Linux dd wiping security

[kalpana]

Hello,

I have some questions regarding the "dd" utility, if someone can help. Please answer only if you are sure about the answer !

I have a scenario here in which I have a HDD with Bad Sectors that I need to wipe in order to archive it.
I want to decomission that respective HDD and I started to wipe it using one-pass zeros.

Code:

Code Select Expand

dd if=/dev/zero of=/dev/sda status=progress
at exactly 3.7 GB in the Wipe (the HDD has 500 GB capacity), it always throws me a "I/O Error" and the dd utility exists.

I ASUME there is a Bad Sector or something there...

Now, I have multiple questions/issues:

1. Is there a method to WIPE ALL the sectors of that respective HDD, even if there are bad sectors ? Or at least SKIP the bad ones and continue wiping the rest of the HDD which has good sectors ?...
Using "conv=noerror" in "dd" does NOT do the trick, because, as I understand, "conv=noerror" only skips information in the "if" device (input device), not on the "of" device (output device).
I read something about ddrescue and badblocks, and so on, but I did not have a clear answer in my mind...

2. I read somewhere that "dd" is not such a great tool to wipe HDDs... To be more precise, I have heard that "dd" skips some sectors that the Harddisk may have reserved if they are bad sectors, for example.
I need "DD" to access ALL my HDD space.

What I want to say is that I use "dd" for 15 years to wipe all my hdds. Very few of them threw the "I/O Error", and those HDDs were archived and never given away, exactly because of the uncertainty of full wiping... So I did not take any chance...
However, I had HDDs which I wiped completely and which didn't threw any I/O Errors.

Is there even a remote possibility that "DD" did not Wipe everything from these HDDs ?
If I used "dd" and it went ALL THE WAY, until it threw the "No space left on device" message, can I safely asume that it wiped ALL the harddisk space ?
Or even in these conditions, are there some sectors/blocks that might have been reserved and "dd" cannot touch these ? (in which case, it is a security concern)...

Thank you !

Adam.