Upgrading OS X 10.6.8 to Mavericks on MB Air As we all know Maverics is not available on AppStore anymore so I downloaded my "purchased" Mavericks from another MB Pro I have. Someone here asked the similiar question and several people advised to make a bootable usb-drive and restore the system from it.
My questions is - can I use the 5,33Gb file I downloaded from "purchased" to simply upgrade without the need to backup my MB Air first? Should I copy the file to a specific folder or may just use Desktop?

Thanks!
I think the best option would be to create a bootable USB drive and install from there. But if you need to do it via a local file, I would copy the Upgrader File to the /Applications folder of the MB Air. 

Yes, you should make a backup. Especially since you are jumping a couple versions of the OS. 

(In truth, I have not had a problem with any of the 30 or 40 upgrades I have done with Mac OS X in the last 4 or 5 years. But I always had a backup, unless I was planning on wiping the system clean. )