[Libguestfs] guestfish zerofree on LVM ?

[Richard W.M. Jones]

On Thu, Sep 01, 2011 at 02:55:06PM -0400, Ben Clay wrote:
> Is it safe to use the zerofree utility on an ext4 partition inside
> an LVM with guestfish?  I know zerofree works on ext4, but I am
> unsure about LVM.  The info page uses the syntax "zerofree
> <device>", so using the info page example, could I (safely) do
> something like the following?

Using it on logical volumes makes no difference, it'll just work the
same way as on partitions or whole devices.

HOWEVER, I would be cautious about using zerofree at all.  It's been
checked reasonably carefully against ext2/ext3, but I don't think
anyone has looked at whether it does reasonable things on ext4
(particularly w.r.t. filesystems with extents).

So it might work, or it might silently corrupt files ...  It might be
advisable to keep a backup and check your filesystem before and after
with 'virt-ls --checksum'.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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