Thanks so much for all the help. Writing of script will be the best choice..
Thanks again to all of you....
________________________________
From: Peter Grandi <pg_...@el5.for.sabi.co.uk>
To: RH EL5 <rhelv5-list@redhat.com>
Sent: Wednesday, January 4, 2012 5:30 PM
Subject: Re: [rhelv5-list] Regarding sparse file
[ ... ]
>> Ok I completely agree what you said. So if I want to deallocate if any
>> zeros then what is the procedure?
> man cp
> In particular, the --sparse option
That (and other programs like 'rsync' or GNU 'tar' that support
sparse copying) is good if you can make a copy.
If you want to allocate logical blocks full of zeroes, you must
use a file system that implements so called "hole punching"
'ioctl's, and I can only remember (recent versions) of 'ext4',
OCFS2 and (even fairly old versions) of XFS that do.
There is a summary here: http://lwn.net/Articles/415889/
You must then write a program that scans the file and then
issues the "hole punching" 'ioctl's in the places you want, as I
think that there is no such ready-made program (but just checked
and there is one at least for XFS). But it is really simple to
write.
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