Could You help me

I have installed   the following:


Maquina 1 Postgres 9.1 on Fedora 16 this is the Master

Maquina 2 Postgres 9.1 on Fedora 16 this is the slave


they work succesfull an the replication  too, but when The Master crashes:

1.- How to promote to slave becomes a new Master and

2.- When Old Master restarts:

How to become  old master to slave

How To configure failover in general


thanks