Moving drives around...

[therealseebs]

Long story short: I have a slightly older machine with a largeish (as SSDs go) SSD with all sorts of stuff on it, and 10.7. I have a slightly newer machine with no SSD and 10.8. I am not totally sure whether the new machine would boot and run from the old machine's drive (it's a June 2012 MBP, non-Retina, so I think it came with 10.7 originally, but there might be Deep Magic in the stuff that interacts with EFI...).

I don't actually care that much about 10.8, but if at all possible, I want to avoid either (1) having to wipe out and reload from backups or (2) paying for a 10.8 upgrade I don't actually care about right now. The newer machine was just-purchased refurb, so it qualifies under up-to-date, but I don't know how that is verified or checked, or whether it'd work if it were using a 10.7 hard drive. If not, but it ran okay, I wouldn't actually feel particularly put out.

So mostly I'm seeking advice/ideas. Do the non-Retina 2012 macbooks work with 10.7.5? How does the up-to-date program check eligibility? (Or are all of the June 2012s eligible, in which case that'd at least explain how it knows it is entitled to 10.8.) Is there an apple recovery option I overlooked for "keep this drive's user data, apps, and settings, but upgrade OS X to 10.8 if you need to?"

EDIT: A few notes:
I've never bought 10.8 as an upgrade. So even though the new machine has 10.8, it doesn't appear that I can use it to obtain the 10.8 installer, which I would need to have to run an upgrade of the existing drive. So far as I can tell, anyway, regardless of which drive is in the machine, or how it is connected, the new machine has no options other than "fresh install of 10.8". This wouldn't be an issue, except that in this case I want to use that specific drive, because it's an SSD, and I don't have another SSD large enough to replace it.

 

[therealseebs]

So, before wiping out anything I cared about, I figured I'd test that recovery worked, so I took a spare drive, hooked it up, and had the new machine's recovery try to install to it.

Two and a half hours later, the machine tried to reboot to that drive, and failed. Went back to recovery, popped a terminal, and discovered that... that drive somehow ended up holding 10.7. I think that is what it previously had (it was the drive that came with an older MBP), but it seems strange to me for the installer to run for two and a half hours and somehow not actually change what's on that drive.

Have erased that drive, running the installer again to see whether it perhaps works that way. This doesn't really help much, since to make that work, I'd still have to do complete backups and wipe out my existing install. I've submitted a request for the up-to-date program license, because the description of the machine said it qualified for Mountain Lion under up-to-date, but I don't know whether they'll actually do that. (If they did, I'd have a real OS X installer, and then I could use that to update the copy of OS X on the existing drive, and all would be well.)

 

[therealseebs]

Poking around, I found references to a process by which one could take a disk on which recovery had run the first part of the process (the long download) but not yet done the reboot, and copy the recovery image off it. Did that, successful. Tried to copy it to other media for use. Not successful. Eventually, booted the drive on the new machine (using the old machine in target disk mode) and ran the installer out of the recovery image, got 10.8 installed, swapped drives, all is well.

 

[therealseebs]

Just a followup, since the question may someday affect other people:

Machines which say they qualify for up-to-date may not actually qualify for up-to-date. In some cases, they will instead ship with 10.8 pre-loaded, and NOT qualify for up-to-date (which would add 10.8 to your app store account). But so far as I can tell, interrupting the recovery process at the reboot after it's downloaded gets you the installer, which can then be run to upgrade an existing install instead of wiping it. I think.

For future reference, had I actually had pending work to do in reasonable amounts, and spent the same amount of time I spent on this working, I could have bought a new SSD and just about come out ahead on the deal...