一、场景：最近想搞mysql主从复制，需要在两台服务器上安装mysql，之前有一台已经装好了mysql5.7.21，于是在另外一台上也装mysql5.7.21，安装过程中碰到了蛮多坑，因此记录下来。

二、下载安装命令见下：

1. wget https://dev.mysql.com//Downloads/MySQL-5.7/mysql-5.7.21-linux-glibc2.12-x86_64.tar.gz
2. tar -zxvf mysql-5.7.21-linux-glibc2.12-x86_64.tar.gz

我将解压后文件夹所有文件复制到/usr/local/mysql下

3. sudo cp -r mysql-5.7.21-linux-glibc2.12-x86_64/. /usr/local/mysql

在mysql文件夹下创建data文件夹(mysql的数据文件夹)和mysql_3306.err日志文件

4. sudo mkdir /usr/local/mysql/data
5. sudo vim mysql_3306.err
6. sudo chmod -R 777 ./ #设置读写权限

添加用户组

7. sudo groupadd mysql

添加用户

8. sudo useradd -r -g mysql -s /bin/false mysql

添加mysql配置信息

9. sudo /etc/my.cnf
   添加信息如下：
   [client]
   port = 3306
   socket = /usr/local/mysql/mysql.sock
   [mysql]
   no-auto-rehash

[mysqld]
socket = /usr/local/mysql/mysql.sock
character_set_server= utf8
init_connect= 'SET NAMES utf8'
basedir= /usr/local/mysql
datadir= /usr/local/mysql/data
socket = /usr/local/mysql/mysql.sock
pid-file= /usr/local/mysql/mysqld.pid
log-error= /usr/local/mysql/mysql_3306.err
sql_mode= STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

[mysqld_safe]
open-files-limit = 8192
log-error= /usr/local/mysql/mysql_3306.err
保存后对mysql初始化

10. sudo /usr/local/mysql/bin/mysqld --initialize --user=mysql --basedir=/usr/local/mysql/bin/mysqld --datadir=/usr/local/mysql/data
    如果报错，可以去/usr/local/mysql/mysql_3306.err文件查看error
    初始化密码可以看到，如：
    [Note] A temporary password is generated for root@localhost: *.>9Yy9Uk&Fx

启动在后台

11. sudo /usr/local/mysql/bin/mysqld_safe --user=mysql &

修改密码

12. sudo /usr/local/mysql/bin/mysql -u root -p
    密码见10，如果报错，则修改/etc/my.cnf文件，在mysqld下面添加一行：
    skip-grant-tables

12成功后会进入mysql命令模式

13. use mysql; 一定要加分号
14. update mysql.user set authentication_string=password('你的密码') where user='root' ;
15. flush privileges;
16. quit 退出

注：启动：/usr/local/mysql/support-files/mysql.server start
自启动：sudo cp /usr/local/mysql/support-files/mysql.server /etc/init.d/mysql.server
若出现Navicat连接报错Host not allowed,
进入use mysql;
update user set host = '%' where user ='root';
flush privileges;