I would like to upgrade to OS X Mavericks. Also, I think it would be a good chance to clean up my system.

My question is: If do a clean install of OS X Mavericks and then restore my machine from a Time Machine backup, then…

  1. would this still be "clean"? …or would this just be the same as upgrading my system the regular way?
  2. will I lose any data/settings/apps?

Thank you guys for your help!


If you reinstall 10.9, don’t choose "Restore from Time Machine Backup". Make a simple install after you reformatted your drive with Disk Utility.

After the install, the setup process will start and you can choose if you want to restore from Time Machine. I would recommend you to deselect the System to restore, just your home directory and your applications. So you will just restore your data (docs, music, pics), your applications settings (~/Library) and the application bundles from /Application.

This the closest you can get to a "clean" install, without manually migrating your data and setup again every single app.

  • Thanks for good advices. I can not find where to deselect the system to restore with Migration Assistant. Might you edit this to have more detailed instructions? – user67580 Jan 15 '14 at 17:15
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    None of this information is relevant or accurate. I think you're confusing Time Machine with Migration Assistant. Simply reinstalling OS X through the recovery HD is as good as a fresh install, and since it will keep Applications (and their respective install files), and any user files intact, it is the safest and easiest solution. – user10355 Jan 15 '14 at 20:09
  • See How to migrate data from another Mac using Mavericks: "You can customize the type of information that you want to transfer …". @cksum Migration Assistant can copy (migrate) files from a Time Machine backup. – sam Nov 8 '14 at 20:26
  • @sam what does "setup process" meant? I found this article how clean install works. At which point setup process comes? osxdaily.com/2015/10/01/clean-install-os-x-el-capitan-mac Migration Assistant should run after the whole clean install completed? – János Nov 6 '15 at 23:36

Absolutely. A clean install is one where the core OS comes from a valid installer. Past that, you can test the system for whatever level of "fitness" you require and only move users, user data and third party apps from a backup in a controlled manner if desired.

I like to look at the loss of data in the opposite direction. When that installation goes badly, the loss has typically already happened. If you don't have a backup and restore system where by you can get back to the pre-upgrade status, you might not want to change anything on the system as you can't really recover from a random failure at that point either - let alone have a good option if the software you have installed isn't compatible with the new OS.

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