How to do go about completely erasing a disk? I have to return school pc and I want to be sure there's no personal data on it

@dottorblaster @SonoMichele
And read from /dev/null when using dd. And you might choose dd_rescue as it shows progress.

@SonoMichele @dottorblaster
DD has an input file and an output file. /dev/null is a pseudo file that gives you as many zeroes as you want in highest speed. That means the only slow down is due to the (output) disk you want to erase.


@dottorblaster @rudolf @SonoMichele

Everything that @rudolf said is true, but there are a bunch of caveats that I think need to be mentioned.

First, dd itself. Feel free to search for this, but dd is basically unnecessary for this operation, you can do cat > /dev/sdX and that will work just as well- and usually much faster. The only reason for DD is essentially historical.

But that's not really important, what's important is that disks aren't really disks anymore...


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@dottorblaster @rudolf @SonoMichele

Back in the old days, you could write bytes to a disk and they would go onto the disk. But now a days, disks are complex things with multiple layers of abstraction to even the OS. There's a caching layer, an automatic error detection layer, etc.

And on an SD drive, forget it... you aren't really talking to anything real.

Because of that, yes you can write all the nulls to the disk and that will stop a casual snooper but not a sophisticated one.


@dottorblaster @rudolf @SonoMichele

For spinning rust drives, look at tools like GNU shred. Or at the very least, run the cat /dev/null or /dev/zero command multiple times.

For SSDs, look at more complex methods that sure your data is unrecoverable.

For a school return, this is admittedly probably unnecessary but these are good habits to get into. :)


@emacsen @rudolf @SonoMichele wow, a lot of information, I was stuck to the old fashioned but you really gave me material to study, thank you so much

@emacsen @dottorblaster @rudolf thanks for all the information. I didn’t know it became so hard to wipe an ssd

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