topic Re: Using dd command for wiping disks in Operating System - HP-UX

Using dd command for wiping disks

Joanne Joki_1 — Mon, 05 Aug 2002 21:13:26 GMT

We are trying to decommssin our K200. When we enter the following command:

dd if=/dev/zero of=/dev/rdsk/(somedisk) bs=1024

the system goes off and appears to be wiping the disks (the light is on and stays on) but it NEVER returns to prompt. What are we doing wrong?

Re: Using dd command for wiping disks

harry d brown jr — Mon, 05 Aug 2002 21:34:51 GMT

here are some hints:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xa5c60bce6f33d6118fff0090279cd0f9,00.html

I usually use a "count"

live free or die
harry

Re: Using dd command for wiping disks

T G Manikandan — Tue, 06 Aug 2002 04:04:50 GMT

Also check this one

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x3c0f36e69499d611abdb0090277a778c,00.html

Thanks

Re: Using dd command for wiping disks

Pete Randall — Tue, 06 Aug 2002 10:10:46 GMT

Joanne,

Your block size is only 1024 bytes. That's going to take forever. Try 1024k instead.

Pete

Re: Using dd command for wiping disks

Cheryl Griffin — Tue, 06 Aug 2002 10:54:06 GMT

The speed also depends on the size of disk. How large are the disks? Increasing bs as mentioned before will help.

Verify your /dev/zero file has the correct major/minor number. Otherwise nulls may be written instead of zeros.

At 10.20 (minor was 3)
# mknod /dev/zero c 3 0x000003

At 11.00 (minor has to be 4)
# mknod /dev/zero c 3 4 /dev/zero
# ll /dev/zero
crw-rw-rw- 1 bin sys 3 0x000004 Aug 2 2002 /dev/zero

At 11i, insf should create this file automatically, if it doesn't already exist.

Best Wishes,
Cheryl

Re: Using dd command for wiping disks

Stefan Farrelly — Tue, 06 Aug 2002 11:00:43 GMT

There was a long discussion about this a while ago. Heres the link.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x24b53a7b3682d611abdb0090277a778c,00.html

The best way is to not only use /dev/zero but /dev/one, two... etc. There is a perl script on the above link to do random writes of 1's, 2's etc.

Re: Using dd command for wiping disks

Hai Nguyen_1 — Tue, 06 Aug 2002 11:14:31 GMT

Joanne,

Pete is correct. I myself always use bs=4096k.

Hai

Re: Using dd command for wiping disks

Sanjay_6 — Tue, 06 Aug 2002 12:36:52 GMT

Hi,

Either increase the block size or stay patient. It takes some time to do the dd, depending on the size of the disk. try,

dd if=/dev/null of=/dev/rdsk/cxtydz bs=1024k

Hope this helps.

Regds

Re: Using dd command for wiping disks

Joanne Joki_1 — Tue, 06 Aug 2002 14:09:20 GMT

thanks, all. The size of some of the disks are 2gig and some are 4gig. I will try increasing the block size and see if this helps. The minor number was set to three per the instructions I got from HP -- is this going to be a major problem?