Update from OS X 10.8 to 10.10, then roll back?

[ArtOfWarfare]

I need to develop an iOS 8 app while I'm on a trip. This necessitates a laptop running 10.10 (Yosemite). My 2008 MBA can't update to that. So a relative is loaning me their 2012 MBP.

Here's the problem: it's running OS X 10.8 (Mountain Lion). I know how to update it to 10.10 just fine, but the relative is highly resistant to change - I need to update it for the two weeks that I'm borrowing it, then restore it to its current state, 10.8 and all, without any hint of the fact that it had been running 10.10 for the two weeks.

Also, I'm strapped for cash (if I wasn't, I'd just buy myself a new laptop). I can't afford buying any new hardware. The harddrive in the laptop has, according to About This Mac, "486.24 GB free out of 499.25 GB".

Maybe if there's some way to like, install OS X Yosemite on a separate partition, then obliterate that partition and rejoin the space it took up to the existing 10.8 install, that would be perfect.

I'd appreciate any help anyone has. Please include steps for what exactly I need to do (I know I just used the word "partition", but I don't really know how to do that, especially not on OS X. I've done some stuff kind of like it on Red Hat before... does OS X use a logical volume manager?)

 

[ArtOfWarfare]

This looks like it could be super useful:

http://osxdaily.com/2011/03/12/how-to-install-dual-boot-mac-os-x-10-7-lion-and-10-6-snow-leopard/

Just one thing that concerns me... they mentioned having an OS X installer application. Does Mavericks and Yosemite have a similar application that they utilize for installation? It seemed to me that the process was you clicked "Update" in the Mac App Store, then your computer rebooted into some kind of "set me up for Yosemite"-mode or something like that... maybe I'm not remembering properly...

 

[hallux]

When you select to update from the Mac App Store the computer downloads an installer to the Applications folder and auto-launch the update, CMD-Q on the update window. You can then create an installer drive (16 GB or larger USB drive needed according to the link). Once you've done that, I THINK you can just follow the instructions in the article you linked.

Please don't take this as gospel just yet. To be ABSOLUTELY safe, you could always make a SuperDuper or Carbon Copy Cloner copy of their system to return it to pre-loan condition, as long as you have a drive of equal or larger size that you don't mind formatting. It also goes without saying, be ABSOLUTELY sure they have a current full backup of their own before you start playing with it.

 

[chown33]

There's only about 13GB in use on the MBP's disk. Create a partition on any disk you already have that's at least that big (maybe 2GB bigger). Then Carbon Copy Clone the disk to that partition. Confirm that its bootable by booting from it on the source machine.

You now have a restorable duplicate of the original disk.

You can now proceed to erase, partition, install whatever you want on the 2012 MBP.

To restore, simply erase the MBP disk and Carbon Copy Clone the saved partition back to it.

A 16GB SD card costs well under $20, and would be more than adequate for copying the original system to. You can even boot from it to test it. A USB 3 flash drive will also work. I've booted from both of these before, and while a bit slow, they do work.


Oh, and OS X partitions are created and managed in Disk Utility.app. If you've never done OS X partitions before, you should practice on a disk (or SD card or USB flash drive) whose contents you don't care about. This is also why you should confirm that the cloned copy is actually bootable by booting from it. This is all to avoid digging yourself a hole you can't get out of.