BIO_DELETE equivalent for file on FFS filesystem

[Chris Rees]

On Jun 14, 2012 5:49 AM, "Wojciech Puchar" <wojtek at wojtek.tensor.gdynia.pl>
wrote:
>>>
>>> file to take 900MB or... can i call some system function to "punch"
>>> holes?
>>
>>
>> I think you can only truncate the file at this time, pretty much like
>> brk() works for memory.
>
>
>
> BAD. suppose i keep windoze VM image on filesystem which takes 10GB but
uses 5GB.
>
> i could write simple program to find out what blocks are unused and
then...do nothing.
>

What if you cp it?

Chris