mysql: Character set 'utf8mb4' is not a compiled character set and is not specified in the '/usr/sha

1.场景：由于之前mysql中一起使用utf8编码，最近由于emoji表情的原因，需要使用utf8mb4编码

操作如下：

修改配置文件/etc/my.cnf：

[client]
default-character-set=utf8mb4

[mysqld]
character-set-client-handshake=FALSE
character-set-server=utf8mb4
collation_server=utf8mb4_unicode_ci

[mysql]
default-character-set=utf8mb4

2.错误信息：

修改配置文件成功后，重启动数据库，但是重启动成功后，登录时出现如下错误信息，并直接退出

[mysql@localhost data1]$ mysql -p -S mysqldata1/sock/mysql.sock 
mysql: Character set 'utf8mb4' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file

3.参考资料：

https://dev.mysql.com/doc/refman/5.5/en/charset-configuration.html

https://github.com/brianmario/mysql2/issues/367

4.实施方法：

把配置文件/usr/share/mysql/charsets/Index.xml中的utf8编码改为utf8mb4即可，修改方法如下：
[修改前：]
<charset name="utf8">
  <family>Unicode</family>
  <description>UTF-8 Unicode</description>
  <alias>utf-8</alias>
  <collation name="utf8_general_ci"     id="33">
   <flag>primary</flag>
   <flag>compiled</flag>
  </collation>
  <collation name="utf8_bin"            id="83">
    <flag>binary</flag>
    <flag>compiled</flag>
  </collation>
</charset>


[修改后：]
<charset name="utf8mb4">
  <family>Unicode</family>
  <description>UTF-8 Unicode</description>
  <alias>utf-8</alias>
  <collation name="utf8_general_ci"     id="33">
   <flag>primary</flag>
   <flag>compiled</flag>
  </collation>
  <collation name="utf8_bin"            id="83">
    <flag>binary</flag>
    <flag>compiled</flag>
  </collation>
</charset>