[CentOS] Utility to zero unused blocks on disk

Tue Feb 9 04:01:36 UTC 2016
Robert Nichols <rnicholsNOSPAM at comcast.net>

On 02/08/2016 07:04 PM, Chris Adams wrote:
> Once upon a time, Greg Bailey <gbailey at lxpro.com> said:
>> Wes didn't say the reason he wanted to zero unused blocks, but I
>> always do this in kickstart scripts when constructing VM images as
>> the image size is considerably reduced by doing this...
> For that purpose, use something that can TRIM a VM image, like
> virt-sparsify.

That's doing the same thing.

virt-sparsify works by mounting the filesystem, filling it to capacity
with zeros, then performing a copy operation which skips over the
all-zero blocks, leaving them unallocated in the sparse destination

Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.