I just made a huge mistake with dd while trying to copy the data from a DVD archive to my hard drive. (I was getting read errors using cp, so I wanted to see if 'dd' would work.) Anyway, I did "sudo dd if=/dev/hdd of=/dev/hda9", and now I think I may have wiped out my hda9 partition.

'df' before my screw-up showed hda9 as:
'df' now shows:
which I don't understand. (What does the 16T mean?) The DVD I was attempting to copy from was 4.4GB, and the hda9 partition was 22GB. Has the entire partition been overwritten? 'df' is saying that usage is 100%, but there doesn't appear to be anything there at all. ('ls' returns nothing.) BTW, dd completed with:

Could someone please help me understand what I've done, and if there's anyway to undo it? Thanks in advance...

Yes, you did. Tee hee. Ahem.

The T stands for Terabytes (1024 Gigabytes). Since it's unlikely your partition is that big, it basically means your filesystem is screwed.

Unless you have a backup, there isn't much you can do except kiss goodbye to your data and remake the filesystem. Don't feel too bad, most of us have done something like this, it's a good learning experience. Well, it's a learning experience, I don't know about "good".

In future, you should copy the data to a file/directory, not to a raw partition.

I was afraid of that. Most of the data was backed up, but some was not. :-(

So I should just go ahead and re-format the partition? No chance of making nice again? (Also, I failed to mention in my query, the filesystem is ext3.)

Thanks for the reply...

Yeah, just remake the filesystem. When you write to a raw partition, the fs is toast, so that's about all you can do
(unless of course, you're restoring a previous backup of the exact same partition).

I've toasted a few filesystems myself (not to mention hard drives ), I've found that it's a good idea to re-read every root/su/sudo command (that is going to delete/overwrite something) several times before pressing return.

should of been dd if=/dev/dvd of=dvdimage.iso