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I have recently upgraded to a 2011 MBP, and I'm finally all set up on it. It's time to sell my previous MBP. I've already copied off all of the data I want to keep and deleted the obvious suspects.

What is the preferred approach to prepping a used Mac to be sold to an unknown third party that does not include a complete wipe and reinstall?
If possible, I'd like to leave the activated programs on it. (Perhaps, that is a horrible idea and contrary to prepping for resale.)
Is it enough to create a new user, log in as that user and delete the previous user?

I apologize for the basic question; I realize the nuclear option is probably the recommendation, but I'm thinking it would help my resell value to leave the activated software in place.

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    Do consider two things. If you are selling a machine to someone without the media to reinstall and properly own that app - what happens if they have a crash or make a mistake? Do the right thing by making really sure the buyer understands exactly what they are getting. Also think about doing the right thing by the people that made the software you are selling. Any software you bought almost certainly has a license calling out what you are supposed to do in this case. Check with a lawyer if you're not sure what you own and what you only have a license to use.
    – bmike
    Jun 1, 2011 at 19:38
  • @bmike considering the licensing and recovery points you make here, it is clear that trying to "bundle" the installed software is wrong. With this in mind, I'll accept @petruza's answer since it provides the clearest approach to erasing data :-) Jun 2, 2011 at 3:17
  • :-) @petruza's answer is very good - glad you have lots to choose from. You can always sell the original OS CD and bundled software with the mac. Just don't keep a copy for yourself and you're fine.
    – bmike
    Jun 2, 2011 at 18:02
  • @bmike "Check with a lawyer"? Seriously?
    – endolith
    Dec 6, 2014 at 1:59

8 Answers 8

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If you are really concerned with the next owner recovering your files, which can be done even if you emptied the Trash, then you should format the drive:
Open Disk utility, select the drive, select the erase tab and click on security options, then choose one othe following:

enter image description here

I don't know why the sale doesn't include a wipe and reinstall, but I don't see why it shouldn't as a mac always comes with a licensed OS, you just format the drive and reinstall MacOS and you're done.

You can't erase the drive you are currently booted to. You have to boot from an external drive with Mac OS X installed, or boot from the Install DVD.

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You should wipe and reinstall. Reasons:

  • personal info. Anybody can attach your Mac in target disc mode and copy the whole HDD for later analysis. Even if a file is removed by emptying the Trash, or via the "rm" unix command, there is a possibility to recover it (because it deleted only the reference to HDD sectors and not wiped the sectors).

  • applications - If you have any applications, you probably want to use them later too. If you sold the MacBook with them, the buyer will use them too - double install usually means disabling your legal activation key.

  • with clean reinstall, you delete everything - for example /Library/Application support too, where much applications saving some infos (non personal, but anyway).

  • another example - the logfiles in the /var/log directory. Here are tons of informations that can be gained from them (for example mail addresses) and so on...

  • erasing the Home directory is simply not enough (see above).

  • as @Petruza already said - the only way is to wipe the whole HDD and reinstall the OS X.

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  • Good points on the logfile database. I don't know if any of my mac have ever logged an email address (I just checked several) but mobile me acccount names and other things are certainly logged by default. Whatever method of wiping you prefer before a reinstall can also be done as srm and erase free space in Disk Utility. I guess it's a personal call - is it faster for you to clean around the apps you wish to leave, or wipe once and reinstall / update those apps. I can see how one is faster for some but no universal best option.
    – bmike
    Jun 1, 2011 at 19:09
  • /var/log/maillog - logging email recepients but only when using internal smtp. (not a common case - but anyway) :)
    – clt60
    Jun 1, 2011 at 21:22
  • Shazam! didn't even think of setting up smtp. It goes to show how complicated logging can be - especially with the new log databases and not the old flat files of yore.
    – bmike
    Jun 1, 2011 at 21:44
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    Thanks for your response, this is the kind of information I was originally seeking, but I've been convinced that wiping the machine is the best choice since "bundling" my installed applications was a bad idea for several reasons... Jun 2, 2011 at 3:18
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After creating new user and deleting the old one, at least wipe free space to remove securely your data. However, a lot of data can be retrieved from remaining (for example temporary) files. So that the only secure option is full wipe. And remember to unpair your hardware from any other devices/network services (Bluetooth, MAC address etc).

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You can erase your hard drive by putting in your Mac OS X Install DVD, and boot from there. Then when that boots up go to Disk Utility under Utilities just after you choose your language. Here is a support article from Apple on how to erase and reinstall the OS.

http://support.apple.com/kb/ht1820

It is illegal to leave software that requires user authentication on a computer you intend to sell. When you purchased that software you agreed with whatever software company that you wouldn't abuse the amount of user licenses purchased. By leaving it on your computer to "increase" the value you are abusing the software company TOS.

Plus if you copied those applications to your new computer, and if you sell your old one with the applications still authorized they can "call home" and that serial number can be flagged and all applications that are activated with that serial number can be deactivated.

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  • Perhaps this would be better commenting that most software is licensed for one user and not deleting the software from a machine you no longer posses and keeping the software might have legal consequences. Unless you or the questioner have actual legal advice appropriate for the location of the poster - the safe bet is to erase the mac and only leave software installed that you are selling with the machine.
    – bmike
    Jun 1, 2011 at 19:28
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Another user had a similar question - so do check out the answers there.

How to install apps to Snow Leopard after a fresh reinstall and still keep the MacBook in a pre-first-boot state?

In a nutshell - you can make a "test" account to delete the personal information and apps you wish to not transfer. You can then run all updates and leave things just as you wish and restore a first boot experience to the new buyer.

Do remember to deauthorize iTunes on that machine, unpair bluetooth and networks / forget network passwords. If you wish to be exceptionally thorough, you might delete old log files and crash reports. The console app will let you poke around and see if any cause you concern. I wouldn't just delete the entire directory (as some of these directories have special permissions and the system will fail in hard to realize and fix ways if the directory containing a log file is missing.) Typically the log file itself will get recreated at next boot, but the programs that maintain the files generally assume the directories have been set up properly and they won't make entire directories. Just realize you are mucking around in the bowels of the unix system my modifying or deleting these files and directories may make the mac you sell less stable or cause issues to the new owner who may be ill equipped to solve.

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  • very interesting... but to play on the safe side, I'd rather have a simple solution to zero-out as a first step.
    – cregox
    Jun 7, 2011 at 14:19
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Just to update this: since Apple started splitting the OS and user Data onto two separate disk volumes (Big Sur?), all you need to do is to erase the user data volume. (This is for T2 Intel Macs and Apple Silicon.)

In Ventura and above, there is an option in System Settings > General > Transfer and Reset to Erase All Content and Settings.

In Sonoma, there is even an "Erase Assistant" application (in /System/Library/CoreServices.)

enter image description here

The days of wiping the entire disk and re-installing the OS are over.

The Data volume contains everything that is not the OS image. So all log files, plists, databases, etc, etc.

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  • Some Macs do not have this option, even on Sonoma
    – Ezekiel
    Oct 20, 2023 at 3:27
  • @Ezekiel Really? Which ones -- Intel? I can't see why not, as they still have the Data on a separate partition.
    – benwiggy
    Oct 20, 2023 at 6:48
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    The 2019 iMacs don't have T2 chips, which is necessary for this feature. The feature doesn't just perform a delete of the Data drive, which is not secure on its own. It takes advantage of the T2/Apple Silicon encryption layer that is always on (even without File Vault) and discards the keys, which effectively scrambles the disk. Without the T2/Apple Silicon this can't be done effectively.
    – Ezekiel
    Oct 20, 2023 at 14:04
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When we sell our old macs at work on, I use a data shredder and do a clean install of the OS. Seems to work, not had any complaints so far

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Mac computers with Apple Silicon or a T2 chip, running macOS Monterey 12 or later, have an option to "Erase All Content and Settings." If you're running Monterey, the option is in System Preferences, in the menu bar under System Preferences > Erase All Content and Settings. If you're running Ventura 13 or later, the option is in System Settings under General > Transfer or Reset. Erase your Mac and reset it to factory settings

Erase All Content and Settings

Mac computers without the Erase All Content and Settings will need to perform a series of manual steps to properly ensure their data is removed and their iCloud account is disconnected. Refer to the Apple Support document linked below for those exact steps.

Source: What to do before you sell, give away, trade in, or recycle your Mac

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