My Lion installation ruined. Everything doesn't work. Even my Mac doesn't sleep. I want to reinstall whole OS, but I have no spare backup drive. So I want to reinstall OS without erasing or repartitioning to keep my data on disk.

I know it's not clear enough, but it should be a lot better than my current installation. So I want to try anything if it keep my data without backup.

Is this possible? How can I do this?

Or is there any way to repair current installation?

  • 1
    one solution is to create another partition for installing lion and then using migration assistant to move it from the old partition to the new one – user6124 Jul 26 '11 at 5:26
  • you really want to keep the Recovery partition, it's hidden, but if you partition drives it may not be created, which would be a shame. – chiggsy Jul 26 '11 at 7:31
  • @Pekka 웃 Is this active still? It shows posted 5 years ago but bounty ends in 4 days? – norcal johnny Sep 29 '16 at 2:32
  • @norcal yes, it’s still active. I’m looking for official confirmation that reinstalling Lion through the recovery console will only refresh the system files and not destroy user data. I’m reasonably sure now that this is the case (actually about to try it today) but if you can provide an answer (perhaps an up to date one) that’s great – Pekka Sep 29 '16 at 7:52
  • Ok, thanks for the heads up, I will submit an answer shortly. – norcal johnny Sep 29 '16 at 7:59

Reboot your Mac. When you hear the boot chime, hold the COMMAND + R keys. You will enter the Lion Recovery environment. From there, simply choose to reinstall Lion. It will simply remove the current system and replace it with a fresh copy. None of your data will be deleted or moved. The only thing that will be replaced will be the core system files. There is no longer any need to make backups, migrate your data, or mess with partitioning.

If you'd like to read more about the Lion Recovery function, go here: http://support.apple.com/kb/HT4718

  • This is not what the document tells me - it suggests reinstalling the OS before giving it away. Is this really correct? – Pekka Sep 26 '16 at 15:38
  • This is the correct answer. Erasing data and installing OS X was referred to as a "clean" install of OS X in the pre-Lion era. The Lion installer does not include an option to perform a clean install. To remove existing data, you'd need to use Disk Utility to erase the disk and then run the Lion installer. See here for more confirmation that installing OS X Lion from Recovery does not erase your disk: apple.stackexchange.com/questions/47351/… – Adam Rice Oct 3 '16 at 2:55

I'm in the same boat. Kernel panics malloc errors everywhere PAH!


Download Lion. The install eats the file you need so don't install it right away. Only took me 2x +XCODE to figure that out.

Now, if you installed it you can do the brutal cmd-R on boot to get to the recovery partition. That's nice, you can now install Lion via your hopefully working network, as well as wiping the badness from your drive.

This sucks, since you probably did not save the download.

Really, you want to get a copy of Lion on a USB key.

  1. Applications > Install Lion > show package contents > find and mount the InstallESD file.

  2. Break out one of your many 16 gig USB keys and erase it. You're going to restore the InstallESD image onto the USB Key.

  3. Check with diskutil, the gui in Lion is sexy, but underneath is a sea of malloc(3)-y kernel panics. It needs to be bootable.

  4. It' won't boot. Thats OK, use the Recovery Partition ( cmd R on boot ) and set the USB key as your startup disk.

  5. Reboot. Try not to think about how you swore this time you'd wait until .1.

You should be back in what looks like the same place, except it should be from your USB key, which can install lion onto the wiped hard drive.

I shall attempt this last part right now, all I want is the oblivion of the zeroes ... perhaps my tinkering with snow leopard was the problem. BAH.

Very useful debugging stuff. Why is it "secret?" Why indeed? https://developer.apple.com/library/mac/#technotes/tn2124/_index.html

 man sysdiagnose

Super cool tool. I'll use it instead of watching the 14 gigs... ok enough. It is a cool tool though.


man -k diag

shows you the equally nifty mddiagnose for spotlight and tmdiagnose for time machine,

Yet not sysdiagnose.

Good luck.

EDIT: This actually did work quite well for me, the usb key even booted my lappy, and I only forgot to save Xcode, which is going on the key right now.

I'm seeing far less kernel panics, which is promising. Hope it works out for you.

  • Neither of these responses answered the question - If you already have Lion installed, but it is causing problems or is corrupted, how do you re-install Lion WITHOUT erasing your installed applications and data? – user17086 Jan 14 '12 at 21:22
  • 1
    You just re-install it over top. Just don't erase the drive. – chiggsy Jan 21 '12 at 3:35

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .