Re: KVM can't use Blockdevice anymore

[Santiago Vila <sanvila@debian.org>]

El 8/2/25 a las 19:10, basti escribió:
> Now KVM cant use block devices anymore.

Hi. I found a similar problem very recently.

I tried to use a virtual machine which I defined a long time ago,
but did not use for a long time (probably several years, during which
the host was upgraded to Debian 12 in the meantime)

What I did was to undefine the machine (which removes its xml
snippet at /etc/libvirt/qemu) and install it again with
virt-manager, using the same LVM logical volume as the disk.

After that, it worked again, and I also noticed the small change
in the xml file.

I had this:

-    <emulator>/usr/bin/kvm</emulator>
-    <disk type='file' device='disk'>
-      <driver name='qemu' type='raw'/>
-      <source file='/dev/k/mymachine'/>

and now I have this:

+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw' cache='none' io='native' discard='unmap'/>
+      <source dev='/dev/k/mymachine'/>

In the above, "k" is the name of my LVM group, so the disk was really a device,
not a file, and maybe that's why it did not want to work with the old configuration.

Hope this helps.

Thanks.