Re: Useful use of dd

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Teemu Likonen wrote:
> For this new subject I will add another use: quickly create empty file
> of specific size, for example 5 * 1024 bytes:
>    $ dd of=empty obs=1024 seek=5 count=0

Not to forget creation of sparse files with few disk consumption.

For testing zisofs i have this in a script:

  #!/bin/bash
  # 100gb with big holes
  for i in {1..100}
  do
    echo $i | dd of=100gb bs=1 seek="$i"G 2>/dev/null
  done

The resulting file "100gb" occupies 404 KB in an ext4 filesystem.
(It shall not contain entirely zeros. So it is not the smallest possible
100 GiB file.)


Have a nice day :)

Thomas