如果使用 MySQL 数据库忘记了root账号密码，可以通过调节配置文件，跳过密码的方式登数据库，
在数据库里面修改账号密码，一般默认的账号是 root
1、编辑 MySQL 配置文件 my.cnf
注意： 以实际 my.cnf 配置文件路径为准
vim /etc/my.cnf
[mysqld]
spik-grant-tables #增加
2、重启 MySQL 服务
注意：以实际 MySQL 启动脚本路径为准
/etc/init.d/mysqld restart
若报错，注意观察my.cnf配置文件中的内容
3、登陆数据库
/usr/bin/mysql 输入如下命令：
注意：以实际 MySQL 执行文件路径为准
mysql> USE mysql;
mysql> UPDATE user SET Password = password ('新密码') WHERE User = 'root' ;
mysql> flush privileges ;
mysql> quit
4、删除或者注释第一步骤中添加的 spik-grant-tables
5、重启 MySQL 服务
/etc/init.d/mysqld restart
6、使用新密码测试
特殊情况：
我这是使用源码安装的mysql,默认配置文件my.cnf(/usr/local/mysql/my.cnf)中的内容都没有配置，都是在启动文件mysqld(/etc/rc.d/init.d/mysqld)中进行配置的
datadir=/data/mysql
basedir=/usr/local/mysql
若按照上述方法进操作，在my.cnf中添加"spik-grant-tables",则重启mysql时报错
正确的解决方法：
根据启动文件mysqld中的datadir和basedir参数相应的启用my.cnf中的选项，然后再添加"spik-grant-tables",mysql重启就不会报错，也能正常按照下面的步骤进行
未修改前的my.cnf
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
[mysqld]
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
# spik-grant-tables
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
# These are commonly set, remove the # and set as required.
# basedir = .....
# datadir = .....
# port = .....
# server_id = .....
# socket = .....
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
修改后的my.cnf
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
[mysqld]
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
# spik-grant-tables
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
# These are commonly set, remove the # and set as required.
basedir = /usr/local/mysql
datadir = /data/mysql
port = 3306
# server_id = .....
# socket = .....
skip-grant-tables
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
然后再重启mysql,进行下面的步骤，重置密码后，再把my.cnf中的修改的那四项全部注释掉，再次重启mysql即可。