S3ba’s Blog

To erase definitively all the data stored in an hard disk (floppy, pen drive, etc) the simple formatting is not enough, in fact is possible, with specified software, recover the "lost datas": this because the formatting or the process of deleting file don’t erase the file, but the link to hard disk sector where the effective file is stored, until this sector don’t be overwrite by another file.

Usually to way clean totally an hard drive is to write the drive with the pattern 0×00; in linux is possible to use the programm dd, an the command is:

# dd if=/dev/zero bs=4096 of=/dev/hdaX

 dd read in input the content of the device /dev/zero and write it in the destination device (/dev/hdax); the program read and write  4096 bytes at at time.