OS X Reversion: Downgrading from Yosemite to Snow Leopard

One of the more interesting requests we get from OWC customers is how to revert from OS X 10.10 Yosemite to an earlier version of the system. The reasons for doing this will vary but the two most common are application incompatibilities and/or a dislike for the changes made to the user interface.

How easy or difficult the reversion is depends heavily on whether you have a full Time Machine backup of the original system installation. As an example, if you are reverting from 10.10 to 10.9 (the next most popular version of OS X) and you have a Time Machine backup, the process is relatively simple. The steps can be found here: https://support.apple.com/kb/PH18846

Reverting to an earlier version like 10.7 or 10.6 can be more complicated, especially without a Time Machine backup. This article provides a detailed look at a recent attempt to revert from 10.10.3 to 10.6.8, without the benefit of a Snow Leopard Time Machine backup. The results were mixed, but mostly positive.

Important Considerations

• This process works only if the version of OS X you are reverting to is supported by your Mac hardware. Please check your Mac documentation to verify compatibility.

• This process is experimental and provided as a courtesy – OWC does not provide technical support for OS X or its apps. If you are having trouble with OS X and you need support, please contact Apple before attempting this process.

• Installing any operating system carries the risk of data loss. Always keep a fully functional, independent backup of your data. (Note: OWC is not responsible for data loss.)

• The process involves the migration of media from the Photos app, iPhoto, and iTunes. Media and libraries used by other apps (e.g. iMovie or Garage Band) have not been verified to work with this process.

• iCloud accounts are not supported in 10.6 but can be accessed from www.icloud.com.

• To avoid any naming confusion: 10.10 = Yosemite; 10.9 = Mavericks; 10.8 = Mountain Lion; 10.7 = Lion; 10.6 = Snow Leopard. We do not recommend using a system earlier than 10.6.8 due to stability and software compatibility issues.

Preparing Photos and Music

The first challenge was to make sure we could transfer media from Photos or iPhoto, as well as iTunes, into the legacy system. Some key points:

• The Photos app does not work in OS versions prior to 10.10. For iPhoto, going back to 10.6.8 means iPhoto 9.5 (2013) or iPhoto 9.6 (2014) cannot be used either. Instead we used iPhoto 9.2 (an updated version from the 2011 iLife suite).
• iTunes 12 works with 10.7.5 or later. For 10.6.8, iTunes 11 is the most recent version.

1.) Using the Finder, create and name a new folder on your Desktop, into which all of the iPhoto Events or Photos Moments can be saved. By exporting all Events or Moments (rather than other collection types like Albums) you give yourself the best chance to ensure no photos will be left behind.

2.) Photos: To export all images in their original state, choose Edit > Select All within the Photos view, then choose File > Export > Export Unmodified Original. Note: this option does not export metadata. To maintain our original file names and Moment names, we also chose “File Name” from the File Name menu, and “Moment Name” from the Subfolder Format menu. Click Export. When Photos asks for a location to generate the subfolders, choose the folder you created in Step 1.

For more information about exporting from Photos, visit:

• https://help.apple.com/photos/mac/1.0/?lang=en#/

iPhoto: Starting from the Events view, choose Edit > Select All, then File > Export. To export unmodified originals choose Original from the Kind menu, otherwise choose Current to export the photos as-is. Note: neither option exports metadata. We also chose Use File Name from the File Name menu, and Event Name from the Subfolder Format menu. Click Export. When iPhoto asks for a location to generate the subfolders, choose the folder you created in Step 1.

For more export options in iPhoto 9.5 or 9.6, visit:

• https://help.apple.com/iphoto/mac/9.5/?lang=en#/
• https://help.apple.com/iphoto/mac/9.6/?lang=en#/

3.) Exporting data from iTunes is a bit easier. Copy the iTunes folder (User > Music > “iTunes”) to the Desktop. This will move the actual audio and media files.

4.) From iTunes, choose File > Library > Export Playlist. This needs to be done for each playlist you want to export. For every playlist exported, this step will generate text files that describe the content of the playlists. No music or media is exported.

For more information on iTunes 12 export options, visit:

• https://help.apple.com/itunes/mac/12/?lang=en#/

Email Accounts
Before installing any new system, it is important to make note of email login information and server settings that are required to send and receive email. If an email account uses the IMAP (Internet Message Access Protocol), no additional steps should be required beyond those just mentioned.

5.) If your email accounts use POP, export those mailboxes to your Desktop.

If you need assistance determining what kind of email account you have or with exporting mailboxes from a specific client like Apple Mail, Microsoft Outlook, or Mozilla Thunderbird, please contact the developer or check their support pages.

Apps and Other Data
6.) Perform a final Time Machine backup. As long as Time Machine is not configured to omit folders (System Preferences > Time Machine > Options), everything installed with 10.10 including the media and email data prepared in Steps 1-5 should be backed up during this process. 

7.) Shut down and boot into the 10.6 installation disc. Note: as of this writing, it was still possible to purchase legacy installers from Apple, for the following operating systems:

• Snow Leopard (10.6): http://store.apple.com/us/product/MC573Z/A/mac-os-x-106-snow-leopard
• Lion (10.7): http://store.apple.com/us/product/D6106Z/A/os-x-lion
• Mountain Lion (10.8): http://store.apple.com/us/product/D6377Z/A/os-x-mountain-lion

8.) Choose Utilities > Disk Utility from the main menu. Find the current system volume in the drive list and highlight it (see below). By default, Mac system volumes are named “Macintosh HD”, but your disk may use a different name if you customized it during a prior formatting session.

9.) Click the Erase tab to access the drive format settings. Make sure the format is set to Mac OS Extended (Journaled), give the volume a new name, and click the Erase button to reformat the drive prior to installing Snow Leopard.

10.) Quit Disk Utility and proceed with the OS installation (follow the prompts on the “Install Mac OS X” screen). The install process may take a while to complete.

11.) When the installation is finished, restart the computer.

12.) After the computer restarts and displays the Welcome animation, follow the prompts in the Setup Assistant. On the “Do You Already Own a Mac” screen, choose to transfer data “From a Time Machine backup”. Click Continue.

13.) From the “Select a Backup Volume” screen, choose the Time Machine volume used in Step 6. Click Continue.

14.) From the “Transfer Your Information” screen do not change the default settings. Click Transfer. This will bring all of the apps backed up from 10.10, into the 10.6 environment. Note: some of them will not be compatible with the earlier OS.

15.) At the end of the transfer process the Setup Assistant requires a user login. At this point do not login. Instead shut down the computer.

16.) Boot back into the 10.6 Installer. At the main screen choose Utilities > Password Reset Utility. Select the system volume, then the user account, and enter a new password. Click Save, then quit the app.

17.) Restart and then login with the original username and new password.

18.) Run Software Update, restarting as directed, until no more updates are available.

Incompatible Apps
The following default 10.10 apps will not work in 10.6, so they need to be removed. This is NOT an exhaustive list. There are likely to be third party apps from the Yosemite installation, which are also not compatible with Snow Leopard – they also need to be removed. If you would like to verify if your third party apps are compatible with both Yosemite and Snow Leopard, please check with the developer.

19.) Move the following apps to the trash (and remove their respective icons from the Dock, if present):

• Calendar (not iCal)
• Contacts (not Address Book)
• Face Time
• Game Center
• Pages
• iBooks
• iMovie
• iPhoto
• Keynote
• Launchpad
• Reminders
• Maps
• Messages (not iChat)
• Mission Control
• Notes
• Numbers

20.) Restart the computer.

21.) Install iLife ’11 if you have the installer disc. Run Software Update until no further updates are available.

22.) Delete the iPhoto Library from the Photos folder, then launch iPhoto 9.2.3 for the first time to create a new library with default settings.

23.) Open the folder created in Step 1, drag the Event or Moment folders into the iPhoto sidebar or Photos sidebar, respectively. This will import all the photos (and Event groupings) into the new iPhoto Library.

24.) Delete the iTunes folder (User > Music > “iTunes”), then launch iTunes and drag the iTunes folder from the Desktop into the iTunes sidebar. This will cause iTunes to import all the music into its new Library file.

25.) Reauthorize iTunes, then import the Playlists from the Desktop.

26.) Open your preferred email client (you will have to download and install it first if you’re not using Apple Mail) and set up the preferences for your email account.

27.) Import POP mailboxes if applicable.

28.) Open the Disk Utility app, highlight the system volume again and choose “Repair Permissions”. The process may take a few minutes.

29.) Restart – 10.6.8 is now ready to use.

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• OWC Ben M. Contributed to this article.