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I have used shred on my HDD, but in the middle of that, I used Ctrl+C combination accidentally. After that I noticed bad sectors on Disk Assessment. I am using Linux mint 18 as my OS.

Using fsck, I tried to fix the broken sectors. I have rebooted the system , again I can see bad sectors on Disk Assessment

After I while I formatted my HD with zeros. After that the broken sectors got increased. I ran SMART, both short and long DST got passed. Still I can see bad sectors on Disk Assessment.

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    Your disk is dying. Buy a new one, be happy the old one didn't crash while you still had useful data on it, and reconsider the amount of faith you put in SMART (i.e. SMART can sometimes tell you that your disk is dying; it can't reliably tell you that your disk is ok). – Satō Katsura Nov 1 '16 at 7:04
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Difficult to say without seeing the actual SMART output, but many disks have broken sectors, which are flagged as soon as they are discovered. They are discovered when accessing them, so writing zeroes to your harddisk can increase the bad sector count (but the sectors have already been bad before).

It's next to impossible to create bad sectors by interrupting a command (with ctrl-c, or otherwise). It's also not possible not "fix" bad sectors using fsck.

You can force remapping of bad sectors by writing to them (e.g. dd with correct sector address), which you already did using shred. But given you want to shred the disk anyway, there's no need to fix anything.

If you are really paranoid about the data on your disk, shred it physically (open it up, use an axe, strong magenet, or whatever).

  • I was about to take the laptop to a service center to fix a keyboard issue actually. Before that I thought of shredding the data. I doubt that it is logical damage to the disk. Could you please give me some idea about the force remapping? – dasrohith Nov 1 '16 at 7:03
  • Writing zeroes to all sectors should be all you need, the service center isn't going to have an electron microscope to recover data on bad sectors, nor will they invest the effort just for fun. I'm not sure what you mean by "logical damage". And yes, the bad sectors will stay bad, even after they get remapped. Depending on what SMART says, you may want to get a new harddisk, if it's too many bad sectors. – dirkt Nov 1 '16 at 7:09
  • I was referring to this answer askubuntu.com/a/550448/395017 . But I was not able to see any bad blocks. This confused me again – dasrohith Nov 1 '16 at 8:15
  • There are two machinisms to hadle bad blocks: By the (1) harddisk itself, and by the (2) ext filesystem. (1) The harddisk can reallocate blocks ("use block 456 whenever the computer access block 123, because block 123 is bad"), and the number of those reallocations is shown in Reallocated_Sector_Ct. All of these were bad sectors originally. (2) The filesystem can ignore blocks that are known to be bad. If the harddisk itself can reallocate bad blocks anyway, using this feature is a bad idea, so usually this list should be left empty. – dirkt Nov 1 '16 at 8:35
  • Sorry for asking more questions to your answers @dirkt. The badblocks command give me 0 bad block. Whether it means that my HD doesn't contain any bad sectors? – dasrohith Nov 1 '16 at 9:34

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