CentOS 7 下MysqL 默认安装在/var/lib/MysqL目录下，但是随着存储数据的增多，所在的硬盘空间很快被占满，导致无法进行插入、建表等操作。
这时需要将MysqL数据存储文件夹移植到别的文件夹下，网上有很多教程，如http://www.cnblogs.com/5201351/p/4912614.html，是一篇很好的教程，但是在实际移植过程发现，只有MysqL的数据文件夹/var/lib/MysqL被改为其他目录，无论如何修改/etc/my.cnf配置中的datadir和socket参数，都无法移动MysqLd。
使用如下命令，启东MysqL
service MysqLd start
会出现如下错误：
Job for MysqLd.service Failed because the control process exited with error code. See "systemctl status MysqLd.service" and "journalctl -xe" for details.
如果使用如下命令查看
service MysqLd status
会得到如下错误信息
Redirecting to /bin/systemctl status MysqLd.service
● MysqLd.service - MysqL Server
Loaded: loaded (/usr/lib/systemd/system/MysqLd.service; enabled; vendor preset: disabled)
Active: Failed (Result: start-limit) since Fri 2017-10-20 09:03:33 CST; 1min 11s ago
Docs: man:MysqLd(8)
http://dev.MysqL.com/doc/refman/en/using-systemd.html
Process: 5130 ExecStart=/usr/sbin/MysqLd --daemonize --pid-file=/var/run/MysqLd/MysqLd.pid $MysqLD_OPTS (code=exited,status=1/FAILURE)
Process: 5108 ExecStartPre=/usr/bin/MysqLd_pre_systemd (code=exited,status=0/SUCCESS)
Main PID: 15110 (code=exited,status=0/SUCCESS)
Oct 20 09:03:33 bigdata-6 systemd[1]: Failed to start MysqL Server.
Oct 20 09:03:33 bigdata-6 systemd[1]: Unit MysqLd.service entered Failed state.
Oct 20 09:03:33 bigdata-6 systemd[1]: MysqLd.service Failed.
Oct 20 09:03:33 bigdata-6 systemd[1]: MysqLd.service holdoff time over,scheduling restart.
Oct 20 09:03:33 bigdata-6 systemd[1]: start request repeated too quickly for MysqLd.service
Oct 20 09:03:33 bigdata-6 systemd[1]: Failed to start MysqL Server.
Oct 20 09:03:33 bigdata-6 systemd[1]: Unit MysqLd.service entered Failed state.
Oct 20 09:03:33 bigdata-6 systemd[1]: MysqLd.service Failed.
一开始总以为是配置的问题，后来仔细查看一下msyql的日志文件： /var/log/MysqLd.log
出现了几个Warning，说文件无法创建
120609 11:31:31 MysqLd_safe MysqLd from pid file /var/run/MysqLd/MysqLd.pid ended
120609 11:35:12 MysqLd_safe Starting MysqLd daemon with databases from /mnt/hgfs/MysqL_data
120609 11:35:13 [Warning] Can't create test file /home/MysqL_data/data.lower-test
120609 11:35:13 [Warning] Can't create test file /home/MysqL_data/data.lower-test
/usr/libexec/MysqLd: Can't change dir to '/home/MysqL_data/' (Errcode: 13)
120609 11:35:13 [ERROR] Aborting
120609 11:35:13 [Note] /usr/libexec/MysqLd: Shutdown complete
120609 11:35:13 MysqLd_safe MysqLd from pid file /var/run/MysqLd/MysqLd.pid ended
解决方案：
关闭MysqL: service MysqLd stop
1、编辑/etc/selinux/config 文件，将其中的SELINUX禁用，SELINUX=disabled，重新启动系统。
2、移动/var/lib/MysqL到你需要的文件夹，mv /varlib/MysqL /home/MysqLdata
3、在/var/lib下创建一个链接ln -s /home/MysqLdata MysqL （这种方法可以不用修改my.cnf配置）
4、启动MysqL: service MysqLd start
记录一下，