On Fri, 2009-01-16 at 22:15 +0100, Jim Meyering wrote: > How about > > --random-source=FILE > > where FILE contains a bunch of random data, > like a chunk from the middle of a well-compressed tarball? > Or even this: > > --random-source=/dev/zero
If I understand correctly, the --random-source must be as big as the data to be shredded, which makes it only useful for smallish files (a few hundred megas, at most). Certainly not effective for full disk shreds. But, if disabling the random pass is what is needed, then I guess random-source=/dev/zero would do the trick nicely, as long as a smaller number of passes is used. Example runs: Files involved: hg...@xango2:/tmp $ ls -l usr* -rw-r--r-- 1 hggdh hggdh 23921846 2009-01-16 16:07 usr.delta -rw-r--r-- 1 hggdh hggdh 71766016 2009-01-16 16:18 usr.shred hg...@xango2:/tmp $ Null random source (/dev/zero), 5 passes: hg...@xango2:/tmp $ time shred -n5 --random-source=/dev/zero usr.shred real 0m15.096s user 0m0.028s sys 0m2.380s hg...@xango2:/tmp $ Null random source (/dev/zero), default number of passes (25): hg...@xango2:/tmp $ time shred --random-source=/dev/zero usr.shred real 1m15.607s user 0m0.032s sys 0m10.453s hg...@xango2:/tmp $ Default random source (/dev/urandom), 5 passes: hg...@xango2:/tmp $ time shred -n5 usr.shred real 1m4.652s user 0m0.040s sys 0m46.315s hg...@xango2:/tmp $ Default random source, default number of passes (25): hg...@xango2:/tmp $ time shred usr.shred real 2m0.369s user 0m0.064s sys 0m53.131s hg...@xango2:/tmp Regards, ..hggdh..
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