Centos7系统MySQL安装：

1. wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
2. rpm -ivh mysql-community-release-el7-5.noarch.rpm
3. yum install mysql-community-server
4. MySQL服务重启：service mysqld restart
5. 设置root用户名密码：
   mysql -u root
   mysql> set password for ‘root’@‘localhost’ = password(‘mypasswd’);
   mysql> exit
   6.MySQL版本查询：mysql --version
   7.修改字符集：
   查看当前 MySQL 字符集：mysql> show variables like ‘character%’;
   
   修改成utf8: vim /etc/my.cnf,添加如下配置：
   [mysqld]
   character_set_server = utf8
   [mysql]
   default-character-set = utf8
   重启MySQL:service mysqld restart
   重新查询：mysql> show variables like ‘character%’;
   
   8.用navicat远程连接Linux系统的MySQL:
   注意要关闭防火墙（centos7命令：systemctl stop firewalld.service
   mysql>GRANT ALL PRIVILEGES ON . TO ‘root’@’%’ IDENTIFIED BY ‘lwl980429’ WITH GRANT OPTION;
   mysql> flush privileges;
   格式：grant 权限 on 数据库.* to 用户名@登录主机 identified by “密码”;　
   mysql>grant all privileges on . to root@’%’ identified by ‘root’;
   mysql>flush privileges;
   

tar -zxvf命令详解：
x : 从 tar 包中把文件提取出来
z : 表示 tar 包是被 gzip 压缩过的，所以解压时需要用 gunzip 解压
v : 显示详细信息
f xxx.tar.gz : 指定被处理的文件是 xxx.tar.gz

Ubuntu设置允许root用户登录：
sudo passwd
vim /etc/ssh/sshd_config
找到 PermitRootLogin 这项 将其改为 yes
service ssh restart