From the research I just did, it seems that I had to upgrade to Yosemity using a different drive!? Where as I added Yosemity into the main drive. Am I right in thinking that I now can only downgrade by reformatting the hard drive (loosing my data and so forth)?
Apparently I'd be able to reinstall Mavericks via the internet holding command-option-r. Does this mean I don't need to have a copy of the Mavericks installer? And since I am re-formating the main drive, would this method still work.
Basically, apart from losing my data, and the hours it will take, is there a chance that I format the main drive and something going wrong and ending up without an operating system?
Best Answer
As of today there is no known way to downgrade from Yosemite to Mavericks without erasing the drive.
Booting to the
internet recovery mode
altcmdR means that you boot to a netboot image containing a basic system downloaded from Apple/Akamai. You don't need the Mavericks installer. If you reinstall a system the system originally shipped with your Mac will be loaded.Boot process (takes 2 minutes connected to a 50 MBps-line):
Boot process finished:
Translation:
Festplattendienstprogramm: Disk Utility
OS X erneut installieren: Reinstall OS X
Starting
Disk Utility
looks like this:Now you just have to repartition your Macintosh HD: 1 Partition & GUID partition table (available via
Options
)If you stuck here unable to partition your drive because it's forbidden or greyed out, your Macintosh HD was probably converted to a CoreStorage Volume Group. Please check and execute the steps 10-12 of my answer to this question. Afterwards you have to start
Disk Utility
again and partition the drive to your needs.BTW: SystemUSB is an attached thumb drive with a bootable system and disk2 (OS X Base System) is the netboot image you downloaded and booted to earlier in step 1.
Quit
Disk Utility
to get to the menu again (picture 2)Reinstall OS X
. Now probablyLion
is downloaded to your newly created hard disk partition and installed there afterwards.If you get a message like 'Could not find installation information for this machine' just restart your Mac to the
internet recovery mode
. (The netboot image seems to be very picky with the WLAN connection and it took me two attempts to get around this step)If you choose the
recovery mode
cmdR the latest system will be installed. You need a workingRecovery HD
-volume though. Such volume won't exist on a brand new hdd.In both cases a stable and fast internet connection will be convenient.
Using the
internet recovery mode
you won't end up with an 'unbootable' system (depending on the reliability of your internet connection) because your (maybe falsely partioned) hdd is never involved in the (net)boot process.In your case (MacBook Pro early 2011) i would download 'Mavericks' with your App Store account, create a 'Mavericks Installer' thumb drive, boot to it and continue with step 2 outlined above. It's just faster and more reliable than first downloading and installing Lion and then Mavericks.