Disk Duplication

ddis a command for low-level copying. As the disks on *nix platform are represented like normal files, so dd can take input from/output to these devices. We can also use dd to create a virtual disk.

To begin with, let 's try the following command:

sudo dd if=FILE of=FILE bs=BYTES count=BLOCKS

ddtakes few arguments:

• if

  : Input file FILE (e.g., /dev/zero,/dev/urandom)

• of

  : Output file FILE

• bs

  : Block size: read and write BYTES bytes at a time.

• count

  : copy only BLOCKS input blocks.

Example

Now we wish to create a file with zeros about 64MB

$ dd if=/dev/zero of=test.disk bs=64M count=1

After that, you can see the result showing:

PLEASE BE CAREFUL – dd is often nicknamed disk destroyer because it will happily overwrite any data you tell it to, including the stuff you wanted to keep if you make a mistake typing the command!