How do I downgrade from Mountain Lion to Snow Leopard?

Downgrade Lion/Mountain Lion to Snow Leopard

1. Boot from your Snow Leopard Installer Disc. After the installer

loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the

Utilities menu.

2. After DU loads select your hard drive (this is the entry with the

mfgr.'s ID and size) from the left side list. Note the SMART status

of the drive in DU's status area. If it does not say "Verified" then

the drive is failing or has failed and will need replacing. SMART

info will not be reported on external drives. Otherwise, click on

the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions

from the drop down menu to one. Set the format type to Mac OS

Extended (Journaled.) Click on the Options button, set the

partition scheme to GUID then click on the OK button. Click on

the Partition button and wait until the process has completed.

4. Quit DU and return to the installer. Install Snow Leopard.

This will erase the whole drive so be sure to backup your files if you don't have a backup already. If you have performed a TM backup using Lion be aware that you cannot restore from that backup in Snow Leopard (see below.) I suggest you make a separate backup using Carbon Copy Cloner.

If you have Snow Leopard Time Machine backups, do a full system restore per #14 in Time Machine - Frequently Asked Questions. If you have subsequent backups from Lion, you can restore newer items selectively, via the "Star Wars" display, per #15 there, but be careful; some Snow Leopard apps may not work with the Lion files.

Kappy almost got it right.

What he didn't mention is that you need to get your files off and out of Mountain Lion program versions into neutral states as possible so they can be imported into 10.6 compatible versions of programs. Newer propreitary versions of programs alter their files and thus can't always be read by older verisons of software comaptible with 10.6

How to revert your Mac to Snow Leopard

iTunes folder should work in 10.6 as when you update to 10.6.8, it's iTunes 11 just like on 10.8, if not then you can extract the content manually.

iPhoto Library, you really should export all those pictures (right click on iPhoto Library and "show package contents" for the Originals folder), also in any other program that newer versions of software may have altered their support files containing your originals. Like Aperture or Lightroom etc. Their packages also can be right clicked on and opened.

You need files into neutral formats like jpg, gif, txt, mp3 and so forth so they can be imported easily into 10.6 compatible versions of programs.

How to revert your Mac to Snow Leopard

Save everything you can (like exporting bookmarks, passwords, email addresses etc) to a external storage drive, DO NOT use TimeMachine as it doesn't work in reverse. You CAN make a Carbon Copy Clone of the 10.8 boot drive, then access it from 10.6 later, but I wouldn't take a chance on that alone.

Most commonly used backup methods

Once you have you files off, and the drives disconnected. Like in #1 Kappy said, but he didn't mention how to boot off the 10.6 disk, you do this by holding the c or option key down on a wired or built in keyboard.

When your Erasing the ENTIRE INTERNAL DRIVE in Disk Utility (this is a must!), you should take this opportunity to Security Erase > Zero All Data, this will take some time and really check the drive out for errors and map them off, it's worth it for a much more reliable hard drive that has less software issues later on, it acts like a perfect running machine.

If you don't erase the entire drive by selecting the drive makers name and disk size at the top, and only erase the Macintosh HD partition, 10.6 will install, however if you later have a problem you can't repair the drive using the 10.6 install disk because the hidden altered GUID and Recovery HD partitions are on there from 10.8 and 10.6 Disk Utility doesn't know what it is so it can't fix it.

At this point this method will work

How to erase and install Snow Leopard 10.6

Having been used by countless users successfully, how can you say it's "almost right?"

Unhappy Kappy? 😁

I've written another tip that also inlcudes performance tweaks

Snow Leopard Speed Freaks

Hitachi makes the best drives, even though they are owned by WD now, it's still their factory.

All drives work well, it's the ones with "sleep", "energy saver", "eco drives" "green" or hybrids, or some sort of built in RAID that causes issues.

It's not going to be used 24/7, you don't want it turning itself off neither. No brains, just a standard powered drive that works well.

Dont go too big, as 10.6 Disk Utility chokes on these massive 3TB drives. Stick to what is the same size as your boot drive and your good.

Yes. Make an appointment.