hopefully simple query regarding dd

Polytropon freebsd at edvax.de
Thu Apr 13 09:26:58 UTC 2017

On Thu, 13 Apr 2017 10:03:02 +0100, tech-lists wrote:
> I couldn't find an an answer to this hopefully non-silly question and
> can't test it meself without possibly risking a hd. Basically what I
> want to know is this. Can I do this:
> dd if=/dev/ada0 of=/dev/ada0
> to refresh the disk, and *expect the outcome to be non-destructive for
> the disk*. That bit is important. By non-destructive, I mean for the
> data already on it.

Hmmm... input and output the same disk, with the default block
size of 512 byte? Maybe add bs=1m or something "more native" to
the disk in question.

But how should that "refresh" the data on the disk?

What should it be good for?

Basically it appears to be possible, but personally, I'd first
test it with a file-backed pseudodevice resembling a disk...

> Can I do this multiuser or do I need to boot to a rescue environment
> beforehand?


Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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