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If the system doesn't boot up (it was due to this issue), is it better to reinstall OS X Lion, or restore from a Time Machine backup?

I do see a Time Machine backup from 3 AM last night, so if that is used to restore the machine, will it read all 600 GB from the external backup drive and copy it to the iMac's hard drive, or will it just do the selective restore, kind of like Windows 7's setting a restore point, and any rollback should be partial - i.e., it only needs to restore a few files to make the system work fine again, but is it the same as on OS X Lion's Time Machine restore?

Is restoring a better approach than reinstalling OS X?

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Also keep in mind that doing a clean install and then backing up to the Time Machine will result in not keeping as clean of a install as you would think. I for instance have problems with the audio kext having throwing errors whenever i install a program that uses it and this problem was carried over after i did a clean install and then restored with Time Machine. –  Chad Marmon Jun 12 '12 at 19:16

2 Answers 2

A Time Machine restore will restore to the last point in time in the backup. A fresh install of Lion will bring your machine to new status.

However, if you do a fresh install and tell it to use the Time Machine backup to restore your data, it will also bring it back to the same point in time.

Some people [citation needed] prefer to use this opportunity to do a fresh install and then selectively drag the data they want from Time Machine back again.

However, keep in mind that if you set up a new backup, it could overwrite the old one.

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They are basically the same in the end - one lets you play with the new OS and the other installs and starts the migration. Yes - if you make a new account, you'll have to delete that and the old account you migrate will no longer be the "first account" created, but for most people, this is a hidden detail that won't change how they work.

If you are looking to isolate why the Mac failed and see if it works again after the re-install, you should take the time to install a clean system and then test. If that works, you will have isolated your backup from the list of potential causes of the issue.

If you go for the restore and it's still broken, you won't know if it's a problem with the hardware or your current image. (and then have to re-do the erase and then test).

There is no clear winner - it's a guess and you might waste time you don't need if a restore fixes everything. That could be a waste if you still need to run a clean install to determine something has failed and then seek a repair.

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