[SOLVED] Will the following dd command completely erase my hdd?

hddfsck · 09-05-2019, 05:25 AM

"# echo "warning, this ERASES everything on this drive."

"# dd if=/dev/zero of=/dev/sdx count=8196"?

I don't know how the 'count=8196' was derived.

Thanks.

jsbjsb001 · 09-05-2019, 05:30 AM

hddfsck · 09-05-2019, 05:43 AM

Quote:

Originally Posted by jsbjsb001

Yes

Thanks. I know to delete everything including every piece of malware on a hdd, there is software made by the company Blancco which works 100%; don't believe there is anything out there that can compete with it, including dban. It is able to open locked areas, etc.; I don't remember all the details.

How would you compare this dd command to blancco, if you had to guess?

Thank you!

Firerat · 09-05-2019, 05:44 AM

well
yes and no

That command is copying 512 bytes ( dd's defaul; block size ) of "nothing" 8196 times to the drive in sequence.

so the first 4 mb of the drive will be "blank"
It will look "empty" but with some work the data could be retrieved.

hddfsck · 09-05-2019, 05:46 AM

Quote:

Originally Posted by Firerat

well
yes and no

That command is copying 512 bytes ( dd's defaul; block size ) of "nothing" 8196 times to the drive in sequence.

so the first 4 mb of the drive will be "blank"
It will look "empty" but with some work the data could be retrieved.

Thanks. Should I change the count size?

Firerat · 09-05-2019, 05:58 AM

it really depends on what you want to achieve

I see mention of malware ( I didn't see that post before I made mine )

if you wanted to get rid of that,, it would depend on the malware and how sophisticated it is.

you could completely fill the drive with random, then repeat a few times.
I don't know blancco , it is probably doing something similar to that.
does it take a while?

dc.901 · 09-05-2019, 06:01 AM

Quote:

Originally Posted by hddfsck

Thanks. Should I change the count size?

From dd man page:

Quote:

count=N
copy only N input blocks

So, as mentioned; it depends on what you want.
If you want to write zeros' to the whole drive, then just use dd command without count.
When it reaches the end, you will see message similar to "no space left on device".

hddfsck · 09-05-2019, 06:13 AM

Quote:

Originally Posted by Firerat

it really depends on what you want to achieve

I see mention of malware ( I didn't see that post before I made mine )

if you wanted to get rid of that,, it would depend on the malware and how sophisticated it is.

you could completely fill the drive with random, then repeat a few times.
I don't know blancco , it is probably doing something similar to that.
does it take a while?

Yes, blancco takes about 8-12 hours for a 1TB hdd. It is used around the world to clean hospital drives, financial places, etc.

hddfsck · 09-05-2019, 06:15 AM

Quote:

Originally Posted by dc.901

From dd man page:

So, as mentioned; it depends on what you want.
If you want to write zeros' to the whole drive, then just use dd command without count.
When it reaches the end, you will see message similar to "no space left on device".

In this case, it doesn't matter if it can be gotten to later since there will be a lot of duplicate data anyway. For one drive I just need to get rid of it so I can encrpypt the partition and then add data. So the faster the better, in this case. Thanks.

Firerat · 09-05-2019, 06:24 AM

Quote:

Originally Posted by hddfsck

In this case, it doesn't matter if it can be gotten to later since there will be a lot of duplicate data anyway. For one drive I just need to get rid of it so I can encrpypt the partition and then add data. So the faster the better, in this case. Thanks.

in that case
the dd in the OP will be fine
/!\ do make sure you are writing to the correct drive /!\

Personally I would just delete the existing partitions with the partition manager I would be using to create the partitions for the encrypted drive.

jsbjsb001 · 09-05-2019, 06:39 AM

Sorry hddfsck, I should have been more clear than what I was. The command in your OP would zero out the MBR partition table, or in the case of GPT partitioning, the header that points to where it is (from my understanding of GPT partitioning). Therefore that would effectively "erase" the drive as far as the system's concerned as said above - that's what I should have said.

In any case, why not just format whatever partitions you have on the drive if you don't care about the data on it?

hddfsck · 09-10-2019, 02:32 AM

Thanks to all.