Re: How to restore my disk

[lee]

On Sun, Oct 03, 2010 at 10:40:11AM +0800, Dennis Cao wrote:
> Yesterday, I used this command to correct my MBR on my working computer,
>     $ dd if=/somefile of=/dev/sda  bs=512 count=1
> But very unfortunately, I used a wrong file. Now when I boot my
> working computer, it says:
>    Non-system disk or disk error
>    replace and strike any key when ready
> 
> I think the partition table is destroyed. How can I restore my disk?

You have overwritten the first 512 bytes (i. e. the first sector of
the disk, if the disk uses sectors that have 512 bytes). That
shouldn't have affected the partition table or other data on the
disk. Partition tables and data usually don't reside in the first 512
bytes of a disk.

The message you're getting allows to conclude that what you have
overwritten was something that allowed booting the computer from
/dev/sda. If you can restore whatever it was, you should be able to
boot as before.

You can boot a rescue system from a removable media or another disk
and take a look at /dev/sda. You'll very likely find your data is all
still there and unharmed.

As to how to restore your disk, it depends on what you consider as
"restore": To just retrieve the data, boot from a removable media and
make a backup. How to make it bootable again depends on what was used
for booting. If you have the right file you wanted to write with dd,
you could just write it ...