I enabled FileVault on my laptop today, and not really thinking about it selected the 'Secure Erase old home directory' option. While this is a good idea if you have really sensitive documents, I don't, and the time (not to mention abuse of the hard drive) is not worth it for me. Sadly there is no option to cancel the process once started, but it's pretty easy to do manually.
You have to do two things, first get rid of the files manually, and then restart the Secure Erase process... You will need to be in a terminal as root (in your terminal, type: sudo su - ) to do both of these things. Your previous home folder will be located in the Users directory as yourname.abunchofnumbers. Get in there and delete stuff. Make sure you are in the temporary, to be deleted directory, and not your own.. and if you are not sure, I'd stop reading here :)
hosaka:Users root# ls -l ..... drwx------+ 7 root wheel 238 Sep 7 09:30 jerrett.4700039774154735486 hosaka:Users root# cd jerrett.4700039774154735486 hosaka:Users jerrett.4700039774154735486# rm -rf Music Library Movies Downloads
You could delete everything, I just nuked all the big stuff and let the secure_erase stuff finish it up. Then you need to restart the secure_erase process. You could restart your computer to do this, but it's easier just to find and kill the process:
hosaka:Users root# ps aux | grep secure_erase root 295 9.3 0.1 2446480 1680 ?? Us 9:41AM /System/Library/CoreServices/loginwindow.app/Contents/Resources/secure_erase hosaka:Users root# kill -9 295
After this the Secure Erase process will continue, and you will get a notification telling you that the process is complete when it's done. If you did like me and only deleted the large stuff it may take a few minutes to cleanup the rest, and you can check the progress by opening the Security preference panel. Hope this helps somebody... A better option of course is to simply not click that checkbox prior to enabling FileVault :)