In regards to "zeroing-out" data: why are there files and folders left over after?

[spalding]

Greetings, this would be my 1st post; thank you for taking the time to view it.


This may be a rather technical question:


I am trying to completely zero out my hard drive, so that I may sell it. It is a good Seagate HDD. I understand the process of "erasing" the data pretty well, and I will here give the quick and dirty outline of what I do so there can be no confusion:

1) I hit "option" at start up chime.
2) I insert OS X download CD disc, and choose to boot from the CD.
3) I go to Disk Utility and I select my HDD and choose "erase".
4) I choose recommended "zero-out" option.
5) I erase the entire disk including all partitions.
6) I wait...
8) I am done, the disk is empty.

Here is where I am confused however.
At the bottom of the "Disk Utility" window, I am presented with all the basic information regarding my new blank "partition" on my HDD. There are various categories with corresponding data points.

The two I am confused with are thus, and it is because they read out the following data points:

Number of Folders: 3
Number of Files: 2

My question is, shouldn't there be 0 folders, and 0 files?
If not, what are these files, and why are they necessary?

I don't want there to be any data from the HDD previous life left over for obvious reasons, especially any personally identifiable data.

Is this normal? Because it also happens on my other drives, albeit a different number of folders and files. I don't understand why it would be necessary for there to be any data left over on the HDD, since it seems to me to be a primarily "hard" technology without any real need of software, at least until an OS is downloaded unto it.

Also when I choose "open disk image" from the menu bar, in order to open the partition for perusal, I can't find any folders or files on it. So what could this information be? Hidden data logs?

Thanks for your time.

 

[MacUser2525]

File system overhead/files used to determine your file system for the OS.

 

[spalding]

Thank you for your reply.

So the leftover files are essentially needed to identify new software being implemented into the HDD? Would this be the most accurate way of describing its function?

Also, if this is the case, why would there be differing numbers of files and folders corresponding to my different HDDs after full write over? If this leftover data is implemented by the "disk utility" feature in order for the partition to recognize new software, shouldn't the number of files be the same among all HDDs? Does the size of the HDD affect how many files are needed to accomplish the aforementioned task?

Or is this data somehow built into the different HDDs of different manufacturers, and is therefore variable between the different HDD manufacturers and inalienable from the HDD's system?

And then, also, is it possible to view this data?

 

[MacUser2525]

Thank you for your reply.

So the leftover files are essentially needed to identify new software being implemented into the HDD? Would this be the most accurate way of describing its function?

Also, if this is the case, why would there be differing numbers of files and folders corresponding to my different HDDs after full write over? If this leftover data is implemented by the "disk utility" feature in order for the partition to recognize new software, shouldn't the number of files be the same among all HDDs? Does the size of the HDD affect how many files are needed to accomplish the aforementioned task?

Or is this data somehow built into the different HDDs of different manufacturers, and is therefore variable between the different HDD manufacturers and inalienable from the HDD's system?

And then, also, is it possible to view this data?

It is the formatting for an Apple partitioned then formatted drive. If you want to look at it use something like below.

MacUser2525:~$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *120.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Mavericks               119.0 GB   disk0s2
   3:                 Apple_Boot Recovery HD             784.2 MB   disk0s3

Then you would need to mount the EFI partition that you see listed to look at any data that may be there.

 

[ElectricSheep]

The files and folders that you see are not "left-over" from anything. Rest assured that any information that was on the disk was destroyed when you zeroed it.

The thing is, as soon as a volume is formatted as HFS+ and then mounted, MacOS X creates a number of hidden supporting structures which account for the files and folder counts that you see in Disk Utility. You can get a detailed list of them by using the du -a command in the Terminal with super-user permissions:

sudo du -a /Volumes/<the volume you erased>

.

You should see listing for things like .Trashes, .fseventsd, and .Spotlight-V100. These were all created as soon as the disk was mounted and do not contain any previous information.

 

[spalding]

Okay, thanks for your posts. I am beginning to be presented with a much clearer picture now.