老高最近又迁移了一次数据库，期间遇到了很多问题，本文主要记录了如果备份数据库并恢复到新的数据库中！

ps. 由于老高工作用的是PG数据库，而博客用的是MySQL，于是本篇就把二者的用法都写出来吧！

备份数据库

备份数据库就是把当前的数据库的指定数据导出为一种固定的格式，相当于给当前的数据做了一次快照。

MySQL

PG

一些问题

MySQL 8.0 默认打开了log_bin，导致/var/lib/mysql/下binlog文件太大，如何关闭呢？

systemctl set-environment MYSQLD_OPTS="--disable-log-bin"
# 要是想重新打开，执行unset命令即可
systemctl unset-environment MYSQLD_OPTS

小技巧

如果你忘记了MySQL的root用户密码，可以执行下面的操作，进行密码重置

1. Stop mysql:
systemctl stop mysqld

2. Set the mySQL environment option 
systemctl set-environment MYSQLD_OPTS="--skip-grant-tables"

3. Start mysql usig the options you just set
systemctl start mysqld

4. Login as root
mysql -u root

5. Update the root user password with these mysql commands
mysql> UPDATE mysql.user SET authentication_string = PASSWORD('MyNewPassword')
    -> WHERE User = 'root' AND Host = 'localhost';
mysql> FLUSH PRIVILEGES;
mysql> quit

6. Stop mysql
systemctl stop mysqld

7. Unset the mySQL envitroment option so it starts normally next time
systemctl unset-environment MYSQLD_OPTS

8. Start mysql normally:
systemctl start mysqld

Try to login using your new password:
7. mysql -u root -p

修复数据库

mysqlcheck --auto-repair -A -u username -ppassword

Refers: