I'm playing with Master boot record. I decided to delete and restore it on my vmware machine.
With Ubuntu LiveCD I'm trying to erase partition entries and signature with command:
dd if=/dev/zero of=/dev/sda bs=1 skip=446 count=66
or:
dd if=/dev/urandom of=/dev/sda bs=1 skip=446 count=66
To verify my changes I check with command:
dd if=/dev/sda bs=1 skip=446 count=66 | hexdump -C
but I do not see zeros or random characters. Everything is unchanged.
I rebooted my machine. As expected I could not boot my os. Again I booted LiveCD and again I see no changes to MBR partitions and signature, old data are preserved. What is wrong?