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How to simulate /dev/one functionality
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How to simulate /dev/one functionality

Abstract

Contents


Use of /dev/zero to write one layer of zeros is common, however we may wants three layers of garbage on the drive; layer of zero, than a layer of ones, then another layer of zeros.

Wiping Disks

# cat /dev/zero | tr '\000' '\001' | dd of=/dev/rdsk/cxxxxx bs=64k

If you are nit-picky, using <tt>'''tr '\000' '\001''''</tt> only flips 1 bit whereas a <tt>'''tr '\000' '\377''''</tt> flips every bit. There appears to be a bug in tr in that it behaves differently if reading input from a pipe. 

cat /dev/zero | tr '\0' '\377' is broken 
but 
tr '\0' '\377' < /dev/zero works perfectly (and is more efficient to boot). 


Flip bits to 1

This command should work AND flip all your bits to '1'.

tr '\0' '\377' < /dev/zero | dd bs=64k of=/dev/rdsk/cXtYdZ 

Random Data

In case that random data, instead 0s or 1s are required, the following perl code may emulate a random generator:

perl -e 'srand(time() ^ $$); while (1) { print chr(int(rand() * 255)); }' |\
dd of=/var/tmp/test.dd bs=2k count=10

Reference

PDF of forum "Wiping Disks: more than /dev/zero" : Media:Devzero.pdf

Editors/Authors

This page was last modified on 26 May 2011, at 20:37. This page has been accessed 1,435 times.