Docker启动MySQL在log日志中发现报错unknown variable ‘default

问题： 前一天我将mysql配置好了，就关闭了，第二天重新启动mysql容器发现刚启动完，就停止掉了，很离谱！！！

解决方案： docker logs mysql 查看mysql日志，发现报错：
unknown variable ‘default_character_set=utf8’.

发现是配置文件的问题：
修改前配置文件是：

[mysqld]
skip-name-resolve
#default_character_set = utf8 //删掉此行
character_set_server=utf8
datadir=/var/lib/mysql
server-id=1000
[mysql]
default-character-set = utf8
[mysql.server]
default-character-set = utf8
[mysqld_safe]
default-character-set = utf8
[client]
default-character-set = utf8

修改后配置文件是：

[mysqld] 
skip-name-resolve
character_set_server=utf8
datadir=/var/lib/mysql
server-id=1000
[mysql] 
default-character-set = utf8
[mysql.server]
default-character-set = utf8
[mysqld_safe]
default-character-set = utf8
[client]
default-character-set = utf8