阿里云ECS 安装了mysql 5.6，使用 systemctl start mysql成功启动mysql，可使用 systemctl enable mysql将mysql加入到开机自启动，可却报错：
[root@go ~]# mysql -V
mysql Ver 14.14 Distrib 5.6.29, for Linux (x86_64) using EditLine wrapper
[root@go ~]#
[root@go ~]# systemctl enable mysql
Failed to execute operation: No such file or directory
[root@go ~]# systemctl enable mariadb
Failed to execute operation: No such file or directory
[root@go ~]#
使用systemctl enable mariadb 也是一样的，我在Linode中的centos7是直接使用 systemctl enable mariadb 加入自启动的
但是运行 systemctl enable httpd 是没有报错。
[root@go ~]# chkconfig
Note: This output shows SysV services only and does not include native
systemd services. SysV configuration data might be overridden by native
systemd configuration.
If you want to list systemd services use 'systemctl list-unit-files'.
To see services enabled on particular target use
'systemctl list-dependencies [target]'.
aegis 0:off 1:off 2:on 3:on 4:on 5:on 6:off
agentwatch 0:off 1:off 2:on 3:on 4:on 5:on 6:off
netconsole 0:off 1:off 2:off 3:off 4:off 5:off 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
[root@go ~]#systemctl enable mysqld
systemctl list-unit-files 查看下有没有mysql.service 文件
systemctl enable mysqld.service