Re: [Xen-users] Can not attach vhd image and start vhd-based domU

[Andrey <basketboy@xxxxx>]

15.05.2015 15:11, Ian Campbell ÐÐÑÐÑ:
> On Fri, 2015-05-15 at 14:03 +0300, Andrey wrote:
> > Hello,
> >
> >    I'm trying to block-attach vhd image to dom0 using blktap2 with xen
> > 4.4 standard package installed on Debian Jessie, but with no luck.
> >
> > 'xl -vvv block-attach 0 /home/data/centos-6.vhd,vhd,xvda,w'
> As you've observed this will use qdisk not blktap. I suspect your issue
> is lack of a qemu process running in dom0 to service the qdisk requests.
> See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770456 .
Great, will try to apply patch.

> If you want blktap2 for real then you will need to force the backend
> selection.
>
> I don't think that is possible with the deprecated syntax you are using.
> According to
> http://xenbits.xen.org/docs/4.4-testing/misc/xl-disk-configuration.txt
> something like:
>      
> format=vhd,vdev=xvda,access=w,backendtype=tap,target=/home/data/centos-6.vhd
> Should do the trick (nb, target= must be last).
>
> For debugging it can be useful to do "xl -N block-attach 0 <diskspec>",
> this is just a dry-run block attach to dom0, which will print the parsed
> version of the spec
Big thanks for the hints. Strange but I get the error while trying to 
run xl block-attach 0 
format=vhd,vdev=xvda,access=w,backendtype=tap,target=/home/data/centos-6.vhd 
:
libxl: error: libxl_device.c:289:libxl__device_disk_set_backend: no 
suitable backend for disk xvda
libxl: error: libxl.c:1727:device_addrm_aocomplete: unable to (null) device
libxl_device_disk_add failed.

xl -N produces correct parsing:

disk: {
    "backend_domid": 0,
    "backend_domname": null,
    "pdev_path": "/home/data/centos-6.vhd",
    "vdev": "xvda",
    "backend": "tap",
    "format": "vhd",
    "script": null,
    "removable": 0,
    "readwrite": 1,
    "is_cdrom": 0
}

> Ian.
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