I have a snapshot of the root filesystem that I want to boot with - bring the machine into a state it was a few days ago, run some tests and then go back to where I am right now.
I tried editing fstab and just setting the snapshot to boot as root, but it seems that nothing happened - the snapshot was mounted, but the state of the filesystem didn't change, I'm still at the current state.
Edit: There are no other partitions except root. The snapshot is RHEL 6.2, the current state is RHEL 6.3 (so there is a new kernel). I edited intrd by following this blog article and it seems now that the lvms don't get activated at boot. Dracut writes that all of them are inactive by inherit and freezes.