CentOS下如何完全干净卸载MySQL
CentOS下如何完全卸载MySQL？解决卸载不干净的问题
系统：CentOS 6.5，MySQL：MySql 5.6
虽然说这里的是使用rpm安装的卸载问题，我觉得使用yum方式安装的如果遇到相同的问题也一样适用。
查看已经安装的服务
rpm –qa|grep -i mysql
-i 作用是不区分大小写
yum remove mysql mysql-server mysql-libs compat-mysql51
rm -rf /var/lib/mysql
rm /etc/my.cnf
查看是否还有mysql软件：
rpm -qa|grep mysql
有的话继续删除
可以看到有两个安装包
MySQL-server-5.6.19-1.linux_glibc2.5.x86_64.rpm
MySQL-client-5.6.19-1.linux_glibc2.5.x86_64.rpm
删除这两个服务(去掉后缀)
rpm –e MySQL-client-5.6.19-1.linux_glibc2.5.x86_64
rpm -e MySQL-server-5.6.19-1.linux_glibc2.5.x86_64
查看残留的目录：
whereis mysql
然后删除mysql目录：
rm –rf /usr/lib64/mysql
删除相关文件：
rm –rf /usr/my.cnf
rm -rf /root/.mysql_sercret
最关键的：
rm -rf /var/lib/mysql
如果这个目录如果不删除，再重新安装之后，密码还是之前的密码，不会重新初始化！
网上查了很久都没有文章提到这个，最后还是自己摸索找出来的。
卸载完成！怎么确定是不是真的卸载干净了呢？
一是看安装输出：
如果没有卸载干净，安装server时输入只有两行：
[root @localhost opt]# rpm -ivh MySQL-server-5.6.19-1.linux_glibc2.5.x86_64.rpm
Preparing... ########################################### [100%]
1:MySQL-server ########################################### [100%]
卸载干净了安装输入如下：
[root @localhost opt]# rpm -ivh MySQL-server-5.6.19-1.linux_glibc2.5.x86_64.rpm
Preparing... ########################################### [100%]
1:MySQL-server ########################################### [100%]
2014-09-23 07:22:43 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2014-09-23 07:22:43 26041 [Note] InnoDB: Using atomics to ref count buffer pool pages
2014-09-23 07:22:43 26041 [Note] InnoDB: The InnoDB memory heap is disabled
2014-09-23 07:22:43 26041 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2014-09-23 07:22:43 26041 [Note] InnoDB: Compressed tables use zlib 1.2.3
2014-09-23 07:22:43 26041 [Note] InnoDB: Using Linux native AIO
2014-09-23 07:22:43 26041 [Note] InnoDB: Using CPU crc32 instructions
2014-09-23 07:22:43 26041 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2014-09-23 07:22:43 26041 [Note] InnoDB: Completed initialization of buffer pool
2014-09-23 07:22:43 26041 [Note] InnoDB: The first specified data file ./ibdata1 did not exist: a new database to be created!
2014-09-23 07:22:43 26041 [Note] InnoDB: Setting file ./ibdata1 size to 12 MB
2014-09-23 07:22:43 26041 [Note] InnoDB: Database physically writes the file full: wait...
2014-09-23 07:22:43 26041 [Note] InnoDB: Setting log file ./ib_logfile101 size to 48 MB
2014-09-23 07:22:43 26041 [Note] InnoDB: Setting log file ./ib_logfile1 size to 48 MB
2014-09-23 07:22:45 26041 [Note] InnoDB: Renaming log file ./ib_logfile101 to ./ib_logfile0
2014-09-23 07:22:45 26041 [Warning] InnoDB: New log files created, LSN=45781
2014-09-23 07:22:45 26041 [Note] InnoDB: Doublewrite buffer not found: creating new
2014-09-23 07:22:45 26041 [Note] InnoDB: Doublewrite buffer created
2014-09-23 07:22:45 26041 [Note] InnoDB: 128 rollback segment(s) are active.
2014-09-23 07:22:45 26041 [Warning] InnoDB: Creating foreign key constraint system tables.
2014-09-23 07:22:45 26041 [Note] InnoDB: Foreign key constraint system tables created
2014-09-23 07:22:45 26041 [Note] InnoDB: Creating tablespace and datafile system tables.
2014-09-23 07:22:45 26041 [Note] InnoDB: Tablespace and datafile system tables created.
2014-09-23 07:22:45 26041 [Note] InnoDB: Waiting for purge to start
2014-09-23 07:22:45 26041 [Note] InnoDB: 5.6.19 started; log sequence number 0
A random root password has been set. You will find it in '/root/.mysql_secret'.
2014-09-23 07:22:46 26041 [Note] Binlog end
2014-09-23 07:22:46 26041 [Note] InnoDB: FTS optimize thread exiting.
2014-09-23 07:22:46 26041 [Note] InnoDB: Starting shutdown...
2014-09-23 07:22:48 26041 [Note] InnoDB: Shutdown completed; log sequence number 1625977
2014-09-23 07:22:48 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2014-09-23 07:22:48 26065 [Note] InnoDB: Using atomics to ref count buffer pool pages
2014-09-23 07:22:48 26065 [Note] InnoDB: The InnoDB memory heap is disabled
2014-09-23 07:22:48 26065 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2014-09-23 07:22:48 26065 [Note] InnoDB: Compressed tables use zlib 1.2.3
2014-09-23 07:22:48 26065 [Note] InnoDB: Using Linux native AIO
2014-09-23 07:22:48 26065 [Note] InnoDB: Using CPU crc32 instructions
2014-09-23 07:22:48 26065 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2014-09-23 07:22:48 26065 [Note] InnoDB: Completed initialization of buffer pool
2014-09-23 07:22:48 26065 [Note] InnoDB: Highest supported file format is Barracuda.
2014-09-23 07:22:48 26065 [Note] InnoDB: 128 rollback segment(s) are active.
2014-09-23 07:22:48 26065 [Note] InnoDB: Waiting for purge to start
2014-09-23 07:22:48 26065 [Note] InnoDB: 5.6.19 started; log sequence number 1625977
2014-09-23 07:22:48 26065 [Note] Binlog end
2014-09-23 07:22:48 26065 [Note] InnoDB: FTS optimize thread exiting.
2014-09-23 07:22:48 26065 [Note] InnoDB: Starting shutdown...
2014-09-23 07:22:50 26065 [Note] InnoDB: Shutdown completed; log sequence number 1625987
A RANDOM PASSWORD HAS BEEN SET FOR THE MySQL root USER !
You will find that password in '/root/.mysql_secret'.
You must change that password on your first connect,
no other statement but 'SET PASSWORD' will be accepted.
See the manual for the semantics of the 'password expired' flag.
Also, the account for the anonymous user has been removed.
In addition, you can run:
/usr/bin/mysql_secure_installation
which will also give you the option of removing the test database.
This is strongly recommended for production servers.
See the manual for more instructions.
Please report any problems at http://bugs.mysql.com/
The latest information about MySQL is available on the web at
http://www.mysql.com
Support MySQL by buying support/licenses at http://shop.mysql.com
New default config file was created as /usr/my.cnf and
will be used by default by the server when you start it.
You may edit this file to change server settings
最后一段中提示了重要信息，很多人因为不喜欢读英文，导致接下来不知道怎么操作！
二就是安装完成，启动服务之后
使用命令：“mysql -uroot -p”输入你之前安装后设置的密码，看能不能登录，如果还可以登录，说明没有卸载干净！