Solved What does the "dd if=/dev/ada0 of=/dev/ada0“ mean?

Hello everyone,

What does the " dd if=/dev/ada0 of=/dev/ada0“ mean?

The manual says:
Do a refresh of a disk drive, in order to prevent presently recoverabl read errors from progressing into unrecoverable read errors

Read data from the hard disk, then write back later?

Thanks.
 
It reads everything from ada0 and writes it back to the same device at the same place. That operation is very dangerous though to run on a live system (might be even impossible because of locking of resources by the kernel), I wouldn't do that under any circumstances unless the disk is taken offline and you have a backup that you know to be good and can be restored without problems.
 
It reads everything from ada0 and writes it back to the same device at the same place. That operation is very dangerous though to run on a live system
I never attempted anything like that but, perhaps, when booted single user (with proper backups at hand) maybe ...

P.S.: Also let us know if it survived the reentry :)
 
I'm curious what the results are here. I probably wouldn't use dd for this, I'd probably use ddrescue or similar.

But, that being said, this is a foolish thing to do. If you have any reason to believe that a HDD isn't behaving correctly, you should be immediately verifying that any backups you have are current and usable and then replacing the drive until and unless you can prove that it isn't failing.

HDDs are cheap these days and data recovery services are not. And that's assuming the service can even recover the data.
 
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