1.卸载Mariadb
查询所安装的MariaDB组件：
[root@localhost logs]# rpm -qa | grep Maria*
MariaDB-server-5.5.49-1.el7.centos.x86_64
MariaDB-common-5.5.49-1.el7.centos.x86_64
MariaDB-client-5.5.49-1.el7.centos.x86_64
卸载数据库：
[root@localhost logs]# yum -y remove maria*
删除数据库文件：（如果存在则删除，不存在就算了）
[root@localhost logs]# rm -rf /var/lib/mysql/*
[root@localhost logs]# rm -f /etc/my.cnf
[root@localhost logs]# rm -rf /var/lib/mysql/
2.安装mysql
mysql-devel可以用yum源安装：
[root@localhost logs]#yum install mysql-devel
mysql-server和mysql-client不能用yum源，yum源只有MariaDB：
[root@localhost logs]# wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
[root@localhost logs]# rpm -ivh mysql-community-release-el7-5.noarch.rpm
[root@localhost logs]# yum install mysql-community-server
安装成功后重启mysql服务。
[root@localhost logs]# service mysqld restart
或者：
[root@localhost logs]# systemctl restart mysqld.service
初次安装mysql，root账户没有密码。
[root@yl-web yl]# mysql -u root
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.26 MySQL Community Server (GPL)
Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
rows in set (0.01 sec)
mysql>
设置密码
mysql> set password for 'root'@'localhost' = password('root');
Query OK, 0 rows affected (0.00 sec)
mysql>
不需要重启数据库即可生效。
在mysql安装过程中如下内容：
Installed:
mysql-community-client.x86_64 0:5.6.26-2.el7 mysql-community-devel.x86_64 0:5.6.26-2.el7
mysql-community-libs.x86_64 0:5.6.26-2.el7 mysql-community-server.x86_64 0:5.6.26-2.el7
Dependency Installed:
mysql-community-common.x86_64 0:5.6.26-2.el7
Replaced:
mariadb.x86_64 1:5.5.41-2.el7_0 mariadb-devel.x86_64 1:5.5.41-2.el7_0 mariadb-libs.x86_64 1:5.5.41-2.el7_0
mariadb-server.x86_64 1:5.5.41-2.el7_0
所以安装完以后mariadb自动就被替换了，将不再生效。
[root@yl-web yl]# rpm -qa |grep mariadb
[root@yl-web yl]#
三、配置mysql
1、编码
mysql配置文件为/etc/my.cnf
最后加上编码配置
[mysql]
default-character-set =utf8
这里的字符编码必须和/usr/share/mysql/charsets/Index.xml中一致。
2、远程连接设置
把在所有数据库的所有表的所有权限赋值给位于所有IP地址的root用户。
mysql> grant all privileges on *.* to root@'%' identified by 'root';
如果是新用户而不是root，则要先新建用户
mysql>create user 'username'@'%' identified by 'password';
3.如果是阿里云，需要开启安全组开放3306端口的外网访问权限；并关闭防火墙，命令见《centos7 防火墙》
此时就可以进行远程连接了。
4.如果运行爬虫，会报too many connection错误，作以下设置：（详情见《解决Mysql错误Too many connections的方法》）
vim /etc/my.conf
在[mysqld]下添加：
max_connections=1000
wait_timeout=100
interactive_timeout=100
max_allowed_packet=15M
show processlist;
show variables like "max_connections";
show global variables like 'wait_timeout';
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