wiping of unused space on ext3

Matt Stegman matts at ksu.edu
Thu Sep 7 22:40:26 UTC 2006


Well, the manpage does say:

BUGS AND LIMITATIONS
       The `c', 's', and `u' attributes are not honored by the ext2 and
       ext3 filesystems  as implemented  in the current  mainline Linux
       kernels.  These attributes may be implemented in future versions
       ext2 and ext3.

If I remember right, it was dropped from the kernel because it was
incomplete - inode data isn't wiped, the journal isn't wiped, and if a
file is truncated, old data blocks weren't wiped.  I think these were
decided to be too difficult or too slow to implement, and so the feature
was dropped "for the time being."  It's been a while since I read the mail
thread on this though, and my memory may be faulty.

-- 
Matt Stegman

On Thu, 7 Sep 2006, Wolber, Richard C wrote:

> > On Sep 07, 2006  07:53 -0700, Wolber, Richard C wrote:
> > > I believe you can use the "chattr -s" command to mark all
> > > of the files so that when they are deleted, their blocks
> > > are wiped with zeros.
> >
> > In theory yes, but this has never been implemented.
>
> *BLINK*
>
> So let me get this straight. This feature is documented
> in the man page and works within the chattr command. It is
> also noted when you do a "chattr -v". And yet it still has no
> effect? I seriously wonder how many people are using this
> "feature" without realizing that it has absolutely no
> effect?
>
> Is it worth my time to patch the documentation? Or is this the
> forgotten stepchild of a development dispute that the parties
> would ignore any sane input on?
>
> ..Chuck..
>
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