Originally Posted by John VV
for wiping free space what is wrong with the built in "shred" and "dd"
--- should work ---
dd if=/dev/null of=/oneBigFile.bin
shred -n 1 -zv /oneBigFile.bin
i just use one of my 5+ gig size planet maps / data sets and copy/paste them over and over to fill up the drive.
I am not an expert. I have been reading stuff all day.
Also the man pages. There are warnings that ext3 cannot be reliably wiped with any file shred or srm, apparently, and I am not sure of this, because sometimes it does not write over exactly the same bits for the whole file. I am not sure of that. I was sure on Win 98, because I studied it with Norton's diskedit.
I am trying to sort this out now.
But, whatever is the exact reason, all the papers and boards I read said that on ext3, plus some ntfs systems, one cannot trust it.
sfill was created to answer all these issues. The only thing sfill can't do is fill the slack space which in some cases is filled with previous data, even random RAM data. sfill does not take care of this slack space, at least I don't think so. I did bump into one proprietary utility, which cost money, which did wipe the slack space on Windows systems.
I am also not sure about the Big File over-write. I have read over the years the reason there is no significant fragmentation in Linux is because the files are stored first in available areas big enough to hold the entire file. If that is true, and I do not know it is, then small files which have been deleted will not be written to, period. It will first look for a very large space.
Windows 98, or DOS, I am starting to forget, after booting will put the first cluster of a file on the first free cluster, then look for the next available cluster, for the second cluster to be stored. You can see this is why there is a tremendous amount of fragmentation on a MS HD.
As I said I do not know to my satisfaction if it is true a big file is going into a big hole, instead of strewing it all over the disk as windows (did).
I would like to make it clear that I wish I had much more information than I do.
I am going, IF I HAVE TIME, to do some work with hexedit and file saves, etc. This is important to me, if only because I am a curious cuss.
I will say with certainty that if this is important to you, do not assume anything, because it may well not be correct.