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Re: [LUG] quick question: wiping a disk



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On Tuesday 23 July 2002 3:20 pm, Alex Charrett wrote:
/dev/zero? tsk. /dev/random sounds much more fun to me, erm honest! :)

try generating <size of hard disk> bytes of random data from /dev/random..

/dev/random blocks when the entropy poool is empty, not only that, if you're 
running openssl/libcrypto of any sort in any daemons, prepare for it to 
block.  SSH may well have a headfit or block on new connections too, 
depending on how it's set up on your box and what eentropy gatering 
source/daemon it's configured to use.

dd'ing from /dev/random is find if you are using a small amount of data, but 
for a disk or gigbytes or even hundreds of megabytes is bad, bad, bad, unless 
it's a local desktop you dont't really care is it blocks/freezes for a bit.  
even so, dding from /sev/random will take a lot longer, especially with a few 
gigs.

iirc gnupg has a file wiping util, or take a peek at wipe.

alternativly, use /dev/zero, or /dev/urandom (which doesn't block) and run DD 
a fair few times on it.  I think i heard somewhere that given any disk, it's 
still possible to read what was on it X number of writes before, though myabe 
i just imagiend that, or it was in some really bad computer film ;)

take a look at drivers/char/random.c in the kernel source and the comments by 
theo tso for more info, or man 4 random.

~ Theo

- -- 

Theo Zourzouvillys
http://zozo.org.uk/

Q:      What do Winnie the Pooh and John the Baptist have in common?
A:      The same middle name.
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