Linux 下 MySQL Root 密碼修改與遺忘密碼急救全流程

場景一：已知舊密碼，常規修改

# 方法 1：mysqladmin (推腳本自動化)
/usr/local/mysql/bin/mysqladmin -u root -p'old_pass' password 'NewStrongPass2024!'

# 方法 2：SQL 登入後修改 (支援多 host)
mysql -u root -p
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'NewStrongPass2024!';
mysql> ALTER USER 'root'@'127.0.0.1' IDENTIFIED BY 'NewStrongPass2024!';
mysql> ALTER USER 'root'@'%' IDENTIFIED BY 'NewStrongPass2024!';  -- 謹慎開放遠程
mysql> FLUSH PRIVILEGES;

場景二：遺忘 Root 密碼 — 跳過授權表啟動急救

1. 停止服務：systemctl stop mysqld 或 killall mysqld
2. 跳過授權啟動：

   # 臨時配置文件法 (推薦，不污染主配置)
   cat > /tmp/mysqld_safe.cnf <<'EOF'
   [mysqld]
   skip-grant-tables
   skip-networking  -- 僅本地 Socket，防外部趁虛而入
   EOF
   
   /usr/local/mysql/bin/mysqld_safe --defaults-file=/tmp/mysqld_safe.cnf &
   

3. 無密碼登入修改：

   
   mysql -u root
   mysql> FLUSH PRIVILEGES;  -- 5.7+ 必須先執行
   mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'NewStrongPass2024!';
   mysql> FLUSH PRIVILEGES;
   

4. 恢復正常啟動：

   
   killall mysqld
   systemctl start mysqld
   mysql -u root -p'NewStrongPass2024!'
   

關鍵細節避坑

安全加固清單 (修改密碼後必做)

mysql> DELETE FROM mysql.user WHERE User='';           -- 刪除匿名用戶
mysql> DELETE FROM mysql.user WHERE User='root' AND Host NOT IN ('localhost','127.0.0.1','::1');
mysql> DROP DATABASE IF EXISTS test;
mysql> DELETE FROM mysql.db WHERE Db='test' OR Db='test\\_%';
mysql> FLUSH PRIVILEGES;

總結

「知舊改舊、忘舊跳過授權、改畢強權限」三步走。生產環境建議配合 mysql_secure_installation 腳本一鍵完成上述加固，並定期輪換密碼、審計遠程賬號。