topic Re: Erasing the root disk.. in Operating System - HP-UX

Erasing the root disk..

Chris Fadrowski — Thu, 22 Dec 2005 08:22:43 GMT

I am getting rid of an HPUX server. I would like to know how to completely format the root drive.

situation;

i have two 18 gb drives mirrored.
Need to format them so no data exists
server will be sold to a reseller.

Mediainit? or DD? please help.

Re: Erasing the root disk..

Peter Godron — Thu, 22 Dec 2005 08:27:27 GMT

Chris,
I'd go for dd as mediainit has been slow for me. dd if=/dev/zero of=/dev/dsk/cXXdXXtX
This should to the trick for normal standard data sensitivity.

Re: Erasing the root disk..

Pete Randall — Thu, 22 Dec 2005 08:27:52 GMT

Popular options include re-installing the OS, running dd against it, running pvcreate -f, or mediainit. Any of the above will work, it just depends on how sensitive the data is on the disk and how cautious you need/want to be.

To my way of thinking, there shouldn't be any sensitive data on the root disk anyway.

Pete

Re: Erasing the root disk..

Gavin Clarke — Thu, 22 Dec 2005 08:30:49 GMT

Here is a similar post (from a search):

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=964689

It seems to me that dd is the favourite, being faster but still good enough.

I thought pvcreate would make data irretrievable, the post above says otherwise.

Cheers.

Re: Erasing the root disk..

Chris Fadrowski — Thu, 22 Dec 2005 08:33:00 GMT

I wasn't sure DD would work on the "root" disks. I did try that yesterday and it never finished. I let it run for over 26 hours.

Re: Erasing the root disk..

Pete Randall — Thu, 22 Dec 2005 08:45:23 GMT

I would think dd would work up until it overwrites the dd binary itself. After that, I'm not sure what would happen. Did you specify a blocksize:

dd if=/dev/zero of=/dev/rdsk/c0t6d0 bs=1024k

It's true that pvcreate won't actually destroy any data on the disk but it makes it darn hard for anyone to recover unless they knew the layout of the disk to start with. Even destructive methods like dd and mediainit leave data behind that the determined snoop can get at.

Pete

Re: Erasing the root disk..

Gavin Clarke — Thu, 22 Dec 2005 08:49:02 GMT

Seems like re-installing the OS is the best way now then.

I do agree with Pete that there is/should be very little to get rid of on the root disks, still better to be safe I guess.

What was the block size you used?

Re: Erasing the root disk..

Chris Fadrowski — Thu, 22 Dec 2005 08:51:23 GMT

I used bs=512

It never finished. I just killed it, and i can still see all files on vg00 like it did nothing.

Re: Erasing the root disk..

Gavin Clarke — Thu, 22 Dec 2005 08:56:00 GMT

That post suggests bs=1024k, which is quite alot different I think.

The kernel is running in memory so I would think it should be able to overwrite it's own files before it died.

Re: Erasing the root disk..

Pete Randall — Thu, 22 Dec 2005 08:59:30 GMT

Chris,

512 is the default and writes out 512 byte blocks - it will definitely take forever. Try it with 1024k.

Pete

Re: Erasing the root disk..

Gavin Clarke — Thu, 22 Dec 2005 09:02:44 GMT

Pete, sorry for the duplication, I didn't see your post before I submitted mine.

Cheers.

Re: Erasing the root disk..

Geoff Wild — Thu, 22 Dec 2005 09:42:02 GMT

Even doing a rm -rf / will render the OS inoperable...

Rgds...Geoff

Re: Erasing the root disk..

Cem Tugrul — Thu, 22 Dec 2005 10:01:48 GMT

Chris,
if i were you i would prefer re-install OS
Good Luck,

Re: Erasing the root disk..

Chris Fadrowski — Thu, 22 Dec 2005 13:59:23 GMT

the DD doesn't seem to work.

i will most likely try to reinstall the OS.

Re: Erasing the root disk..

James R. Ferguson — Thu, 22 Dec 2005 14:12:06 GMT

Hi Chris:

As msntioned, vg00 probably has only a few "significant" files on it that you don't want seen.

Consider removing or modifiy those. For example, you could eliminate all account information and $HOME directories; reduce the '/etc/hosts' file to a minimum; and remove network information from '/etc/rc.config.d/netconf', etc.

Short of physically destroying the disk, you would need to overwrite it 10-20 times to truly make it unreadable.

Regards!

...JRF...

Re: Erasing the root disk..

Patrick Wallek — Thu, 22 Dec 2005 14:16:56 GMT

My preferred method for this is to use 'dd' to wipe the data disks on the system.

Then I do a BASE HP-UX install to one of the data disks, without doing any additoinal software, customizations, etc., and then use dd from that install to wipe the original OS disks.

Re: Erasing the root disk..

Doug Burton — Thu, 22 Dec 2005 14:38:27 GMT

You stated that dd didn't work. Did you have /dev/zero? Some of the older-ish boxes don't seem to have it. If you don't have it do the following...

Do we have /dev/zero? ll /dev/zero
If not then create one:

For 11.xx:
mknod /dev/zero c 3 0x000004 ; chown bin:bin /dev/zero ; chmod 666 /dev/zero

For 10.20:
mknod /dev/zero c 3 0x000003 ; chown bin:bin /dev/zero ; chmod 666 /dev/zero

Then wipe all the drives:

for x in `ls /dev/rdsk`
do
dd if=/dev/zero of=/dev/rdsk/${x} bs=1024k &
done