Once Corosync is running, you are able to start the Pacemaker cluster resource manager on all cluster nodes:

service pacemaker start

Once cluster startup is completed, you should see output similar to the following when invoking the crm_mon utility:

============
Last updated: Mon Dec  3 15:37:59 2012
Last change: Mon Dec  3 15:37:58 2012 via crmd on alice
Stack: openais
Current DC: alice - partition with quorum
Version: 1.1.7-ee0730e13d124c3d58f00016c3376a1de5323cff
3 Nodes configured, 3 expected votes
0 Resources configured.
============

Online: [ bob alice charlie ]

This article originally appeared on the hastexo.com website (now defunct).