1:55 p.m.
Hi-
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?
$ guestfish
Welcome to guestfish, the libguestfs filesystem interactive shell for
editing virtual machine filesystems.
Type: 'help' for a list of commands
'man' to read the manual
'quit' to quit the shell
<fs> add disk.img
<fs> run
<fs> list-filesystems
/dev/sda1: ext4
/dev/vg_guest/lv_root: ext4
/dev/vg_guest/lv_swap: swap
<fs> zerofree /dev/vg_guest/lv_root
Thanks for any light you can shed on this.
-Ben
3:38 p.m.
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
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://et.redhat.com/~rjones/virt-top
3:40 p.m.
On Thu, Sep 01, 2011 at 09:38:36PM +0100, Richard W.M. Jones wrote:
It might be advisable to keep a backup and check your filesystem
before and after with 'virt-ls --checksum'.
eg doing this:
http://libguestfs.org/virt-ls.1.html#differences_in_snapshots_and_backing...
but also adding the --checksum parameter to both commands.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine. Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/
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Ben Clay -
Richard W.M. Jones