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macrumors 6502
Original poster
Sep 9, 2008
I have a late 2012 27" iMac (13,2) and tonight I tried to update it to Mojave (currently HS 10.13.6). It downloaded just fine, but as soon as I agree to the terms and conditions, it says it cannot verify the drive and that I should start up in recovery mode to run Disk Utility to repair it.

So I did that, and Disk Utility right away says the drive is corrupt and cannot be repaired....The machine seems to run just problem that I can tell at all with it, so this is an unfortunate surprise.

I guess I need to know what my options are. I hate to give up on this iMac because it is a BTO machine that I upgraded at the time of purchase with 3.4Ghz quad-core i7, upgraded graphics, and I've also already upgraded the RAM to 32 GB. Internal drive is a stock 1 TB Fusion drive.

Is it true that I would have to buy a new display/glass in addition to buying a new SSD drive? Just in order to get inside the machine in the first place? Not to mention paying somebody qualified to do it? This is sounding really expensive or maybe I'm uninformed. Thanks for any and all help.
Last edited:


macrumors Penryn
Feb 20, 2009

The LAST THING I would suggest is that you go tearing into the iMac, just so you could "upgrade" to Mojave. That's ridiculous.

What I WOULD suggest is that you do this:
1. BEFORE you do ANY upgrading, you need a bootable cloned backup of your OS setup AS IT IS NOW. You can create one with either CarbonCopyCloner or SuperDuper. Both are FREE to download and use for 30 days, so creating a cloned backup "costs you nothing" except the time consumed in making one.
2. Of course, you'll need an external drive with which to do this. I suggest that you format it to "Mac OS extended with journaling enabled" (HFS+) -- NOT to APFS.
3. The reason for making the cloned backup is, if anything goes wrong with the "new install", it's easy to "get back, get back, get back to where you once belonged". No cloned backup, and it's going to be the struggle of your "computing life" to do so.
4. You should also consider using a USB flashdrive to make a bootable USB version of the OS installer. Things can go better this way.

5. You'll want to boot from the USB installer, then...
6. ERASE the internal drive (again, to Mac OS extended with journaling enabled), then...
7. Try the install that way

If the install is good, you should boot to the setup screen. Then...
a. begin setup
b. at the appropriate moment, setup assistant will ask if you wish to migrate from another computer or drive. YES, you want to do this, so....
c. connect the cloned backup and let setup assistant take a few moments to "digest things", then...
d. select from the options that setup assistant provides (you'll want to select everything), then...
e. let setup assistant "do its thing".

When done, you should be presented with a login screen just as it was on High Sierra.


macrumors 6502
Original poster
Sep 9, 2008
Thanks for the help. I am looking into getting a TB external SSD, but they are rather expensive. At least at OWC.

Honestly, I have no real need to update to Mojave anyway, but was looking forward to 'under the hood' improvements. I definitely want to keep this iMac around for a few more years, so replacing the Fusion drive with an SSD is OK with me.

I do have a Time Machine, although I'm a little embarrassed to say I've never actually used it other than for it's Airport Extreme functionality. I do like the idea of a cloned backup though, and will look into that.

Also, I had no idea the CPU on this iMac is actually upgradeable? Wow.
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