root等賬號密碼的丟失，影響是致命的。下面給出方法，無密碼登錄mysql，修改密碼。
以下為5.7版本root賬號的密碼修改方法，5.6版本類似。
1.發現密碼忘記了，無法登錄數據庫
[root@192-168-199-198 /]# /opt/mysql5.7/bin/mysql -uroot -pfander -h127.0.0.1 -P3307
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'root'@'127.0.0.1' (using password: YES)
2.關閉數據庫
我這里用service關閉。沒有service，就只能kill掉了。
[root@192-168-199-198 init.d]# service mysql3307 stop
Shutting down MySQL(mysql3307)............ SUCCESS!
3.加跳過權限表參數，重啟數據庫
這樣不輸入密碼，也能進入數據庫了。
## 臨時加--skip-grant-tables參數啟動，跳過權限表
/opt/mysql5.7/bin/mysqld --defaults-file=/data/mysql/mysql3307/my.cnf --skip-grant-tables &
#無密碼登錄db
/opt/mysql5.7/bin/mysql -S /tmp/mysql3307.sock
4.設置新密碼
MySQL5.7后password字段用authentication_string字段代替了。
use mysql;
update user set authentication_string=password('fander') where user='root' and host='%';
flush privileges;
5.去掉跳過權限表參數，重啟數據庫
#重啟數據庫
[root@192-168-199-198 init.d]# service mysql3307 restart
Shutting down MySQL(mysql3307)............ SUCCESS!
Starting MySQL(mysql3307). SUCCESS!
[1]+ Done /opt/mysql5.7/bin/mysqld --defaults-file=/data/mysql/mysql3307/my.cnf --skip-grant-tables
#登錄已無問題
[root@192-168-199-198 init.d]# /opt/mysql5.7/bin/mysql -uroot -pfander -h127.0.0.1 -P3307
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 22
Server version: 5.7.23-log MySQL Community Server (GPL)
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