[Openstack-operators] Reducing ext4/qcow2 snapshot size

Lorin Hochstein lorin at nimbisservices.com
Tue Aug 21 01:04:02 UTC 2012

On Aug 20, 2012, at 12:47 PM, Samuel Winchenbach <swinchen at gmail.com> wrote:

> Hi all,
> I launched a large (100 GB) VM and made the changes I wanted
> (installed software, created users, etc...)  and made a snapshot.
> Now I would like to launch VMs from that snapshot with a smaller disk
> size, but no mater what flavor I select it always creates a 100GB
> image.
> Is there a way to reduce the ext4 partition size inside the qcow2 disk
> image?   It might involve creating a new image file and cloning over
> the original image?  If so what tools do you use for the cloning?

You can mount the qcow2 image in your file system using qemu-nbd (see http://en.wikibooks.org/wiki/QEMU/Images#Mounting_an_image_on_the_host) and then resize the partition using the e2fsprogs tools (e.g., see http://en.positon.org/post/Resize-an-ext3-ext4-partition).

I believe you can also use libguestfs <http://libguestfs.org/> as an alternative to qemu-nbd, but I've never tried it.

Take care,

Lorin Hochstein
Lead Architect - Cloud Services
Nimbis Services, Inc.

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