topic No /dev/urandom in Operating System - HP-UX

No /dev/urandom

TYP3R — Mon, 02 Jul 2007 03:58:49 GMT

HI Guru's

I'm, having trouble with the following:

#/dev/urandom of=/dev/rdsk/c#t#d# bs=512k conv=noerror

I get /dev/urandom: No such file or directory

Do i need to create a directory with the /dev/urandom file init ? With the same principles with the /dev/zero ? eg:

#mknod /dev/urandom c 3 0x00003
#chmod 444 /dev/urandom

If soo how can this actually write in random instead of the begining to end of disk ?

Thanks for the help

Will

Re: No /dev/urandom

Luk Vandenbussche — Mon, 02 Jul 2007 04:44:43 GMT

Will,

I don't know what you are trying to do, but
/dev/urandon cann't be used as a command.

Possible there is a mistake in the output of your command?

Re: No /dev/urandom

TYP3R — Mon, 02 Jul 2007 04:56:09 GMT

Hi Luk

I got this from this thread:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=972440

I know that i can use this command:

dd if=/dev/zero of=/dev/rdsk/c#t#d# bs=512k

But i assume that the /dev/urandom will write 0's all over the disk randomly ( Like a butterfly effect) than from beging to end, But i get an I/O error with the /dev/zero comamnd, Is there a way to get rid of the error as oseek=1 or conv=noerror doesnt work

Will

Re: No /dev/urandom

Steven E. Protter — Mon, 02 Jul 2007 05:00:44 GMT

Shalom,

With HP-UX 11.11, you may need to install the strong randome number generator to accomplish this task.

http://h20293.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=KRNG11I
Reboot required

SEP

Re: No /dev/urandom

Dennis Handly — Mon, 02 Jul 2007 05:06:51 GMT

>Luk: /dev/urandon can't be used as a command.

I believe it was:
# dd if=/dev/urandom of=/dev/rdsk/c#t#d# bs=512k conv=noerror

Re: No /dev/urandom

TYP3R — Mon, 02 Jul 2007 05:21:15 GMT

HI SEP

Thanks for the link but after i've read it, Its not what i really want, All i want is to write zero randomly across the disk ( Butterfly Effect) with the command:

dd if=/dev/zero of=/dev/rdsk/c#t#d# bs=512k

Instead of writing zero from start-end of the disk.

Is this possible at all ? or am i been to picky on the way it writes zero on the disk ?

Will

Re: No /dev/urandom

Dennis Handly — Mon, 02 Jul 2007 05:32:28 GMT

>All i want is to write zero randomly across the disk (Butterfly Effect)

Do you want to shake the disk apart?
Can you say why you want to do this?

>Is this possible at all?

Only if your write your own application.

Re: No /dev/urandom

TYP3R — Mon, 02 Jul 2007 06:13:45 GMT

Dennis

It just that a customer want us to write zeros to a disk in that way

Will

Re: No /dev/urandom

Dennis Handly — Mon, 02 Jul 2007 06:55:03 GMT

>It just that a customer want us to write zeros to a disk in that way

Is he trying to destroy the data on the disks?

Re: No /dev/urandom

TYP3R — Mon, 02 Jul 2007 13:29:47 GMT

Well Dennis if you read what i want to do,

Writing zeros do destroy the data on the disk.

If you not going to help me out then stop moaning what other people saying as they are trying to help me out unlike you.

Re: No /dev/urandom

Hein van den Heuvel — Mon, 02 Jul 2007 14:45:37 GMT

Interesting...

>> Well Dennis if you read what i want to do,

Dennis read what you want to do, but is one step ahead of you, which you fail to see/accept.
He, like most of the folks here reading your question, realizes that you are on a wrong tangent and wants to help you with the true problem behind the question.

>> Writing zeros do destroy the data on the disk.

Then you should just use /dev/zero and let'r rip. By writting chunks of zeroes at random place you may will destroy some data, but not all. That will make it harder to figure out what was on the disk, bight might not make it impossible.

There are many, many prior topics on 'destroying' data on a disk. Just google.

>> If you not going to help me out then stop moaning what other people saying as they are trying to help me out unlike you.

He is trying to help better than the others by addressing the real problem vs the perceived problem.

>> All I want is to write zero randomly across the disk

Then you would need to randomly change the optional 'oseek' argument value for the dd command to create an 'Output Seek'.

The 'if' argument is the Input File and by providing /dev/zero this will give an infinited stream of buffers of zeroes, where a /dev/random would provide a stream of buffers of random data... but the dd command will just write those out one after the other, not in a random place. You'd be getting random data in a predictable place.

Cheers,
Hein.

Re: No /dev/urandom

OldSchool — Mon, 02 Jul 2007 14:53:06 GMT

"But i assume that the /dev/urandom will write 0's all over the disk randomly ( Like a butterfly effect) than from beging to end..."

nope. its going to write a random number from beginning to end, not 0's randomly across the disk.

as noted in the other thread you noted, pvcreate + multiple passes are a viable alternative.