Drop database return “Error dropping database errno: 66” in MySQL

Question

Consider:

DROP DATABASE db_name;
ERROR 1010 (HY000): Error dropping database (can\'t rmdir \'./db_name\', errno: 66)

The problem is that I

Answer 1

FYI for mac users with normal mysql server:

/usr/local/mysql/bin/mysql -u root -pPASSWORD  -e "select @@datadir"