If you followed previous post about init script (here and here) for Percona XtraDB Cluster, I proposed a new solution to standardize the bootstrap of the cluster in debian/ubuntu and redhat/centos instead of using 2 different ways.
You can read about this on launchpad bug #1152764.
So now to start the first node of a cluster when no other node is already running, you just need to use bootstrap command with the init script like bellow:
# /etc/init.d/mysql bootstrap Starting MySQL (Percona XtraDB Cluster)..... SUCCESS!
I attached the patches here too.