mariadb运行不起来

问题来了，执行 systemctl start mariadb.service后，mariadb服务一直起不来

执行journalctl -xe 查看启动日志，发现
```
[root@lancoo1 ~]# systemctl status mariadb.service

● mariadb.service - MariaDB 10.1 database server

Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)

Active: failed (Result: exit-code) since Tue 2017-11-07 15:41:32 CST; 10s ago

Process: 4150 ExecStopPost=/usr/libexec/mysql-wait-stop (code=exited, status=0/SUCCESS)

Process: 4134 ExecStart=/usr/libexec/mysqld --basedir=/usr $MYSQLD_OPTS $_WSREP_NEW_CLUSTER (code=exited, status=1/FAILURE)

Process: 4097 ExecStartPre=/usr/libexec/mysql-prepare-db-dir %n (code=exited, status=0/SUCCESS)

Process: 4074 ExecStartPre=/usr/libexec/mysql-check-socket (code=exited, status=0/SUCCESS)

Main PID: 4134 (code=exited, status=1/FAILURE)

Status: "MariaDB server is down"

Nov 07 15:41:32 lancoo1 systemd[1]: Starting MariaDB 10.1 database server...

Nov 07 15:41:32 lancoo1 mysql-prepare-db-dir[4097]: Database MariaDB is probably initialized in /var/lib/mysql already, nothing is done.

Nov 07 15:41:32 lancoo1 mysql-prepare-db-dir[4097]: If this is not the case, make sure the /var/lib/mysql is empty before running mysql-prepare-db-dir.

Nov 07 15:41:32 lancoo1 mysqld[4134]: 2017-11-07 15:41:32 140737353783488 [Note] /usr/libexec/mysqld (mysqld 10.1.20-MariaDB) starting as process 4134 ...

Nov 07 15:41:32 lancoo1 systemd[1]: mariadb.service: main process exited, code=exited, status=1/FAILURE

Nov 07 15:41:32 lancoo1 systemd[1]: Failed to start MariaDB 10.1 database server.

Nov 07 15:41:32 lancoo1 systemd[1]: Unit mariadb.service entered failed state.

Nov 07 15:41:32 lancoo1 systemd[1]: mariadb.service failed.
```

上述错误日志表明 mysql 数据库都还没有建立好 所以服务起不来，这根单独 的mysql服务有区别

问题： chown: changing ownership of '/var/lib/mysql': Operation not permitted

failed to start mariadb 10.1 database server

1： 发现是权限不够，首先检查防火墙是否开启，发现防火墙没有开

2：删除原先mysql相关的服务 进程 配置文件
 ```

[root@lancoo1 ~]# rm -rf /etc/my.cnf

[root@lancoo1 ~]# rm -rf /var/lib/mysql/*

[root@lancoo1 ~]# rpm -qa |grep mysql 
```

准备工作 
```

[root@lancoo1 ~]# chown -R  mysql:mysql  /var/lib/mysql

// 先初始化数据库
[root@lancoo1 ~]# sudo mysql_install_db --datadir=/home/mysql --user=root --defaults-file=/etc/my.cnf.d/openstack.cnf

// 启动服务

[root@lancoo1 ~]# systemctl start mariadb

//查看状态

[root@lancoo1 ~]# systemctl status mariadb.service
```