          yum.log

pulse-eft3MC9bdiQw    vmware-config0     yum_save_tx-2016-03-14-00-51vq7ClS.yumtx

可以看到我们现在/fuchao1目录和服务器B/tmp目录的一模一样！！！！

总结：双向同步更新，有时候特别有用！希望大家能在实际的生产中懂得它的妙用！谢谢大家！！