xtrabackup: Error: Please set parameter 'datadir'

Hi,

I am using percona-xtrabackup-2.0.2’s innobackupex to do a full backup of my existing mysql database.

Its giving me the error " xtrabackup: Error: Please set parameter ‘datadir’ ".

Why do we need to mention datadir? Does not it pickit up from my.cnf?

Please help its very urgent

I am getting the above error when i am running from the script. But when i am running innobackupex manually i am receiving the error

innobackupex: Error: Failed to create backup directory /mysql_bkup: File exists at /u01/home/xtrabackup/product/percona-xtrabackup-2.0.2/bin/in nobackupex line 374.

I am using the below command to execute a full backup manually

innobackupex --port=<port_no> --socket=/tmp/mysql_<port_no>.sock --no-timestamp /mysql_bkup

Please suggest

Some one please suggest