How to delete HDD data?

sunram · 10-12-2007, 01:20 AM

hi friends,

we are taking six server in rental (ultra,e250,etc).now return the all server.But important data stored in the HDD.we delete the all data. How to delete the data or how to delete the HDD label.

regards
sunram

vermaden · 10-12-2007, 01:38 AM

Code:

# while true; do dd < /dev/random > /dev/dsk/c0d0p0; done

Disillusionist · 10-12-2007, 02:19 AM

For best results do this from a bootable CD, otherwise the the script will get confused when the bash and dd commands get wiped.

jlliagre · 10-12-2007, 03:03 AM

Quote:

Originally Posted by vermaden

Code:

# while true; do dd < /dev/random > /dev/dsk/c0d0p0; done

1: This won't work on SPARC H/W, that should be c0d0t0s2 there.
2: This will crash the system before all the disk has been overwritten, which may be sufficient or not, as the question is self-contradictory (we delete all the data. How to delete the data ?).

vermaden · 10-12-2007, 03:21 AM

Quote:

Originally Posted by jlliagre

1: This won't work on SPARC H/W, that should be c0d0t0s2 there.
2: This will crash the system before all the disk has been overwritten, which may be sufficient or not, as the question is self-contradictory (we delete all the data. How to delete the data ?).

I generally do not use Solaris too much, so I will propably mess strict Solaris things like devices, I just wanted to show idea of how to do that.

Of course from some LiveCD, or by ataching the drive to other box ane wipe it there.

jlliagre · 10-12-2007, 07:08 PM

No problem, Solaris (SVR4 actually) device naming scheme is often tricky to understand for Linux admins.

Beware that when used from a live distro, your command will not only wipe the disk but may eventually destroy it after a (long) while, as it never ends.

Also, to have a better performance with this kind of commands better to use:
- the faster and less resource consuming /dev/urandom instead of /dev/random
- dd blocking factor to improve writing throughput

eg.

Code:

dd if=/dev/urandom of=/dev/dsk/xxxx bs=1024k

choogendyk · 10-13-2007, 09:43 AM

It's actually possible (but difficult) to recover data from files that have only been overwritten once. There are DOD standards for data obliteration and typically the data should be overwritten 7 times, with all 0's, with all 1's, with a pattern of 0101010, etc.

I observed once a situation where a couple of aspiring programmers were demonstrating their software for a software company. They were convinced to demo it on one of the companies computers. When done, they deleted and overwrote their stuff. After they left, the companies developers descended on the computer and successfully recovered the code. The aspiring programmers never got a call back to buy their work.

Lots of people actually destroy or seriously degauss drives before disposing of computers. Obviously, you can't do that, because you are dealing with rental machines that you are returning.

There was a lengthy discussion on the Sunmanagers list not too long ago that is summarized here:

http://www.sunmanagers.org/pipermail...er/005686.html

There was a more recent discussion of the same topic, but I was having trouble finding it just now. Anyway, there is also now a sourceforge project for doing this:

http://dban.sourceforge.net/

vermaden · 10-13-2007, 10:32 AM

Quote:

Originally Posted by choogendyk

It's actually possible (but difficult) to recover data from files that have only been overwritten once. There are DOD standards for data obliteration and typically the data should be overwritten 7 times, with all 0's, with all 1's, with a pattern of 0101010, etc.

Thaat is why I added infinite loop for that, while true ...

Code:

# while true; do dd < /dev/random > /dev/dsk/c0d0p0 bs=8m; done

25 times should be ok imho.

There is also Linux utility shred (gshred on FreeBSD) which does that, shreds all data from disk by /dev/zero or /dev/random, example:

Code:

# gshred --verbose --zero /dev/c0d0p0

iAlta · 10-13-2007, 10:35 AM

deleted by user