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
这里主要解决使用rpm安装的卸载问题，安装方法见：CentOS安装MySQL*.rpm提示conflicts with file from package的解决办法 见
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