secure deletion

[Ilmar S. Habibulin]

On Thu, 20 May 1999, Warner Losh wrote:

> There is a certain segment of the community that would use it.  If
> there was zero overhead (beyond a bit compare on unlink) when not
> used, binary compatible with current disks and a fairly clean
> implementation, then I think that there would be support for its
> inclusion.
My implementation was very simple. In order to secure ;-) delete file user
have to set special flag (bit) of inode. I think, that i can use ufs flags
field for that bit and chflags command. When i catch up situations of
unlinking file, truncaing its size, i bzero unused blocks.
While unlinking i found strange thing. I'm deleting blocks sequently from
low blkno to high. If i change this sequence back to front (?) i've go no
bzero'ed blocks at all. Maybe there is some other way of wiping blocks?


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