On Tue, Oct 27, 2009 at 04:12:54PM +0100, Jordi Espasa Clofent wrote: > to do it. Finally I've chosen a simple double-step method: > > First, > > $ dd if=/dev/urandom of=<disk_to_delete> > > and next > > $ dd if=/deb/zero of=<disk_to_delete>
I overwrite the disk 7 times with arandom, using the following command for x in `jot -s ' ' 7`; do dd if=/dev/arandom of=/dev/rDEVc bs=BLOCKSb ; done where DEV is the abbreviated disk name (for example, sd2), and where BLOCKS is the number of blocks to buffer. The speed of the operation is highly dependent on a proper choice of BLOCKS. I have used 128 with a 160GB external hard drive, and it takes approximately 16 hours to complete all 7 overwrites. You'll have to experiment to see what choice of BLOCKS is fastest on your hardware. I use arandom instead of urandom because it's slightly faster.
