If  you forget the mysql root's password,you can follow these steps to reset:

1.stop all  mysql processes (use kill or killall)
2.run  /usr/bin/mysqld_safe --skip-grant-tables&(mysql safe mode)
3.now you can login as root use empty password
4.change the password with following commands:
   a.  use mysql
   b.  update user set password=password("new_pass") where user="root";
   c.  flush privileges;
   d.  exit
5.kill all mysql processes
6. restart mysql and login as root use new_pass