Re: [Qemu-devel] -snapshot

[Stefan Hajnoczi]

On Thu, Dec 16, 2010 at 4:34 PM, Amador Pahim <address@hidden> wrote:
> Thank you for your answer. Just one more question: If, while my
> "snapshot" vms are running, the main disk is modified by a non
> "snapshot" vm? For example, installing some extra software.. this can
> freeze vms or something?

Correct, it is not safe to modify the base image while there is
another disk image backed off it.

The reason for this is that the image only needs to store the changes
that were made on top of the base image.  For anything which hasn't
been modified it will go back to the base image and read data from
there.

If you modify the base image, then the filesystem in the base image is
not longer what your image file was created from and you have an
inconsistent view of the disk.  It leads to odd behavior and is
unsafe.

Stefan