Reformat and re-install Mountain Lion via the Apple Store

[HippoMan]

I'm currently running Mountain Lion.

I want to completely reformat my disk and re-install a fresh, "virgin" copy of Mountain Lion on my machine.

I originally did the Mountain Lion installation via a direct download from the Apple Store (after paying $19.99), and I don't have a DVD with the OS. Is there any way to do one of the following things?

1. Boot into recovery and then do a reformat/reinstall of Mountain Lion by somehow directing recovery to get the OS directly from the Apple Store?

2. Somehow download a DVD-burnable image of Mountain Lion from the Apple Store so I can use it via recovery to reinstall my OS from a DVD after a reformat?

3. Some other method ... ???

If at all possible, I don't want to order a DVD from Apple, and I especially don't want to spend any more money to accomplish this, given that I already spent the $19.99 for my original Mountain Lion installation over the internet.

Thanks in advance.

PS: My Mac is more than three years old, and it's not one of the "new Mac models introduced after public availability of OS X Lion or OS X Mountain Lion". Therefore, it doesn't have the "OS Internet Recovery" feature described here: https://support.apple.com/kb/HT4718

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[benwiggy]

You should be able to erase and re-install the OS from the Recovery Partition. That's what it's for. Internet Recovery, which you don't have, is a Firmware version of the Recovery Partition, in case the Recovery Partition itself goes down.
But otherwise, the Recovery Partition will install the OS, connecting to Apple to get the latest version.

Alternatively, there are many Mac webpages which describe how to get the disk image out of the Installer app that downloads from the Store, and then restore that onto a USB drive. (It's just slightly too big for a DVD, so you need an 8 Gb flash drive.) Basically, just open up the app package and it's called "InstallESD.dmg".

[HippoMan]

Thank you very much, benwiggy. I'll look into how to get the disk image out of the installer.

As for the Recovery Partition, I'm unclear as to how to use it in the way you describe. Does this involve booting into recovery mode, or is this something I can do via Disk Utility?

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[DeltaMac]

The Recovery system is on a hidden partition.
Restart, holding Command-R. You will boot to your Recovery system.
You CAN then run Disk Utility, erase your hard drive, and proceed on with a Mountain Lion Install.
Best method for this is to (before you erase the hard drive) to go to the App Store, download the Mountain Lion install again (you already bought it, so you won't be charged again.)
Before you let it actually install (the complete installer is deleted once the install finishes, so you want to wait till later to actually run the install), you can google for several different methods to make an external installer, I recommend the 8GB flash drive. It's really easy with this utility, too. http://www.macupdate.com/app/mac/39701/lion-diskmaker
Although that utility can easily make a bootable DVD, I don't recommend that particular use. Lion and Mountain Lion seem to not be optimized to install from a DVD - plus a new 8GB USB flash drive is less than $10 (maybe on sale for a lot less!)
And - the result is something that you can keep, and then update to latest version as Apple releases updates to Mountain Lion (Apple recently updates the full install very quickly, so you can download the very latest version at any time, and then redo that flash drive with the absolute newest installer.
After that is complete, you can boot to your own installer, and then the erase and install will be very straightforward for you - plus, you don't need to wait for all the files in the installer to download over the internet. Your Recovery partition does not have all the installer files - it's only a 650MB partition.

[HippoMan]

Thanks, DeltaMac.

I think I understand. Let me state this back to you in my own words, to make sure I don't have any confusion about it ...

1. Download the installer from the App Store. The resulting bundle will be this: /Applications/OS X Mountain Lion.app

2. Using Lion-Diskmaker, extract the installer from this onto a USB drive (I have one already which is either 8GB or 16GB).

3. Boot into recovery by holding down Command-R during the startup sequence.

4. Go into Disk Utility, and reformat my hard drive.

5. Then, reinstall my OS via the external installer on my USB drive.

Is this correct?

I'm still not sure how to perform step 5, but I'm sure I can find easy instructions for this on line.

Thanks again.

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[DeltaMac]

If you have that installer on a USB drive, then there's no reason to boot to the Recovery partition (you can't run your external installer from there, and you would have to restart to that installer anyway)
Just insert your Mountain Lion flash drive, then restart your Mac, holding the Option key. Choose your USB installer from that Option-boot screen, and press enter. And, you then will boot to the installer. It will look identical to the Recovery partition that you already know about. You can erase the hard drive through Disk Utility, if you want to do that, and then continue with the OS X install. The difference will be - the installer starts copying files across immediately, without needing to download all the installer at that point. So, the total install time will be less than running from the recovery partition

[HippoMan]

OK. I see. Thank you!

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[HippoMan]

Well, my USB drive is broken and it's too late for me to go out and buy a new one tonight, so I now want to try this a different way.

I assume the following should work:

1. Boot into Recovery.

2. Select "Disk Utility" from the OS X Utilities menu and reformat my hard drive by selecting the "Erase" option for that volume and answering all the appropriate questions.

3. Select "Reinstall OS X" from the OS X Utilities menu and connect via WiFi.

4. Install the MacOSX via the internet.

I just want to confirm that these are indeed the correct steps.

Thank you very much.

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[anthlover]

Should work, not the Internet part unless your firmware supports it which you seem to think it did not. Recovery partition should work.

*** Important questions:

*** Are you backed up. How are you backed up?

Why do you want to reformat and start over. No harm if your backed up just curious. I would highly recommend you make sure your backed up and getting a 8GB or larger USB stick is cheap and a good idea. I assume you already tried reformatting the USB stick you have (MAC/HFS format). You can use Carbon copy cloner to make the stick bootable, though that is not strictly necessary.

[benwiggy]

Yes, it should work. I have a 2006 iMac and a 2009 MacBook, both of which automatically connected to my wireless router when booting from the Recovery partition.
(I was kind of freaked out by this, because I was wondering how the OS on the RP got the password for the router! I'm fairly sure I didn't supply it. But I could be wrong.)

As I've said, the whole point of the Recovery Partition is that it is in essence a replacement for the installer DVD. You are supposed to be able to reinstall the OS from it.
But as long as you've got a backup, you'll be fine.

[HippoMan]

Thank you very much. Yes, it all worked fine.

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