Can someone explain to me, or point me to an explanation, how to back up my current OS version (10.6.8) before installing 10.10.2 just in case I later have to revert back to 10.6? Is there anything special that needs to be done? I have the 10.6 install disk, but I'm worried about whether it would let me re-install 10.6 over a later OS version.
(FYI, this is my iPhone iOS paranoia showing through, since Apple seems determined to prevent OS downgrades on those devices. I figure it's only a matter of time before they do the same with Macs.)
