Libguestfs - Jul 2016 - Re: Changing a given image from virtio-blk to virtio-scsi

Any idea what 'virt-customize' script I should use to convert from
virtio-blk (vda, vdb...) to virtio-scsi (sda, sdb...) ?

I've tried naively to convince libvirt to use virtio-scsi and still present
it to the guest as 'vd*' - that didn't work (


<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source
file='/dev/shm/run/default/images/lago_basic_suite_master_storage_root.qcow2'/>
      <backingStore type='file' index='1'>
        <format type='raw'/>
        <source file='/home/lagostore/phx_repo:el7-base:latest'/>
        <backingStore/>
      </backingStore>
     * <target dev='vda' bus='scsi'/>*
      <boot order='1'/>
      <alias name='scsi0-0-0'/>
      <address type='drive' controller='0' bus='0'
target='0' unit='0'/>
    </disk>


TIA,
Y.

On Thu, Jul 14, 2016 at 06:54:20PM +0300, Yaniv Kaul
wrote:
> Any idea what 'virt-customize' script I should use to convert from
> virtio-blk (vda, vdb...) to virtio-scsi (sda, sdb...) ?
You'll find that you have to recreate the initrd, else it won't boot
(I'm assuming this is a Linux guest).

This is somewhat complicated and involves running some commands from
the guest.  Here's what virt-v2v does, although virt-v2v is especially
complicated because it supports doing this for everything back to RHEL 3(!)
You probably only need to run dracut if you only care about modern
Fedora & RHEL.

 
https://github.com/libguestfs/libguestfs/blob/master/v2v/convert_linux.ml#L794-L921
> I've tried naively to convince libvirt to use virtio-scsi and still
present
> it to the guest as 'vd*' - that didn't work (
Yeah the target dev names in libvirt XML aren't really arbitrary
strings.  Device names are controlled by the *guest* kernel, nothing
to do with the host which just exports one or another PCI device.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top

On Thu, Jul 14, 2016 at 9:03 PM, Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Thu, Jul 14, 2016 at 06:54:20PM +0300, Yaniv Kaul wrote:
> > Any idea what 'virt-customize' script I should use to convert
from
> > virtio-blk (vda, vdb...) to virtio-scsi (sda, sdb...) ?
>
> You'll find that you have to recreate the initrd, else it won't
boot
> (I'm assuming this is a Linux guest).
>
> This is somewhat complicated and involves running some commands from
> the guest.  Here's what virt-v2v does, although virt-v2v is especially
> complicated because it supports doing this for everything back to RHEL 3(!)
> You probably only need to run dracut if you only care about modern
> Fedora & RHEL.
>
>
>
https://github.com/libguestfs/libguestfs/blob/master/v2v/convert_linux.ml#L794-L921
>
> > I've tried naively to convince libvirt to use virtio-scsi and
still
> present
> > it to the guest as 'vd*' - that didn't work (
>
> Yeah the target dev names in libvirt XML aren't really arbitrary
> strings.  Device names are controlled by the *guest* kernel, nothing
> to do with the host which just exports one or another PCI device.
>
> Rich.
>
Does it make more sense to just use virt-builder and build it from scratch?
I did not find where in virt-builder I can actually specify virtio-scsi as
the type.
(BTW, the reason for all this is mainly to get 'discard' support...)
Y.

> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-top is 'top' for virtual machines.  Tiny program with many
> powerful monitoring features, net stats, disk stats, logging, etc.
> http://people.redhat.com/~rjones/virt-top
>