xtrabackup does not have access rights

I’ve just installed percona-xtrabackup, and so for my first test I have Created a Directory (testdata) in my Home directory:
mkdir testdata

changed permissions on it
sudo chmod 777 testdata

and ran innobackupex
innobackupex --user=root --password=xxxx /home/user/testdata/

But I then get:
2015-03-26 16:37:54 7fee54ebd740 InnoDB: Operating system error number 13 in a file operation. InnoDB: The error means mysqld does not have the access rights to InnoDB: the directory.

Is this the datatest directory, or my MySQL ‘/var/lib/mysql’ directory, or somewhere else?

it turns out it’s my fault. I needed to use sudo innobackupex. . .