估计是升级了 MySQL 的软件包，管理数据库的某些表结构发生了变化，所以还需要升级数据库的相关表

修复

执行：mysql_upgrade -u root -p
然后根据提示输入 mysql 的 root 帐户密码，修复过程就可自动运行。此时会有如下形式的提示信息输出：

屏幕输出

mysql_upgrade -u root -p
 Enter password:
 Looking for 'mysql' as: mysql
 Looking for 'mysqlcheck' as: mysqlcheck
 Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/lib/mysql/mysql.sock'
 Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/lib/mysql/mysql.sock'
 wp_commentmeta                               OK
 wp_comments                                  OK
 wp_links                                     OK
 wp_options                                   OK
 wp_postmeta                                  OK
 wp_posts                                     OK
 wp_term_relationships                        OK
 wp_term_taxonomy                             OK
 wp_terms                                     OK
 wp_usermeta                                  OK
 wp_users                                     OK
 mysql.columns_priv                                 OK
 mysql.db                                           OK
 mysql.event                                        OK
 mysql.func                                         OK
 mysql.general_log                                  OK
 mysql.help_category                                OK
 mysql.help_keyword                                 OK
 mysql.help_relation                                OK
 mysql.help_topic                                   OK
 mysql.host                                         OK
 mysql.ndb_binlog_index                             OK
 mysql.plugin                                       OK
 mysql.proc                                         OK
 mysql.procs_priv                                   OK
 mysql.servers                                      OK
 mysql.slow_log                                     OK
 mysql.tables_priv                                  OK
 mysql.time_zone                                    OK
 mysql.time_zone_leap_second                        OK
 mysql.time_zone_name                               OK
 mysql.time_zone_transition                         OK
 mysql.time_zone_transition_type                    OK
 mysql.user                                         OK
 Running 'mysql_fix_privilege_tables'...      OK

 执行完，会出现一堆OK，就可以了
看来每次在 Linux 中升级了 MySQL 软件包之后都需要进行类似的数据库升级操作。