Downgrading OS X without losing anything
Some have asked me how to downgrade OS X without losing any files, applications and data. I decided to write a brief tutorial of downgrading from OS X 10.10 to 10.9. The same process applies for downgrading from 10.11 to 10.10.
1) You now have OS X 10.10 with personal documents and apps. You want to go back to 10.9 but keep everything.
2) You need a 10.9 installation USB drive. You can make it by following this tutorial. https://support.apple.com/en-us/HT201372
3) If you use iWork’14 (Pages 5.5.x, Numbers 3.5.x, Keynote 6.5.x) outside of iCloud Drive, open those documents. Go to File — Advanced — Change File Type, and change them from “Single File” to “Package” one by one. If you use iWork’15 (Pages 5.6.x, Numbers 3.6.x, Keynote 6.6.x), export your documents to Word, Excel and PowerPoint one by one.
4) If you have Final Cut Pro libraries that are in 10.2.x format, open them, choose File — Export XML— and save them as XML (version 1.4). If you use iMovie, finish all your projects and export those into media files.
Preservation (of Data)
6) Power off your Mac. Hold option key. Choose to boot from the newly-created USB drive.
7) When presented with multiple Options, choose Utilities - Terminal.
8) Navigate to your Mac’s local hard drive partition (which contains 10.10) by typing “cd ..” multiple times, then type in “cd Volumes”. Then type in “ls”. Type in “cd + ‘name of your drive’(does not include plus sign or quotation mark)”
9) Type in the following commands. Once you finish typing one line, press enter and wait for the command to complete. Some processes may take a few mintues.
mv Applications App1 mv Library Lib1 mv System Sys1 mv Users User1 sudo rm -rf .DocumentRevisions-V100 sudo rm -rf .Spotlight-V100 sudo rm -rf .fseventsd sudo rm -rf .Trashes sudo rm -rf .vol sudo rm -rf bin sudo rm -rf cores sudo rm -rf etc sudo rm -rf home sudo rm -rf mach_kernel sudo rm -rf net sudo rm -rf Network sudo rm -rf private sudo rm -rf sbin sudo rm -rf tmp sudo rm -rf usr sudo rm -rf var sudo rm -rf Volumes
Downgrade (of OS X)
10) Then close Terminal and choose to “Install/Reinstall OS X”.
11) The installation will proceed as normal. Set up account like how you set up a new Mac.
Restoration (of Data)
12) After you log in, everything is fresh. Don’t worry. Go to Finder. Choose “Go” — “Go to folder”. Type in “/” and press enter.
13) You’ll see a few extra folders, named App1, Lib1, Sys1 and User1. Those are where our preserved user data are located in.
14) Go to App1. Move every non-system app (apps you’ve installed yourself) to the actual local Applications folder. Some app may no longer be compatible with that previous version of OS X. Trash them [except Xcode if you use it] and re-download legacy compatible version, either through Mac App Store, or software vendor. When done, trash “App1” folder.
15) Go to Lib1 and go to “Application Support”. You only need to move supporting files from here to /Library/Application Support if you have installed non-sandboxed OS X apps (usually from clunky pkg packages instead of drag-and-drop dmg images or Mac App Store apps, such as legacy versions of Office for Mac, professional software like ProTools or Adobe apps).
16) Now it’s the Users folder. If you face denied permission, right click on your previous user folder, choose “Get Info”. Then click the lock icon, enter your password to unlock changes. Delete everything but “everyone”, and change Privilege to “Read & Write”. If you don’t face denied permission, proceed.
17) Go to your old user folder, again, move/drag every document (or data) into the actual new user folder.
18) Photos app’s library will not be compatible with iPhoto. If you put everything under Photos, right click the Library, choose to “Show Package Contents”, and drag out JPEG files from “Masters” folder. Then reimport them to a clean iPhoto library. You will lose all non-destructive edits, albums, slideshows, face data and other organizations. They need to be regenerated or recreated.
19) iTunes library may not open in a previous version of iTunes that come bundled with that version of OS X. Download the latest version of iTunes either in Mac App Store (10.8 or above), through Software Update (before 10.8) or from iTunes.com. If you’ve used TinyUmbrella to backup firmware APTickets before, be sure to get all data from a hidden folder at “/Users/old user name/.shsh”.
20) [Optional] Launch Final Cut Pro X 10.1.4. Import those previously exported XML files so that you’ll keep access to all your projects.
env DYLD_INSERT_LIBRARIES=$ABSOLUTE_PATH_TO_FRAMEWORK/xpf-bootstrap.framework/xpf-bootstrap /Applications/Xcode.app/Contents/MacOS/Xcode
22) Now you need to choose “Go” — “Go to folder” again. This time, type in “/Users/old user name/Library” and press enter. You’ll see app preferences, support files and perhaps documents. Knowing what’s necessary and what’s not requires some understanding about how OS X works. Here are some of the folders that contain useful data:
Application Support — Again, you only need to move supporting files from here to ~/Library/Application Support if you have installed non-sandboxed OS X apps. Notice this time, they should be moved to “~/Library/Application Support”, rather than “/Library/Application Support” as they should be in user folder. Common app that need doing so is Adobe. Do NOT move everything in this folder to your previous system. Just do so for pro apps/clunky old pkg apps.
Containers — Sandboxed apps save data, caches and settings here. For example, epubs in iBooks is saved under com.apple.iBooksX. Data are usually in “Documents” folder, and preferences are often in “Library” folder. Again, they may not be directly compatible with older counterparts, especially if they’re system build-in apps. You may need something like “sqlitebrowser” to open databases/configuration profiles (in this case, bookmarks and annotations will only be accessible through reading sqlite databases, but books themselves can be repackaged as epub and reimported).
Fonts — Fonts you’ve installed. You can just move them to “~/Library/Fonts” without any problems.
Keychains — Saved passwords. Don’t directly move them. Instead, copy them to a safe location. Then import them through Keychain Access app.
Mobile Documents — Everything you saved in iCloud Drive/iCloud Documents & Data. iCloud Drive will not be compatible with OS X 10.9 and below, and once your account is updated for iCloud Drive, it can not be reverted. However, you can copy these documents to a safe location, such as the user Documents folder, and create a new iCloud account, enable Documents and Data, copy them back in and re-sync them. Don’t copy folder structure. Just copy your files into the correct container OS X newly generated.
Safari — Bookmarks and History. You can only move “Bookmarks.plist”, “History.plist” and “TopSites.plist” plist files to “~/Library/Safari” without any problems. Do not move any other files.
Widgets — Move widgets out to a safe location. Double click to reinstall.
I know you may be tempted to move stuff I haven’t mentioned here, but trust me, unless you’re 100% certain, don’t move them to your current Users folder. Most of the other stuff can and will be regenerated, such as iLife stuff, default preferences or caches.
Hint: “sqlitebrowser” can open databases/configuration profiles that are no longer compatible with previous versions of corresponding app counterparts.
23) Now it’s up to you if you want to leave the Users1 backup folder there. If you think you’ve got everything, trash it.
24) Enjoy! You’ve downgraded OS X without losing any data or apps!
The same tutorial is also posted on MacRumors Forum. I am the author of this tutorial.