安装包下载
访问http://dev.mysql.com/downloads/mysql/，找到MySQL Community Server下载页面，平台选择“Red Hat Enterprise Linux 7/ Oracle Linux”，然后选择64位的bundle整合包下载,mysql-5.7.17.tar
准备工作
1）安装依赖包：
# yum -y install perl-Data-Dumper perl-JSON perl-Time-HiRes
2）停止mariadb服务
#systemctl stop mariadb
3）删除数据
#rm -rf /var/lib/mysql/*
4）卸载软件包
# rpm -e --nodeps mariadb-server mariadb
# rpm -qa |grep mysql
mysql-community-client-5.7.17-1.el7.x86_64 mysql-community-minimal-debuginfo-5.7.17-1.el7.x86_64
mysql-community-test-5.7.17-1.el7.x86_64 mysql-community-common-5.7.17-1.el7.x86_64
mysql-community-devel-5.7.17-1.el7.x86_64 mysql-community-libs-compat-5.7.17-1.el7.x86_64
mysql-community-libs-5.7.17-1.el7.x86_64 mysql-community-embedded-5.7.17-1.el7.x86_64
mysql-community-embedded-compat-5.7.17-1.el7.x86_64 mysql-community-embedded-devel-5.7.17-1.el7.x86_64
mysql-community-server-5.7.17-1.el7.x86_64
# ls /etc/my.cnf
/etc/my.cnf
# ls /var/log/mysqld.log
/var/log/mysqld.log
# ls /var/lib/mysql
# grep mysql /etc/passwd
mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin
启动mysql服务
# systemctl start mysqld
# systemctl enable mysqld
# systemctl status mysqld
# grep 'temporary password' /var/log/mysqld.log
2019-07-19T11:49:14.026897Z 1 [Note] A temporary password is generated for root@localhost: a3kKn4fdM-Fu
# mysql -u root -p'a3kKn4fdM-Fu'
mysql> alter user root@localhost identified by '123qqq...A'； //修改初始密码
Mysql主从配置
准备工作：
# systemctl stop firewalld
# systemctl disable firewalld
# vim /etc/sysconfig/selinux //disable selinux
主服务器操作：
1）修改/etc/my.cnf配置，启用bin-log
[mysqld]
log_bin=master43 //启用binlog日志，并指定文件名前缀
server_id=43 //指定服务器ID号
# systemctl restart mysqld.service
2）新建一个备份用户，授予复制权限，需要的权限为REPLICATION SLAVE，允许其从Slave服务器访问
mysql> grant replication slave on *.*
-> to 'replicater'@'10.236.110.%'
-> identified by '123qqq...A';
3）修改/etc/my.cnf配置，配置从服务器
[mysqld]
log_bin=master44
server_id=44
# systemctl restart mysqld.service
4）通过CHANGE MASTER语句指定MASTER服务器的IP地址、同步用户名/密码、起始日志文件、偏移位置（参考MASTER上的状态输出show master status）
mysql> change master to master_host='10.236.110.43'，
-> master_user='replicater',
-> master_password='123qqq...A',
-> master_log_file='master43.000001',
-> master_log_pos=454;
5）开启slave
mysql> start slave；
mysql> show slave status\G;
...
Slave_IO_Running: Yes //IO线程应该已运行
Slave_SQL_Running: Yes //SQL线程应该已运行
...
若START SLAVE直接报错失败，请检查CHANGE MASTER相关设置是否有误，纠正后再重试；若IO线程或SQL线程有一个为“No”，则应检查服务器的错误日志，分析并排除故障后重启主从复制
配置半同步复制
1）查看是否允许动态加载模块默认允许
mysql> show variables like 'have_dynamic_loading';
have_dynamic_loading | YES
2）命令行加载插件，用户需有SUPER权限（主从库上操作）
mysql> INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so';
mysql> INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so';
3）查看系统库下的表，模块是否安装成功：
mysql> SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE '%semi%';
rpl_semi_sync_master | ACTIVE
rpl_semi_sync_slave | ACTIVE
高可用架构下，master和slave需同时启动，以便在切换后能继续使用半同步复制
# vim /etc/my.cnf
[mysqld]
plugin-load="rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so"
rpl-semi-sync-master-enabled = 1
rpl-semi-sync-slave-enabled = 1
