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前几天晚上把阿里云服务器整个磁盘重置了，里面本来东西也不多，就自己平时测试用一下而已。之前不重视安全问题，就因为上面啥东。，后来发现老是被人暴力尝试root密码，虽然我没有开放ssh root用户登录，但是感觉还是会有风险，重置系统后就把ssh默认的端口号改了，还装了tripwire文件系统检测软件，以及fail2ban用来防止ssh暴力**。
阿里云centos默认的是7.3，几个月前第一次装的时候没有更新系统就装MySQL，用rpm命令装特麻烦，要解决各种依赖，还要把自带的mariaDB-libs 先删掉才能装，安装好之后还无法启动，各种报错，后来重装了一两次才搞定了。 这一次先把系统升级到了centos7.5 ， 一开始还配置了mysql 在线yum源，可是通过在线yum源下载实在是太慢，几k每秒，后来直接把下载好的rpm包配置好本地yum源，然后直接yum安装，特别轻松，一次搞定，启动也没问题，以下是详细步骤：
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从mysql官网下载安装包，mysql-5.7.23-1.el7.x86_64.rpm-bundle.tar，再传到Linux服务器或者直接wget下载下来
解档放到 /usr/local/yum/mysqlRPMs 下
1.执行createrepo /usr/local/yum 命令之后，会在该目录下产生yum源元数据，
2.再去到 /etc/yum.repos.d/ 目录下添加一个后缀为repo的文件，取名为mysql-local.repo, 内容为
#the RPMs of MySQL server
[mysql-local]
name=mysql-local
baseurl=file:///usr/local/yum
gpgcheck=0
enabled=1
如此这般本地yum源就配置好了
[[email protected] ~]# createrepo /usr/local/yum
Spawning worker 0 with 3 pkgs
Spawning worker 1 with 3 pkgs
Spawning worker 2 with 3 pkgs
Spawning worker 3 with 3 pkgs
Workers Finished
Saving Primary metadata
Saving file lists metadata
Saving other metadata
Generating sqlite DBs
Sqlite DBs complete
[[email protected] ~]# ls /usr/local/yum
mysqlRPMs repodata[[email protected] ~]# vim /etc/yum.repos.d/mysql-local.repo [[email protected] ~]# yum list|grep mysql-local
mysql-community-client.x86_64 5.7.23-1.el7 mysql-local
mysql-community-common.x86_64 5.7.23-1.el7 mysql-local
mysql-community-devel.x86_64 5.7.23-1.el7 mysql-local
mysql-community-embedded.x86_64 5.7.23-1.el7 mysql-local
mysql-community-embedded-compat.x86_64 5.7.23-1.el7 mysql-local
mysql-community-embedded-devel.x86_64 5.7.23-1.el7 mysql-local
mysql-community-libs.x86_64 5.7.23-1.el7 mysql-local
mysql-community-libs-compat.x86_64 5.7.23-1.el7 mysql-local
mysql-community-minimal-debuginfo.x86_64 5.7.23-1.el7 mysql-local
mysql-community-server.x86_64 5.7.23-1.el7 mysql-local
mysql-community-server-minimal.x86_64 5.7.23-1.el7 mysql-local
mysql-community-test.x86_64 5.7.23-1.el7 mysql-local接下来就可以执行命令yum install mysql-community-server 进行安装了，期间会自动替换mariadb-libs库文件，如下图。
若是用rpm命令安装，要手动先把mariadb-libs删掉，才能安装mysql，还要按顺序一步步解决依赖性问题，特麻烦，我第一次装的时候就是用rpm，超级麻烦！还是yum好用啊。
这样MySQL就安装好了，接下来进行简单的配置。
首先执行命令 mysqld --initialize --user=mysql --console 进行初始化，之后可以从log中获取初始密码
[[email protected] ~]# mysqld --initialize --user=mysql --console
[[email protected] ~]# grep password /var/log/mysqld.log
2018-10-23T00:21:48.595001Z 1 [Note] A temporary password is generated for [email protected]: >sax;A?sK6Mc通过mysql -uroot -p 输入上面默认密码登陆上去
修改/etc/my.cnf 配置文件，主要是修改默认字符为utf-8，不然数据库表无法正常插入中文，可以用show variables like 'character%'; 来看看默认的字符编码。 结果提示必须修改密码， 应该是初始密码过期了（默认只有360秒的有效期），那就用ALTER USER user() INDENTIFIED BY '新密码' 来改密码吧，之后再查看一下默认编码，value为latin1的那两个都要改成utf8
mysql> show variables like 'character%';
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> ALTER USER user() IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
执行命令 vim /etc/my.cnf 添加以下两项
[client]
port=3306
default-character-set=utf8
[mysql]
default-character-set=utf8
并在[mysqld]下追加
collation-server=utf8_general_ci
character_set_server=utf8
如图： 保存并重启mysqld服务 sytemctl restart mysqld ， 再执行show variables like 'character%';去查询字符集编码，就改成了utf8了。
mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)mysql 默认不允许远程登陆的，所以即便防火墙添加了3306端口，或者关闭防火墙，telnet ip 3306都是不通的。需要修改mysql.user 用户表的host字段，把值localhost 改成%即可。
mysql> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select user,host from user;
+---------------+-----------+
| user | host |
+---------------+-----------+
| mysql.session | localhost |
| mysql.sys | localhost |
| root | localhost |
+---------------+-----------+
3 rows in set (0.00 sec)
mysql> update user set host = '%' where user ='root';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select user,host from user;
+---------------+-----------+
| user | host |
+---------------+-----------+
| root | % |
| mysql.session | localhost |
| mysql.sys | localhost |
+---------------+-----------+
3 rows in set (0.00 sec)至此，mysql 5.7 在centos7.5下最基本的安装与配置就完成了。
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补充：后来发现仅仅是修改上面的host字段还是不能远程访问，还是直接用授权法毕竟简单快捷。
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root' @'%' WITH GRANT OPTION;
Query OK, 0 rows affected (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)这样就没问题啦~~