dd if=/dev/zero of=zero; rm -f zero

I saw this on macles site and its used to fill empty drive space with zeros to enhance compression speed. Is there a way to reverse it and "unzero". I lost a gig before i twigged on (could have been worse) I dont really want to have to recover to get the space back.
Thnx in advance

 

This is not supposed to anyhow hose your filesystem. How did you "lose a gig", just to understand you correctly?

 

had 5.6gig before the command and 4.4 when i killed it a few mins later...

 

The commandline is actually executing 2 commands. First it is zeroing the deleted files by writing them to a file called "zero", then it is deleting the file "zero". If you killed the thing before it had a chance to remove "zero", that would account for the lost space. Just delete the file "zero", by running the second part of the command:

rm -f zero

Cheers.

 

Sorted!
The file was listed as 0 kb which meant i almost overlooked it, and i had to reboot but it came back. Ta very much