xtrabackup 详解（已纠正）

本文主要是介绍xtrabackup 详解（已纠正），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

xtrabackup是Percona公司CTO Vadim参与开发的一款基于InnoDB的在线热备工具，具有开源，免费，支持在线热备，备份恢复速度快，占用磁盘空间小等特点，并且支持不同情况下的多种备份形式。xtrabackup的官方下载地址为http://www.percona.com/software/percona-xtrabackup。

xtrabackup包含两个主要的工具，即xtrabackup和innobackupex，二者区别如下：

（1）xtrabackup只能备份innodb和xtradb两种引擎的表，而不能备份myisam引擎的表；

（2）innobackupex是一个封装了xtrabackup的Perl脚本，支持同时备份innodb和myisam，但在对myisam备份时需要加一个全局的读锁。还有就是myisam不支持增量备份。

1.备份过程

innobackupex备份过程如下图：

（图1 innobackupex备份过程,本文中所有图都是google所得）

在图1中，备份开始时首先会开启一个后台检测进程，实时检测mysql redo的变化，一旦发现redo中有新的日志写入，立刻将日志记入后台日志文件xtrabackup_log中。之后复制innodb的数据文件和系统表空间文件ibdata1，待复制结束后，执行flush tables with read lock操作，复制.frm，MYI，MYD，等文件（执行flush tableswith read lock的目的是为了防止数据表发生DDL操作，并且在这一时刻获得binlog的位置）最后会发出unlock tables，把表设置为可读可写状态，最终停止xtrabackup_log。

2.全备恢复

这一阶段会启动xtrabackup内嵌的innodb实例，回放xtrabackup日志xtrabackup_log，将提交的事务信息变更应用到innodb数据/表空间，同时回滚未提交的事务(这一过程类似innodb的实例恢复）。恢复过程如下图：

（图2 innobackupex 恢复过程）

3.增量备份

innobackupex增量备份过程中的"增量"处理，其实主要是相对innodb而言，对myisam和其他存储引擎而言，它仍然是全拷贝(全备份)

"增量"备份的过程主要是通过拷贝innodb中有变更的"页"（这些变更的数据页指的是"页"的LSN大于xtrabackup_checkpoints中给定的LSN）。增量备份是基于全备的，第一次增备的数据必须要基于上一次的全备，之后的每次增备都是基于上一次的增备，最终达到一致性的增备。增量备份的过程如下，和全备的过程很类似，区别仅在第2步。

（图 3 innobackupex增量备份过程）

4.增量备份恢复

和全备恢复类似，也需要两步，一是数据文件的恢复，如图4，这里的数据来源由3部分组成：全备份，增量备份和xtrabackup log。二是对未提交事务的回滚，如图5所示：

（图4 innobackupex 增量备份恢复过程1）

( 图5 innobackupex增量备份恢复过程2）

5.innobackupex使用示例

（1）安装使用xtrabackup，安装比较简单，我们使用二进制编译好的就行了，这种工具无需源码编译，因为没有什么功能需要俺们定制。

[root@MySQL-01 ~]# wget http://www.percona.com/redir/downloads/XtraBackup/LATEST/binary/Linux/x86_64/percona-xtrabackup-2.1.8-733-Linux-x86_64.tar.gz

[root@MySQL-01 ~]# tar xf percona-xtrabackup-2.1.8-733-Linux-x86_64.tar.gz -C /usr/local/
[root@MySQL-01 ~]# mv /usr/local/percona-xtrabackup-2.1.8-Linux-x86_64/ /usr/local/xtrabackup
[root@MySQL-01 ~]# echo "export PATH=\$PATH:/usr/local/xtrabackup/bin" >> /etc/profile
[root@MySQL-01 ~]# source /etc/profile
[root@MySQL-01 ~]#

（2）全量备份

创建备份用户：

mysql> create user 'backup'@'%' identified by 'yayun';
Query OK, 0 rows affected (0.01 sec)mysql> grant reload,lock tables,replication client,create tablespace,super on *.* to 'backup'@'%';
Query OK, 0 rows affected (0.00 sec)mysql>

进行全备份

备份数据存放在/data/backup/下面，innobackupex会自动创建一个文件夹，是当前系统的时间戳

mysql> select * from yayun.t1;
+------+-------+
| id   | name  |
+------+-------+
|    1 | yayun |
|    2 | atlas |
+------+-------+
2 rows in set (0.00 sec)mysql>

测试数据就是yayun库中的t1表（错误：--host=192.168.199.1

[root@MySQL-01 ~]# innobackupex --user=backup --password=yayun --socket=/tmp/mysqld.sock --defaults-file=/etc/my.cnf /data/backup/
xtrabackup: Creating suspend file '/data/backup/2014-04-07_23-05-04/xtrabackup_log_copied' with pid '57608'
xtrabackup: Transaction log of lsn (5324782783) to (5324782783) was copied.
140407 23:06:14  innobackupex: All tables unlocked
innobackupex: Backup created in directory '/data/backup/2014-04-07_23-05-04'
innobackupex: MySQL binlog position: filename 'mysql-bin.000014', position 2983
140407 23:06:14  innobackupex: Connection to database server closed
140407 23:06:14  innobackupex: completed OK!
[root@MySQL-01 ~]#

上面的过程中处理过，主要看最后是否提示innobackupex completed ok，可以看见备份成功。我们看看/data/backup目录下产生了什么

[root@MySQL-01 backup]# pwd
/data/backup
[root@MySQL-01 backup]# ll
total 4
drwxr-xr-x 12 root root 4096 Apr  7 23:06 2014-04-07_23-05-04
[root@MySQL-01 backup]# cd 2014-04-07_23-05-04/
[root@MySQL-01 2014-04-07_23-05-04]# ll
total 845888
-rw-r--r-- 1 root root       261 Apr  7 23:05 backup-my.cnf
drwx------ 2 root root      4096 Apr  7 23:06 employees
drwx------ 2 root root      4096 Apr  7 23:06 host
-rw-r----- 1 root root 866123776 Apr  7 23:05 ibdata1
drwx------ 2 root root      4096 Apr  7 23:06 menagerie
drwxr-xr-x 2 root root      4096 Apr  7 23:06 mysql
drwxr-xr-x 2 root root      4096 Apr  7 23:06 performance_schema
drwx------ 2 root root      4096 Apr  7 23:06 sakila
drwx------ 2 root root      4096 Apr  7 23:06 test
drwx------ 2 root root      4096 Apr  7 23:06 world_innodb
drwxr-xr-x 2 root root      4096 Apr  7 23:06 world_myisam
-rw-r--r-- 1 root root        13 Apr  7 23:06 xtrabackup_binary
-rw-r--r-- 1 root root        24 Apr  7 23:06 xtrabackup_binlog_info
-rw-r----- 1 root root        95 Apr  7 23:06 xtrabackup_checkpoints
-rw-r----- 1 root root      2560 Apr  7 23:06 xtrabackup_logfile
drwx------ 2 root root      4096 Apr  7 23:06 yayun
[root@MySQL-01 2014-04-07_23-05-04]#

可以看见有对应数据库的名字，比如yayun，还有一个以时间戳命名的目录。我们看看对应文件里面的内容，这几个比较重要

[root@MySQL-01 2014-04-07_23-05-04]# cat xtrabackup_checkpoints 
backup_type = full-backuped
from_lsn = 0
to_lsn = 5324782783
last_lsn = 5324782783
compact = 0
[root@MySQL-01 2014-04-07_23-05-04]# cat xtrabackup_binlog_info 
mysql-bin.000014        2983
[root@MySQL-01 2014-04-07_23-05-04]#

可以看见相关文件记录了LSN,日志偏移量，还可以看见这次是全备份，相信聪明的童鞋们一眼就看懂了。^_^

删除数据库，然后恢复全备（线上不要这样搞）

mysql> drop database yayun;
Query OK, 1 row affected (0.04 sec)mysql>

恢复全备

恢复备份到mysql的数据文件目录，这一过程要先关闭mysql数据库，重命名或者删除原数据文件目录都可以，再创建一个新的数据文件目录，将备份数据复制到新的数据文件目录下，赋权，修改权限，启动数据库

[root@MySQL-01 ~]# /etc/init.d/mysqld stop
Shutting down MySQL.....                                   [  OK  ]
[root@MySQL-01 ~]# mv /data/mysql /data/mysql_bak
[root@MySQL-01 ~]# mkdir /data/mysql
[root@MySQL-01 ~]#

[root@MySQL-01 ~]# innobackupex --apply-log /data/backup/2014-04-07_23-05-04/ 
xtrabackup: starting shutdown with innodb_fast_shutdown = 1
140407 23:22:36  InnoDB: Starting shutdown...
140407 23:22:40  InnoDB: Shutdown completed; log sequence number 5324784140
140407 23:22:40  innobackupex: completed OK!

以上对应的目录就是innobackupex全备份自己创建的目录。

[root@MySQL-01 ~]# innobackupex --defaults-file=/etc/my.cnf --copy-back --rsync /data/backup/2014-04-07_23-05-04/
innobackupex: Starting to copy InnoDB log files
innobackupex: in '/data/backup/2014-04-07_23-05-04'
innobackupex: back to original InnoDB log directory '/data/mysql'
innobackupex: Copying '/data/backup/2014-04-07_23-05-04/ib_logfile1' to '/data/mysql/ib_logfile1'
innobackupex: Copying '/data/backup/2014-04-07_23-05-04/ib_logfile0' to '/data/mysql/ib_logfile0'
innobackupex: Finished copying back files.
140407 23:27:38  innobackupex: completed OK!
[root@MySQL-01 ~]#

可以看见已经成功恢复，修改数据目录权限，启动mysql，效验数据是否正常，查看yayun库下面的t1表中的数据。

[root@MySQL-01 ~]# chown -R mysql.mysql /data/mysql
[root@MySQL-01 ~]# /etc/init.d/mysqld start
Starting MySQL.................                            [  OK  ]
[root@MySQL-01 ~]#

mysql> use yayun
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -ADatabase changed
mysql> select * from t1;
+------+-------+
| id   | name  |
+------+-------+
|    1 | yayun |
|    2 | atlas |
+------+-------+
2 rows in set (0.00 sec)mysql>

发现数据已经成功恢复。

（3）增量备份

在进行增量备份时，首先要进行一次全量备份，第一次增量备份是基于全备的，之后的增量备份是基于上一次的增量备份，以此类推。

全备份放在/data/backup/full,增量备份放在/data/backup/incremental

[root@MySQL-01 ~]# tree /data/backup/
/data/backup/
├── full
└── incremental2 directories, 0 files
[root@MySQL-01 ~]#

废话少说，咱们先来一次全备份

[root@MySQL-01 ~]# innobackupex --user=backup --password=yayun --socket=/tmp/mysqld.sock --defaults-file=/etc/my.cnf /data/backup/full/
innobackupex: Backup created in directory '/data/backup/full/2014-04-07_23-37-20'
innobackupex: MySQL binlog position: filename 'mysql-bin.000001', position 107
140407 23:38:29  innobackupex: Connection to database server closed
140407 23:38:29  innobackupex: completed OK!
[root@MySQL-01 ~]#

为了测试效果，我们在t1表中插入数据

mysql> select * from t1;
+------+-------+
| id   | name  |
+------+-------+
|    1 | yayun |
|    2 | atlas |
+------+-------+
2 rows in set (0.00 sec)mysql> insert into t1 select 1,'love sql';
Query OK, 1 row affected (0.01 sec)
Records: 1  Duplicates: 0  Warnings: 0mysql> select * from t1;                  
+------+----------+
| id   | name     |
+------+----------+
|    1 | yayun    |
|    2 | atlas    |
|    1 | love sql |
+------+----------+
3 rows in set (0.00 sec)mysql>

现在来一次增量备份1

[root@MySQL-01 ~]# innobackupex --user=backup --password=yayun --socket=/tmp/mysqld.sock --defaults-file=/etc/my.cnf --incremental /data/backup/incremental/ --incremental-basedir=/data/backup/full/2014-04-07_23-37-20/ --parallel=2
innobackupex: Backup created in directory '/data/backup/incremental/2014-04-07_23-42-46'
innobackupex: MySQL binlog position: filename 'mysql-bin.000001', position 301
140407 23:43:25  innobackupex: Connection to database server closed
140407 23:43:25  innobackupex: completed OK!
[root@MySQL-01 ~]#

我们看看增量备份的大小以及文件内容

[root@MySQL-01 ~]# du -sh /data/backup/full/2014-04-07_23-37-20/
1.2G    /data/backup/full/2014-04-07_23-37-20/
[root@MySQL-01 ~]# du -sh /data/backup/incremental/2014-04-07_23-42-46/
3.6M    /data/backup/incremental/2014-04-07_23-42-46/
[root@MySQL-01 ~]#

看见增量备份的数据很小吧，就是备份改变的数据而已。

[root@MySQL-01 2014-04-07_23-42-46]# pwd
/data/backup/incremental/2014-04-07_23-42-46
[root@MySQL-01 2014-04-07_23-42-46]# cat xtrabackup_checkpoints 
backup_type = incremental
from_lsn = 5324784718
to_lsn = 5324785066
last_lsn = 5324785066
compact = 0
[root@MySQL-01 2014-04-07_23-42-46]#

上面已经明显说明是增量备份了，该工具很人性化吧，呵呵

我们再次向t1表插入数据，然后创建增量备份2

mysql> select * from t1;
+------+----------+
| id   | name     |
+------+----------+
|    1 | yayun    |
|    2 | atlas    |
|    1 | love sql |
+------+----------+
3 rows in set (0.00 sec)mysql> insert into t1 select 1,'mysql dba';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0mysql> select * from t1;                   
+------+-----------+
| id   | name      |
+------+-----------+
|    1 | yayun     |
|    2 | atlas     |
|    1 | love sql  |
|    1 | mysql dba |
+------+-----------+
4 rows in set (0.00 sec)mysql>

创建增量备份2（这次是基于上次的增量备份哦）

[root@MySQL-01 ~]# innobackupex --user=backup --password=yayun --socket=/tmp/mysqld.sock --defaults-file=/etc/my.cnf --incremental /data/backup/incremental/ --incremental-basedir=/data/backup/incremental/2014-04-07_23-42-46/ --parallel=2
innobackupex: Backup created in directory '/data/backup/incremental/2014-04-07_23-51-15'
innobackupex: MySQL binlog position: filename 'mysql-bin.000001', position 496
140407 23:51:55  innobackupex: Connection to database server closed
140407 23:51:55  innobackupex: completed OK!
[root@MySQL-01 ~]#

[root@MySQL-01 ~]# ls -ltr /data/backup/full/
total 4
drwxr-xr-x 12 root root 4096 Apr  7 23:38 2014-04-07_23-37-20
[root@MySQL-01 ~]# ls -ltr /data/backup/incremental/
total 8
drwxr-xr-x 12 root root 4096 Apr  7 23:43 2014-04-07_23-42-46
drwxr-xr-x 12 root root 4096 Apr  7 23:51 2014-04-07_23-51-15
[root@MySQL-01 ~]#

（4）增量备份恢复

增量备份的恢复大体为3个步骤

*恢复完全备份

*恢复增量备份到完全备份（开始恢复的增量备份要添加--redo-only参数，到最后一次增量备份去掉--redo-only参数）

*对整体的完全备份进行恢复，回滚那些未提交的数据

恢复完全备份（注意这里一定要加--redo-only参数，该参数的意思是只应用xtrabackup日志中已提交的事务数据，不回滚还未提交的数据）

[root@MySQL-01 ~]# innobackupex --apply-log --redo-only /data/backup/full/2014-04-07_23-37-20/
xtrabackup: starting shutdown with innodb_fast_shutdown = 1
140407 23:59:43  InnoDB: Starting shutdown...
140407 23:59:43  InnoDB: Shutdown completed; log sequence number 5324784718
140407 23:59:43  innobackupex: completed OK!

将增量备份1应用到完全备份

[root@MySQL-01 ~]# innobackupex --apply-log --redo-only /data/backup/full/2014-04-07_23-37-20/ --incremental-dir=/data/backup/incremental/2014-04-07_23-42-46/
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-42-46/mysql/func.frm' to '/data/backup/full/2014-04-07_23-37-20/mysql/func.frm'
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-42-46/mysql/help_relation.frm' to '/data/backup/full/2014-04-07_23-37-20/mysql/help_relation.frm'
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-42-46/mysql/help_category.MYD' to '/data/backup/full/2014-04-07_23-37-20/mysql/help_category.MYD'
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-42-46/mysql/ndb_binlog_index.frm' to '/data/backup/full/2014-04-07_23-37-20/mysql/ndb_binlog_index.frm'
140408 00:02:07  innobackupex: completed OK!
[root@MySQL-01 ~]#

将增量备份2应用到完全备份（注意恢复最后一个增量备份时需要去掉--redo-only参数，回滚xtrabackup日志中那些还未提交的数据）

[root@MySQL-01 ~]# innobackupex --apply-log /data/backup/full/2014-04-07_23-37-20/ --incremental-dir=/data/backup/incremental/2014-04-07_23-51-15/
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-51-15/mysql/help_relation.frm' to '/data/backup/full/2014-04-07_23-37-20/mysql/help_relation.frm'
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-51-15/mysql/help_category.MYD' to '/data/backup/full/2014-04-07_23-37-20/mysql/help_category.MYD'
innobackupex: Copying '/data/backup/incremental/2014-04-07_23-51-15/mysql/ndb_binlog_index.frm' to '/data/backup/full/2014-04-07_23-37-20/mysql/ndb_binlog_index.frm'
140408 00:04:33  innobackupex: completed OK!
[root@MySQL-01 ~]#

把所有合在一起的完全备份整体进行一次apply操作，回滚未提交的数据：

[root@MySQL-01 ~]# innobackupex --apply-log /data/backup/full/2014-04-07_23-37-20/
xtrabackup: starting shutdown with innodb_fast_shutdown = 1
140408  0:06:32  InnoDB: Starting shutdown...
140408  0:06:36  InnoDB: Shutdown completed; log sequence number 5324785676
140408 00:06:36  innobackupex: completed OK!

把恢复完的备份复制到数据库目录文件中，赋权，然后启动mysql数据库，检测数据正确性

[root@MySQL-01 ~]# /etc/init.d/mysqld stop
Shutting down MySQL.                                       [  OK  ]
[root@MySQL-01 ~]# mv /data/mysql /data/mysql_bak
[root@MySQL-01 ~]# mkdir /data/mysql
[root@MySQL-01 ~]# innobackupex --defaults-file=/etc/my.cnf --copy-back --rsync /data/backup/full/2014-04-07_23-37-20/
innobackupex: Starting to copy InnoDB log files
innobackupex: in '/data/backup/full/2014-04-07_23-37-20'
innobackupex: back to original InnoDB log directory '/data/mysql'
innobackupex: Copying '/data/backup/full/2014-04-07_23-37-20/ib_logfile1' to '/data/mysql/ib_logfile1'
innobackupex: Copying '/data/backup/full/2014-04-07_23-37-20/ib_logfile0' to '/data/mysql/ib_logfile0'
innobackupex: Finished copying back files.
140408 00:12:42  innobackupex: completed OK!
[root@MySQL-01 ~]# chown -R mysql.mysql /data/mysql
[root@MySQL-01 ~]# /etc/init.d/mysqld start
Starting MySQL....                                         [  OK  ]
[root@MySQL-01 ~]#

查看数据是否正确

mysql> select * from t1;
+------+-----------+
| id   | name      |
+------+-----------+
|    1 | yayun     |
|    2 | atlas     |
|    1 | love sql  |
|    1 | mysql dba |
+------+-----------+
4 rows in set (0.00 sec)mysql>

（5）克隆slave

在日常工作中，我们有时候需要在线添加从库，比如线上有一主一从两个数据库，但是由于业务的需要，一台从库的读取无法满足现在的需求，这样就需要我们在线添加从库，由于出于安全考虑，我们通常需要在从库上进行在线克隆slave。

克隆slave时，常用参数--slave-info和--safe-slave-backup。

--slave-info会将master的binlog文件名和偏移量位置保存到xtrabackup_slave_info文件中

--safe-slave-backup会暂停slave的SQL线程直到没有打开的临时表的时候开始备份。备份结束后SQL线程会自动启动，这样操作的目的主要是确保一致性的复制状态。

下面的例子，将介绍一主一从情况下在线搭建新的从库，环境如下：

master 192.168.0.10 #主库

slave 192.168.0.20 #从库

newslave 192.168.0.100 # 新的从库

在上述示例中，newslave即为要新搭建的从库。在老的从库上面进行备份：

[root@MySQL-02 ~]# innobackupex --user=root --password=12345 --socket=/tmp/mysqld.sock --defaults-file=/etc/my.cnf --slave-info --safe-slave-backup --no-timestamp /data/cloneslave
innobackupex: Backup created in directory '/data/cloneslave'
innobackupex: MySQL binlog position: filename 'mysql-bin.000022', position 107
innobackupex: MySQL slave binlog position: master host '192.168.0.10', filename 'mysql-bin.000006', position 732
140413 23:25:13  innobackupex: completed OK!

这里的/data/cloneslave 目录要不存在，如果存在是会报错的。

查看目录下生成的文件：

[root@MySQL-02 ~]# ll /data/cloneslave/
total 26668
-rw-r--r-- 1 root root      261 Apr 13 23:24 backup-my.cnf
-rw-r--r-- 1 root root 27262976 Apr 13 23:24 ibdata1
drwxr-xr-x 2 root root     4096 Apr 13 23:25 mysql
drwxr-xr-x 2 root root     4096 Apr 13 23:25 performance_schema
drwxr-xr-x 2 root root     4096 Apr 13 23:25 sakila
drwxr-xr-x 2 root root     4096 Apr 13 23:25 world_innodb
-rw-r--r-- 1 root root       13 Apr 13 23:25 xtrabackup_binary
-rw-r--r-- 1 root root       23 Apr 13 23:25 xtrabackup_binlog_info
-rw-r--r-- 1 root root       79 Apr 13 23:25 xtrabackup_checkpoints
-rw-r--r-- 1 root root     2560 Apr 13 23:25 xtrabackup_logfile
-rw-r--r-- 1 root root       72 Apr 13 23:25 xtrabackup_slave_info
drwxr-xr-x 2 root root     4096 Apr 13 23:25 yayun
[root@MySQL-02 ~]#

查看xtrabackup_slave_info文件内容，这个内容就是为搭建从库时需要change master to的参数：

[root@MySQL-02 ~]# cat /data/cloneslave/xtrabackup_slave_info 
CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000006', MASTER_LOG_POS=732
[root@MySQL-02 ~]#

在老的slave服务器上进行还原，即192.168.0.20

[root@MySQL-02 ~]# innobackupex --apply-log --redo-only /data/cloneslave/
xtrabackup: starting shutdown with innodb_fast_shutdown = 1
140413 23:30:37  InnoDB: Starting shutdown...
140413 23:30:37  InnoDB: Shutdown completed; log sequence number 12981048
140413 23:30:37  innobackupex: completed OK!
[root@MySQL-02 ~]#

将还原的文件复制到新的从库newslave，即192.168.0.100

[root@MySQL-02 data]# rsync -avprP -e ssh /data/cloneslave/ 192.168.0.100:/data/mysql/

在主库master上添加对新从库newslave的授权：

mysql> grant replication slave on *.* to 'repl'@'192.168.0.100' identified by '123456';
Query OK, 0 rows affected (0.00 sec)mysql> flush privileges;
Query OK, 0 rows affected (0.02 sec)mysql>

拷贝老的从库的配置文件到新的从库newslave，并且修改server-id参数，修改完毕后，启动新的从库；

[root@MySQL-02 data]# scp /etc/my.cnf 192.168.0.100:/etc/root@192.168.0.100's password: my.cnf                                                                                                             100% 4881     4.8KB/s   00:00 
[root@MySQL-02 data]#

[root@newslave mysql]# egrep 'log-slave|^server-id|skip_slave' /etc/my.cnf 
server-id       = 3
skip_slave_start
log-slave-updates=1
[root@newslave mysql]#

[root@newslave mysql]# chown -R mysql.mysql .
[root@newslave mysql]# /etc/init.d/mysqld restart
Shutting down MySQL.                                       [  OK  ]
Starting MySQL..                                           [  OK  ]
[root@newslave mysql]#

查找老的从库备份后生成的xtrabackup_slave_info文件，提取其中的master_log_file和master_log_pos信息，然后在新的从库上进行change master to操作：

在新的从库上进行同步：

mysql> CHANGE MASTER TO MASTER_HOST='192.168.0.10',MASTER_USER='repl', MASTER_PASSWORD='123456',MASTER_LOG_FILE='mysql-bin.000006', MASTER_LOG_POS=732;
Query OK, 0 rows affected (0.09 sec)mysql>

启动io线程和sql线程，并观察复制是否正常：

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)mysql>

mysql> show slave  status\G
*************************** 1. row ***************************Slave_IO_State: Waiting for master to send eventMaster_Host: 192.168.0.10Master_User: replMaster_Port: 3306Connect_Retry: 2Master_Log_File: mysql-bin.000006Read_Master_Log_Pos: 1309Relay_Log_File: MySQL-02-relay-bin.000002Relay_Log_Pos: 830Relay_Master_Log_File: mysql-bin.000006Slave_IO_Running: YesSlave_SQL_Running: YesReplicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: yayun.%Replicate_Wild_Ignore_Table: Last_Errno: 0Last_Error: Skip_Counter: 0Exec_Master_Log_Pos: 1309Relay_Log_Space: 989Until_Condition: NoneUntil_Log_File: Until_Log_Pos: 0Master_SSL_Allowed: NoMaster_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: NoLast_IO_Errno: 0Last_IO_Error: Last_SQL_Errno: 0Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 1
1 row in set (0.00 sec)mysql>

查看主库，发现已经有两个线程(Binlog Dump)

mysql> show processlist\G
*************************** 1. row ***************************Id: 8User: slaveHost: 192.168.0.20:44251db: NULL
Command: Binlog DumpTime: 1088State: Master has sent all binlog to slave; waiting for binlog to be updatedInfo: NULL
*************************** 2. row ***************************Id: 9User: rootHost: localhostdb: yayun
Command: QueryTime: 0State: NULLInfo: show processlist
*************************** 3. row ***************************Id: 10User: replHost: 192.168.0.100:45844db: NULL
Command: Binlog DumpTime: 124State: Master has sent all binlog to slave; waiting for binlog to be updatedInfo: NULL
3 rows in set (0.00 sec)mysql>