Mike Harris writes:
> As of ext2 fs 0.5a, the `c' and `u' attribute are not hon
> oured by the kernel code. As of the Linux 2.0 kernel, the
> 'A' attribute is not yet supported by the kernel code.
> (The noatime code is still in testing.)
>
> Well, as for "c", I know e2compr adds that support, however has
> anyone ever done patches for "u" support (undelete flag)?
There were a couple of patches for ext2 undelete, but in the end people
decided that it is possible to implement undelete in libc, so it was
better not to put this into the kernel. Whether code currently exists
to do this for a recent kernel, I'm not sure. As for e2compr, I think
code is slowly making its way into the mainstream - e2fsprogs is now
starting to have support for it...
> We now have "noatime" and "nodiratime" options in kernel. Is the
> "A" flag supported now at all?
Yes, it allows noatime to be set on an individual file basis, while
the noatime flag is for the whole filesystem.
> Does the "s" secure delete flag do anything, or is it just a
> placeholder as well?
Not currently working. There is a comment in the kernel code that shows
it existed at one time, but was removed because it made the truncate
code much more complex. Maybe it is possible to put back into the
ext2_delete_inode() function or similar VFS callback that is guaranteed
to be the sole owner of the file? I don't know - I haven't looked at it
closely.
Note that _real_ secure file deletion is much more difficult than simply
writing 0's then 1's over the data (as much as the US Government would
like you to believe this). I read a paper that suggested 27 passes of
specific byte codes + random data were necessary to even have a hope of
having the data be securely deleted.
Cheers, Andreas
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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