一般还有如下提示：
If you compiled from source, you need to run ‘make install’ to
copy the software into the correct location ready for operation.
If you are using a binary release, you must either be at the top
level of the extracted archive, or pass the –basedir option
pointing to that location.
所以我们按照提示把basedir 也加上：
/usr/local/mysql/bin/mysql_install_db –user=mysql –basedir=/usr/local/mysql –datadir=/xxx/mysqldata