linux服务器安装Mysql后，只能看到information_schema/test这两个库，无法修改密码，无法连接mysql数据库方法

修改mysql数据库密码
修改MySQL的登录设置：
vim /etc/my.cnf
在[mysqld]的段中加上一句：skip-grant-tables
例如：
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-grant-tables
保存并且退出vi。

3．重新启动mysqld
service mysqld restart
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
或者出现：
Redirecting to /bin/systemctl restart mysqld.service

4．登录并修改MySQL的root密码
mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3 to server version: 3.23.56
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.
mysql> USE mysql ;
Database changed
mysql>UPDATE mysql.user SET password=PASSWORD(‘test123’) WHERE User=‘root’;
（注意括号里单引号内的就是你要重新设置的密码）
Query OK, 0 rows affected (0.00 sec)
Rows matched: 5 Changed: 0 Warnings: 0
mysql> flush privileges ;
Query OK, 0 rows affected (0.01 sec)
mysql> quit
Bye

5．将MySQL的登录设置修改回来
vim /etc/my.cnf
将刚才在[mysqld]的段中加上的skip-grant-tables删除
保存并且退出vim
6．重新启动mysqld
service mysqld restart
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
或：
Redirecting to /bin/systemctl restart mysqld.service
7.检测新密码是否生效
输入mysql -u root -p 回车
然后输入新密码，回车，如下图修改成功

数据库远程连接出现Host is not allowed to connect to this MySQL server解决方法

先说说这个错误，其实就是我们的MySQL不允许远程登录，所以远程登录失败了，解决方法如下：
1.在装有MySQL的机器上登录MySQL mysql -u root -p密码
2.执行use mysql;
3.执行update user set host = ‘%’ where user = ‘root’;这一句执行完可能会报错，不用管它。
4.执行FLUSH PRIVILEGES;
5.经过上面4步，就可以解决这个问题了。
注: 第四步是刷新MySQL的权限相关表，一定不要忘了，我第一次的时候没有执行第四步，结果一直不成功，最后才找到这个原因。

linux服务器安装Mysql后，只能看到information_schema/test这两个库，无法修改密码

打开一个ssh连接，登录到mysql数据库
直接用命令mysql，进入数据库
修改mysql.user表

use mysql;

delete from user;

INSERT INTO user (Host, User, Password, Select_priv, Insert_priv, Update_priv, Delete_priv, Create_priv, Drop_priv, Reload_priv, Shutdown_priv, Process_priv, File_priv, Grant_priv, References_priv, Index_priv, Alter_priv, Show_db_priv, Super_priv, Create_tmp_table_priv, Lock_tables_priv, Execute_priv, Repl_slave_priv, Repl_client_priv, Create_view_priv, Show_view_priv, Create_routine_priv, Alter_routine_priv, Create_user_priv, Event_priv, Trigger_priv, Create_tablespace_priv, ssl_type, ssl_cipher, x509_issuer, x509_subject, max_questions, max_updates, max_connections, max_user_connections, plugin, authentication_string) VALUES
("%",“root”,"",“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,"","","","",0,0,0,0,"",""),
(“localhost”,"","",“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,“Y”,"","","","",0,0,0,0,"","");

4.重启mysql： service mysql restart

启动后登录mysql数据库，可以正常看到所有的数据库了。