在centos7上安装mysql 5.7

安装yum源

 yum install http://repo.mysql.com/mysql57-community-release-el7.rpm

检测老版本

rpm -qa | egrep "mariadb|mysql" #查看是系统否存在老版本的mysql

若有删掉

rpm -e mariadb* --nodeps

安装mysql57

yum install mysql-server -y #开始安装mysql

systemctl start mysqld

第一次安装的时候，

cat /var/log/mysqld.log | grep password

查看到默认密码

复制后，用默认密码登陆

然后第一次登陆后，用alter user 改密码,默认8位数以上，有大小写，有标点

alter user root@localhost identified by 'xxxxxxxxx';

查看密码等级

show variables like 'validate_password%';

然后修改密码等级，

set global validate_password_policy  = 0;

//只是检测密码位数，LOW，不在限制大小混等

初始化安全向导

mysql_secure_installation

 -------------------------------------------------------------------------------------------------

 如果碰到performance_schema.session_variables 不存在，

performance_schema在mysql5.5以上就有自带

performance_schema（安装数据库时自带的）如果装数据库或者使用数据时不小心删除了，就会出现Table‘performance_schema.session_variables’ doesn’t exist的异常。

解决方式：

第一步：

# mysql_upgrade -uroot -p

第二步：

# systemctl stop mysqld
# systemctl start mysqld

 -----------------------------------------------------------

然后加入自启动

systemctl enable mysqld

systemctl restart mysql

进入后 用status查看版本状态等。

修改vim /etc/my.cnf

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html

[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
character-set-server=utf8 
collation-server=utf8_general_ci 
performance_schema_max_table_instances=400 
table_definition_cache=400 
table_open_cache=256
wait_timeout=5184000            
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

#default-character-set=utf8   这句话在5.6上没报错，但在5.7版本，报错。需要注释掉。

[mysql.server]
default-character-set=utf8


[mysqld_safe]
default-character-set = utf8


[client]
default-character-set = utf8

show global variables like 'wait_timeout';

show variables like 'character%';