现象：把/var/lib/mysql下的数据文件移动到其他目录下，之后发现启动mysql报错，并且mysql无法运行。具体的操作如下：
# service mysql stop # mv /var/lib/mysql /data # serivce mysql start
报出的错误信息为：
170425 9:55:36 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead. 170425 9:55:36 [Note] Plugin 'FEDERATED' is disabled. /usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13) 170425 9:55:36 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. 170425 9:55:36 InnoDB: The InnoDB memory heap is disabled 170425 9:55:36 InnoDB: Mutexes and rw_locks use GCC atomic builtins 170425 9:55:36 InnoDB: Compressed tables use zlib 1.2.8 170425 9:55:36 InnoDB: Using Linux native AIO 170425 9:55:36 InnoDB: Initializing buffer pool, size = 128.0M 170425 9:55:36 InnoDB: Completed initialization of buffer pool 170425 9:55:36 InnoDB: Operating system error number 13 in a file operation. InnoDB: The error means mysqld does not have the access rights to InnoDB: the directory. InnoDB: File name ./ibdata1 InnoDB: File operation call: 'open'. InnoDB: Cannot continue operation.
原因
最初以为是简单的权限问题，就把/data/mysql目录赋权给mysql用户
# chown -R mysql:mysql /data/mysql
但是再次启动mysql后，还是遇到同样的错误。上网查了一下，原因是由于现今的Linux系统都采用AppArmor来限制文件和目录的执行权限。
解决办法
所以需要配置AppArmor让mysqld可以访问/data/mysql目录。具体操作如下：
# vi /etc/apparmor.d/usr.sbin.mysqld
在此文件末尾增加你的目录（可以按照/var/lib/mysql的目录改）
/usr/sbin/mysqld {
#include <abstractions/base>
#include <abstractions/nameservice>
#include <abstractions/user-tmp>
#include <abstractions/mysql>
#include <abstractions/winbind>
capability dac_override,
capability sys_resource,
capability setgid,
capability setuid,
network tcp,
/etc/hosts.allow r,
/etc/hosts.deny r,
/etc/mysql/*.pem r,
/etc/mysql/conf.d/ r,
/etc/mysql/conf.d/* r,
/etc/mysql/*.cnf r,
/usr/lib/mysql/plugin/ r,
/usr/lib/mysql/plugin/*.so* mr,
/usr/sbin/mysqld mr,
/usr/share/mysql/** r,
/var/log/mysql.log rw,
/var/log/mysql.err rw,
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,
/var/lib/mysql-files/ r,
/var/lib/mysql-files/** rwk,
/var/log/mysql/ r,
/var/log/mysql/* rw,
/var/run/mysqld/mysqld.pid rw,
/var/run/mysqld/mysqld.sock w,
/run/mysqld/mysqld.pid rw,
/run/mysqld/mysqld.sock w,
/sys/devices/system/cpu/ r,
# Site-specific additions and overrides. See local/README for details.
#include <local/usr.sbin.mysqld>
/data/mysql/ r,
/data/mysql/** rwk,
}
如果不写第一句的/data/mysql/ r，则mysql能启动，但是进入mysql后输入命令会提示下面错误：
ERROR 1018 (HY000): Can't read dir of '.' (errno: 13
