mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2025-02-02 09:55:18 +00:00
cb7297c150
When playing with disk migration lately, I've noticed this warning in
domain logs:
WARNING: Image format was not specified for 'nbd://masina:49153/drive-virtio-disk0' and probing guessed raw.
Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
Specify the 'raw' format explicitly to remove the restrictions.
So I started digging into qemu source code to see what has triggered
the warning. I'd expect qemu to know formats of guest's disks since we
tell them on command line. This lead me to qmp_drive_mirror() where
the following can be found:
if (!has_format) {
format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
}
So, format is automatically initialized from the disk iff mode !=
"existing". Unfortunately, in migration we are tied to use this mode
(NBD doesn't support creating new images). Therefore the only way to
avoid this warning is to pass format. The discussion on the mail-list [1]
resulted in the code that always forces NBD export as "raw" format.
[1] https://www.redhat.com/archives/libvir-list/2015-June/msg00153.html
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Pavel Boldin <pboldin@mirantis.com>
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>