I'm seeing a blank screen with cursor(underscore) at the top left. My laptop is accessing the hard disk continously. It's been around 15 minutes.


What command did you use? Just for the record, if you used dd without specifying a block size, it will take an eternity. If you specify a decent block size, it goes quicker.

That said, it depends on so many factors that it's impossible to give you a decent answer. (For example: Disk speed, interface type, whether there are errors on the disk, ...)

My first question is: why do you want to zero it out? If it's for your own use, just repartition. If you want to trash the disk, the most efficient way is to use a nice big hammer on the disk until its heavily damaged. That should stop most amateurs getting any data from it.

  • It had bad sectors in it. I was getting warning that disk may fail soon. So, I thought clearing it and installing OS will be good. – sushil Aug 16 '16 at 12:43
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    Nope. Trying to repair a disk that way is playing with fire, if it works at all. The disk is good for the trashbin. That's it. Do yourself a favour and get rid of it. – jawtheshark Aug 16 '16 at 12:44
  • @user3664868 the warning that the disk may fail soon refers to the hardware itself. Writing to it even more will just make it worse. – TheWanderer Aug 16 '16 at 12:54
  • Okay. I see your point. I will buy a new one. Thank you for your answers. – sushil Aug 16 '16 at 12:59

The last time I did this before selling a disc a couple of years ago, dd-ing with a 4086 byte buffer and appropriate numbers for the size of the disk, I was getting 2-3 GB/minute (there's a dd option for getting occasional progress reports, though I forget the details). So a 500GB disc would take around 200 minutes or 3 and a bit hours.

Remember, you've got to generate 500GB of data (that it's all "0" doesn't matter), then write it to the disc. If you're on a USB-2 connector, for example, you'll be limited to 480MB/sec, and 500GB @ 0.48GB/sec is a thousand seconds (18 minutes) even with nothing else happening at all.

  • It took almost 3-4 hrs and finally ended with an error that says like it was able to do 279gb to zero with speed of 25.9mb/s and input/output read,write error. I don't remember exactly but it was something like that. – sushil Aug 16 '16 at 17:55
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    You are mixing up bits and bytes. USB2 is 480Mbit/sec... 1Byte=8bits, so theoretical transfer rate of USB is 60MByte/sec. That's totally ignoring overhead. 60MByte/s means 0.06GByte/s, which means for 500GBbyte, you need 8333 seconds, also known as 2 hours and 20 minutes. Calculate in overhead and it starts getting closer to the actual results that user3664868 had. (It also matches your stated experience) – jawtheshark Aug 16 '16 at 22:55
  • Oh, and another detail. You most likely meant a buffer of 4096 bytes, which is (for this task) frankly... not enough. That's basically one sector, which won't help you that much. Just give it a bigger buffer. You've got enough memory, right. I usually use bs=1G and let it work. Too small buffer sizes with dd aren't helping as much as you'd think. – jawtheshark Aug 16 '16 at 22:56
  • Ooops, yes. Bits & bytes. Never bothered to experiment with buffer sizes much. Once I'd got something that was working OK (IIRC I did the trick of sending the dd process a signal from another terminal to force a status report), I could leave it working in a corner of the office and get on with paying work. – Rockdoctor Aug 19 '16 at 10:05

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