service mysqld restart 失败

用的是mysql5.5
centos 7

然后配置完主从之后想重启mysql 但是出错了 提示
Redirecting to /bin/systemctl restart mysqld.service
Failed to restart mysqld.service: Unit not found
但是使用如下也不行
systemctl restart mysqld.service
systemctl start mysqld.service
systemctl stop mysqld.service
怎么解决呢

本地服务重启一下呢,他显示是找不到服务