How can i be sure that all the rubbish has gone?

Discussion in 'Mac Basics and Help' started by *old-guy*, Dec 20, 2008.

  1. *old-guy* macrumors regular

    Nov 22, 2007
    Blackburn in North West England
    Hi all,
    I'm almost a new guy in Mactown and I'm looking for a bit of advice re deleted files. Windows users seem to say that files that get deleted never actually go away, otherwise, how would the folk who make money by recovering deleted files make any money?
    So here I am with an eMac and Tiger + all the extra junk I have downloaded from the web or installed from disk. Gigs and gigs and gigs of it. What I would like some kind person to explain is this, if I now decide that I know which bits of software I want on my Mac, how can I be absolutely sure that all the stuff I don't want is totally out of there when I start from scratch with a fresh install of 10.4? Will a fresh install remove all those sneaky little bits left behind by some software? `no names, no pack drill but AOL is a sod for that kind of thing if I recall correctly.

    Cheers m'dears.
  2. old-wiz macrumors G3

    Mar 26, 2008
    West Suburban Boston Ma
    Almost all file systems by default do not erase file content when you delete the file and empty trash. All that the file systems do is mark the space for the file name in the disk directory as "available" and return the space used to the free allocation table. There are utilities that can recover, but it's touchy. Some file systems offer an option to wipe files when you delete them, but it takes extra time. Disk utilities can be set up to wipe free space. You could do a fresh install, but you would need to first wipe the disk with disk utility. Normally even a fresh install does NOT wipe the disk of previous data if the area is marked 'available'. Thus even a fresh install would still leave the old data there, but it would not be accessible to normal file system use.
  3. Dark Dragoon macrumors 6502a

    Dark Dragoon

    Jul 28, 2006
    An easy way to think about it is to imagine your hard drive is a video tape and you keep a record of what has been recorded onto the tape in a book.

    When you record something you write an entry in the book including where to find the recording so you can find it later.

    When you are no longer interested in the recording you cross it through or remove it from the list of recordings in the book, as far as the book is concerned the space is now empty, and is free to have something else recorded on.

    However even though you have crossed through the entry in the book the space on the tape will still contain the recording, until it is actually recorded over.

    This is basically the same way a hard drive works and is not something that most people will need to worry about, unless they are trying to remove sensitive data. There is one difference though, due to the way hard drives work it is still possible to recover the old data after it has been written over.

    If you do a clean install (format the drive) you do not need to worry about files being left over from previous installations, unless you have sensitive data.
  4. MrChurchyard macrumors member

    Sep 22, 2008
    Delete the files in the Finder, then click on Finder/Secure Empty Trash. Or go into the Finder preferences, go to the "Advanced" tab and check "Empty Trash securely". This will overwrite the space on your hard drive where the files had been with junk (like only zeros) so that the files cannot be brought back.

    Or, to be really thorough, use Disk Utility from an external booting device, then "Erase" the HD in question after setting the Security Options accordingly ("3 If you want to prevent the recovery of the disk's erased data, click Security Options").

  5. Ashka macrumors 6502a


    Aug 9, 2008
    New Zealand
    Erasing free disc space with Disc Utility will clean up the space left by deleted files & folders. It can write zeros all over the space 7 or 35 times. :cool:

    You don't have to reinstall as it works around the files in use.
  6. BlueRevolution macrumors 603


    Jul 26, 2004
    Montreal, QC
    If this is something you plan to do regularly, I suggest instead enabling the "Empty Trash securely" option in Finder as MrChurchyard mentioned. It will zero out deleted files, making it unnecessary to erase free space after the fact, and will do so immediately.
  7. KingYaba macrumors 68040


    Aug 7, 2005
    Up the irons
    Definitely enable it via Finder's preferences, but give Disk Utility a go once more after you enable this feature. But as a precaution, do zero out a drive if you're prepping a machine for sale.
  8. *old-guy* thread starter macrumors regular

    Nov 22, 2007
    Blackburn in North West England
    Ah, I think I may have given the wrong idea.
    There is nothing of an iffy nature on the hard drive. No donkey/kitten porn :D
    What I want to make sure has totally gone, and therefore not taking up any space at all, is like when I saw a freebie photo editor or things like that. I tried them, didn't like them and so got rid of them. I just wanted to be certain that they had actually been removed with no bits left behind.
  9. eluk macrumors 6502a


    Dec 14, 2006
    East London, UK
  10. rdowns macrumors Penryn


    Jul 11, 2003
    If you're doing a clean install of the OS, there will be nothing left behind.

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