MySQL的坑 Can't find file: './mysql/plugin.frm' 问题

MySQL的磁盘满了，将数据库目录data移动到/data3目录，/etc/my.cnf里面也修改了相应的datadir目录，权限也赋予了，但是service mysql start;的时候报错，error log显示如下：

2017-09-15 16:01:01 2420 [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.2017-09-15 16:01:01 2420 [Note] Plugin 'FEDERATED' is disabled.^G/usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13 - Permission denied)2017-09-15 16:01:01 2420 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.2017-09-15 16:01:01 2420 [Note] InnoDB: Using atomics to ref count buffer pool pages2017-09-15 16:01:01 2420 [Note] InnoDB: The InnoDB memory heap is disabled2017-09-15 16:01:01 2420 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins2017-09-15 16:01:01 2420 [Note] InnoDB: Memory barrier is not used2017-09-15 16:01:01 2420 [Note] InnoDB: Compressed tables use zlib 1.2.82017-09-15 16:01:01 2420 [Note] InnoDB: Using Linux native AIO2017-09-15 16:01:01 2420 [Note] InnoDB: Using CPU crc32 instructions2017-09-15 16:01:01 2420 [Note] InnoDB: Initializing buffer pool, size = 128.0M2017-09-15 16:01:02 2420 [Note] InnoDB: Completed initialization of buffer pool2017-09-15 16:01:02 2420 [ERROR] InnoDB: ./ibdata1 can't be opened in read-write mode2017-09-15 16:01:02 2420 [ERROR] InnoDB: The system tablespace must be writable!2017-09-15 16:01:02 2420 [ERROR] Plugin 'InnoDB' init function returned error.2017-09-15 16:01:02 2420 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.2017-09-15 16:01:02 2420 [ERROR] Unknown/unsupported storage engine: InnoDB2017-09-15 16:01:02 2420 [ERROR] Aborting

去先检查plugin.frm权限，发现有权限，也是mysql属主：

root@hutaojie-1-pdd-sh:/data1/mysql/mysql# ll plugin.*-rwxrwxrwx 1 mysql mysql 8586 Mar  6  2016 plugin.frm*-rwxrwx--x 1 mysql mysql  116 Mar  6  2016 plugin.MYD*-rwxrwx--x 1 mysql mysql 2048 Mar  6  2016 plugin.MYI*root@hutaojie-1-pdd-sh:/data1/mysql/mysql#

google之后发现，原来问题在os这里，ubatu的mysql通过yum安装或者rpm安装的时候，会建一个/etc/apparmor.d/usr.sbin.mysqld 文件，如果数据目录不在这里面，则会报错，

/usr/sbin/mysqld: Can’t find file: ‘./mysql/plugin.frm’ (errno: 13 - Permission denied)

所以解决办法是在里面加上新的datadir目录。

root@huayuan:/var/lib# vim /etc/apparmor.d/usr.sbin.mysqld # vim:syntax=apparmor# Last Modified: Tue Jun 19 17:37:30 2007#include <tunables/global>/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,  /run/mysqld/mysqld.pid rw,  /run/mysqld/mysqld.sock w,  /sys/devices/system/cpu/ r,  #.........这里面写新的datadir目录，写2行，一行r，一行rwk。  /data3/mysql/ r,  /data3/mysql/** rwk,  # Site-specific additions and overrides. See local/README for details.  #include <local/usr.sbin.mysqld>}

然后重启mysql实例，ok，问题解决。