I am getting ready to sell my older Mac Book Air with a SSD. I would like to erase all free space on the drive to assure that any confidential data I hadn't securely deleted earlier is not recoverable. In my most recent cleanup, I moved all my own files and installed apps to the trash and attempted to empty the trash securely. When the number of files to be removed was down to 30,000 (from neaerly 100,000) it stopped securely removing them. I rebooted several times and those files were still in the trash. I attempted each time to securely empty the trash. It would pop up the progress dialog box but would immeidately close it cleaning up nothing. Finally, I switched to non-secure and emptied the Trash.
I've done to the Disk Utility, selected the SSD Drive (Macintosh HD) and selected the Erase tab. The Erase Free Space button is disabled. How can I securely clean up the free space so that whoever buys the system will not be able to recover whatever, confidential data may still be hanging around in the free disk space list?
read this article, it is outdated, but the info in it is still relevant: http://support.apple.com/kb/TA24002. Do a 7 pass erase. That conformed to the U.S. Department of Defense's security procedures until they changed their rules to that of completely destroying hard drives physically instead.