附上错误日志：

2015-06-23 22:39:06 1252 [Note] Giving 0 client threads a chance to die gracefully
2015-06-23 22:39:06 1252 [Note] Shutting down slave threads
2015-06-23 22:39:06 1252 [Note] Forcefully disconnecting 0 remaining clients
2015-06-23 22:39:06 1252 [Note] Binlog end
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'partition'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'BLACKHOLE'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'PERFORMANCE_SCHEMA'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_DATAFILES'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_TABLESPACES'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_FOREIGN_COLS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_FOREIGN'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_FIELDS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_COLUMNS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_INDEXES'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_TABLESTATS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_SYS_TABLES'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_INDEX_TABLE'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_INDEX_CACHE'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_CONFIG'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_BEING_DELETED'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_DELETED'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_FT_DEFAULT_STOPWORD'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_METRICS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_BUFFER_POOL_STATS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_BUFFER_PAGE_LRU'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_BUFFER_PAGE'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMP_PER_INDEX_RESET'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMP_PER_INDEX'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMPMEM_RESET'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMPMEM'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMP_RESET'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_CMP'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_LOCK_WAITS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_LOCKS'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'INNODB_TRX'
2015-06-23 22:39:09 1252 [Note] Shutting down plugin 'InnoDB'
2015-06-23 22:39:09 1252 [Note] InnoDB: FTS optimize thread exiting.
2015-06-23 22:39:09 1252 [Note] InnoDB: Starting shutdown...
2015-06-23 22:39:12 1252 [Note] InnoDB: Shutdown completed; log sequence number 448322
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'ARCHIVE'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'MyISAM'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'CSV'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'MRG_MYISAM'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'MEMORY'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'sha256_password'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'mysql_old_password'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'mysql_native_password'
2015-06-23 22:39:12 1252 [Note] Shutting down plugin 'binlog'
2015-06-23 22:39:12 1252 [Note] /usr/sbin/mysqld: Shutdown complete

150623 22:39:12 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
150623 22:39:39 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
2015-06-23 22:39:39 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2015-06-23 22:39:39 1190 [Warning] Buffered warning: Changed limits: max_open_files: 1024 (requested 5000)

2015-06-23 22:39:39 1190 [Warning] Buffered warning: Changed limits: table_cache: 431 (requested 2000)

2015-06-23 22:39:39 1190 [Note] Plugin 'FEDERATED' is disabled.
2015-06-23 22:39:39 1190 [Note] InnoDB: Using atomics to ref count buffer pool pages
2015-06-23 22:39:39 1190 [Note] InnoDB: The InnoDB memory heap is disabled
2015-06-23 22:39:39 1190 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2015-06-23 22:39:39 1190 [Note] InnoDB: Memory barrier is not used
2015-06-23 22:39:39 1190 [Note] InnoDB: Compressed tables use zlib 1.2.3
2015-06-23 22:39:39 1190 [Note] InnoDB: Using Linux native AIO
2015-06-23 22:39:39 1190 [Note] InnoDB: Not using CPU crc32 instructions
2015-06-23 22:39:39 1190 [Note] InnoDB: Initializing buffer pool, size = 1.0G
2015-06-23 22:39:40 1190 [Note] InnoDB: Completed initialization of buffer pool
2015-06-23 22:39:40 1190 [Note] InnoDB: Highest supported file format is Barracuda.
2015-06-23 22:39:40 1190 [Note] InnoDB: 128 rollback segment(s) are active.
2015-06-23 22:39:40 1190 [Note] InnoDB: Waiting for purge to start
2015-06-23 22:39:40 1190 [Note] InnoDB: 5.6.22 started; log sequence number 448322
2015-06-23 22:39:41 1190 [Note] Server hostname (bind-address): '*'; port: 3306
2015-06-23 22:39:41 1190 [Note] IPv6 is available.
2015-06-23 22:39:41 1190 [Note] - '::' resolves to '::';
2015-06-23 22:39:41 1190 [Note] Server socket created on IP: '::'.
2015-06-23 22:39:41 1190 [ERROR] Incorrect definition of table mysql.db: expected column 'User' at position 2 to have type char(16), found type char(80).
2015-06-23 22:39:41 1190 [ERROR] Incorrect definition of table mysql.event: expected column 'definer' at position 3 to have type char(77), found type char(141).
2015-06-23 22:39:41 1190 [ERROR] Incorrect definition of table mysql.event: expected column 'sql_mode' at position 14 to have type set('REAL_AS_FLOAT','PIPES_AS_CONCAT','ANSI_QUOTES','IGNORE_SPACE','NOT_USED','ONLY_FULL_GROUP_BY','NO_UNSIGNED_SUBTRACTION','NO_DIR_IN_CREATE','POSTGRESQL','ORACLE','MSSQL','DB2','MAXDB','NO_KEY_OPTIONS','NO_TABLE_OPTIONS','NO_FIELD_OPTIONS','MYSQL323','MYSQL40','ANSI','NO_AUTO_VALUE_ON_ZERO','NO_BACKSLASH_ESCAPES','STRICT_TRANS_TABLES','STRICT_ALL_TABLES','NO_ZERO_IN_DATE','NO_ZERO_DATE','INVALID_DATES','ERROR_FOR_DIVISION_BY_ZERO','TRADITIONAL','NO_AUTO_CREATE_USER','HIGH_NOT_PRECEDENCE','NO_ENGINE_SUBSTITUTION','PAD_CHAR_TO_FULL_LENGTH'), found type set('REAL_AS_FLOAT','PIPES_AS_CONCAT','ANSI_QUOTES','IGNORE_SPACE','IGNORE_BAD_TABLE_OPTIONS','ONLY_FULL_GROUP_BY','NO_UNSIGNED_SUBTRACTION','NO_DIR_IN_CREATE','POSTGRESQL','ORACLE','MSSQL','DB2','MAXDB','NO_KEY_OPTIONS','NO_TABLE_OPTIONS','NO_FIELD_OPTIONS','MYSQL323','MYSQL40','ANSI','NO_AUTO_VALUE_ON_ZERO','NO_BACKSLASH_ESCAPES','STRICT_TRANS_TABLES','STRICT_A
2015-06-23 22:39:41 1190 [ERROR] Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
2015-06-23 22:39:41 1190 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.6.22' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Community Server (GPL)
2015-06-23 23:00:47 7f7038bc0700 InnoDB: Error: Column last_update in table "mysql"."innodb_table_stats" is INT UNSIGNED NOT NULL but should be BINARY(4) NOT NULL (type mismatch).
2015-06-23 23:00:47 7f7038bc0700 InnoDB: Error: Fetch of persistent statistics requested for table "moodle"."mdl_config" but the required system tables mysql.innodb_table_stats and mysql.innodb_index_stats are not present or have unexpected structure. Using transient stats instead.