一、系统环境

 [root@localhost home]# cat /etc/redhat-release

 CentOS Linux release 7.2.1511 (Core)

二、mysql安装

安装mysql和mysql-devel都成功，但是安装mysql-server失败，如下：

[root@localhost home]# yum install mysql-server
 已加载插件：fastestmirror, langpacks
 Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
 base | 3.6 kB 00:00:00 
 extras | 3.4 kB 00:00:00 
 updates | 3.4 kB 00:00:00 
 (1/4): base/7/x86_/group_gz | 155 kB 00:00:01 
 (2/4): extras/7/x86_/primary_db | 139 kB 00:00:01 
 (3/4): base/7/x86_/primary_db | 5.6 MB 00:00:38 
 (4/4): updates/7/x86_/primary_db | 4.7 MB 00:00:39 
 Loading mirror speeds from cached hostfile
 * base: mirrors.163.com
 * extras: mirrors.163.com
 * updates: mirrors.163.com
 没有可用软件包 mysql-server。
 错误：无须任何处理

出现这样问题是CentOS 7 版本将MySQL数据库软件从默认的程序列表中移除，用mariadb代替了

有两种解决办法：

方法一：安装mariadb

MariaDB数据库管理系统是MySQL的一个分支，采用GPL授权许可 MariaDB的目的是完全兼容MySQL，包括API和命令行，使之能轻松成为MySQL的代替品。MariaDB由MySQL的创始人Michael Widenius（英语：Michael Widenius）主导开发，他早前将自己创建的公司MySQL AB卖给了SUN，此后，随着SUN被甲骨文收购，MySQL的所有权也落入Oracle的手中。MariaDB名称来自Michael Widenius的女儿Maria的名字。

安装mariadb，输入安装命令

[root@localhost home]# yum install mariadb-server mariadb

mariadb数据库的相关命令是：

 systemctl start mariadb #启动MariaDB
 systemctl stop mariadb #停止MariaDB
 systemctl restart mariadb #重启MariaDB
 systemctl enable mariadb #设置开机启动

先启动数据库

  [root@yl-web yl]# systemctl start mariadb

默认无密码

[root@localhost lzh]# mysql -u root -p
Enter password: 
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 6
Server version: 5.5.52-MariaDB MariaDB Server

Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.01 sec)

方法二：官网下载安装mysql-server

# wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
# rpm -ivh mysql-community-release-el7-5.noarch.rpm
# yum install mysql-community-server

安装成功后重启mysql服务

    # service mysqld restart

初次安装mysql，root账户没有密码

[root@localhost lzh]# 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 |
+--------------------+
4 rows in set (0.01 sec)

设置密码

mysql> set password for 'root'@'localhost' =password('password');
Query OK, 0 rows affected (0.00 sec)

安装完以后mariadb自动就被替换了，将不再生效。

[root@localhost lzh]# rpm -qa |grep mariadb

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