Re: [Xen-API] look into VHD VDI from Control Domain in XCP 1.6

[Joseph Hom <jhom@xxxxxxxxxxxxx>]

Sorry I mistyped the path. The device path listed in the vbd is what you should 
be using kpartx on

e.g.

kpartx -av 
/dev/sm/backend/55ea20d2-8611-1121-9e9e-c26b35ac1852/5e2c31a5-1d1b-4abe-9892-1fa3bc47b532

This will expose the partitions which you can find in /dev/mapper.

-----Original Message-----
From: George Shuklin [mailto:george.shuklin@xxxxxxxxx] 
Sent: Tuesday, January 08, 2013 12:35 PM
To: Joseph Hom
Cc: xen-api@xxxxxxxxxxxxx
Subject: Re: [Xen-API] look into VHD VDI from Control Domain in XCP 1.6

Yep, but what the uuid is that '55ea...'? I xee it nowhere in related
objects:

uuid ( RO)             : 9a4ee27b-d990-4887-ff49-e2c1fb100061
           vm-uuid ( RO): 53c3d878-b60b-48ec-aaac-73f7adf9ab3d
     vm-name-label ( RO): Control domain on host: test
          vdi-uuid ( RO): 5e2c31a5-1d1b-4abe-9892-1fa3bc47b532
             empty ( RO): false
            device ( RO): 
sm/backend/55ea20d2-8611-1121-9e9e-c26b35ac1852/5e2c31a5-1d1b-4abe-9892-1fa3bc47b532

.....

After some guessing: this is SR uuid.

xe vdi-list uuid=5e2c31a5-1d1b-4abe-9892-1fa3bc47b532
uuid ( RO)                : 5e2c31a5-1d1b-4abe-9892-1fa3bc47b532
           name-label ( RW): test1
     name-description ( RW):
              sr-uuid ( RO): 55ea20d2-8611-1121-9e9e-c26b35ac1852
         virtual-size ( RO): 2147483648
             sharable ( RO): false
            read-only ( RO): false



08.01.2013 22:29, Joseph Hom ÐÐÑÐÑ:
> That is due to the new sm backend that was introduced. When a vbd is 
> plugged into dom0 is no longer shows up as a straight block device 
> under /dev/
>
> The new version of xe-edit-bootloader addresses this and can be used as a 
> pointer on what to do.
>
> Hint: kpartx -av /dev/sm/backend/55ea20d2-8611-1121-9e9e-c26b35ac1852
> ls /dev/mapper/55ea20d2-8611-1121-9e9e-c26b35ac1852*
>
> -----Original Message-----
> From: xen-api-bounces@xxxxxxxxxxxxx 
> [mailto:xen-api-bounces@xxxxxxxxxxxxx] On Behalf Of George Shuklin
> Sent: Tuesday, January 08, 2013 12:08 PM
> To: xen-api@xxxxxxxxxxxxx
> Subject: Re: [Xen-API] look into VHD VDI from Control Domain in XCP 
> 1.6
>
> Ok, here important stuff. When VBD is plugged to dom0, it plugging not as 
> 'normal' device (with udev attention), but as device in /dev/sm/backend.
>
> Here sample log (change uuids on you taste):
>
> xe vbd-create vm-uuid=53c3d878-b60b-48ec-aaac-73f7adf9ab3d
> vdi-uuid=5e2c31a5-1d1b-4abe-9892-1fa3bc47b532 device=6 xe vbd-plug 
> uuid=407eb3a6-919f-f605-0883-e12aaa91321d
>
> ls -la /dev/sm/backend/55ea20d2-8611-1121-9e9e-c26b35ac1852/
> ÐÑÐÐÐ 4
> drwxr-xr-x 2 root root     80 ÐÐÐ  8 21:57 .
> drwxr-xr-x 3 root root     60 ÐÐÐ 18 17:40 ..
> brw------- 1 root root 253, 0 ÐÐÐ  8 21:57
> 5e2c31a5-1d1b-4abe-9892-1fa3bc47b532
> -rw-r--r-- 1 root root    852 ÐÐÐ  8 21:57
> 5e2c31a5-1d1b-4abe-9892-1fa3bc47b532.attach_info
>
> I have no idea why '55' uuid (and what it means), but
> 5e2c31a5-1d1b-4abe-9892-1fa3bc47b532 is block device after whole VHD tree 
> joining/parsing and so on.
>
> You can see actual path in xe vbd-list output (device field).
>
> 05.01.2013 11:33, Alexandre Kouznetsov ÐÐÑÐÑ:
>> Hello.
>>
>> El 04/01/13 23:14, George Shuklin escribiÃ:
>>> Use xe vbd-create between vdi and dom0 (which is normal VM mostly), 
>>> and xe vbd-plug.
>> Yes, that's what I have done following the example from Citrix forum.
>>
>> In case of a normal DomU:
>> I create VBD linking the VM with VDI, I issue vbd-plug, the block 
>> device becomes visible in dmesg under DomU.
>>
>> In case of Dom0:
>> I create VBD linking the VM (vm-list refers to it as "Control 
>> Domain", no mistake) with VDI, I issue vbd-plug, no sign of the new 
>> block device in dmesg or under /dev.
>>
>>> You can see some sample usage in 'xe-edit-bootloader' command 
>>> (somewhere in /opt/xensource/)
>> Hm. I believe I'm doing it just the same way as in the script, except 
>> by the "device=" directive for vbd-create, use specific string like 
>> "xvdn".
>> Should it make the difference? Can't test, I shot down my testing 
>> range before leaving the office.
>>
>> So, must I understand that the XCP's regular way of manipulating 
>> VDI's contents from within Dom0, is attaching the VDI to it via a VBD?
>> Looks like a good abstraction, except that it won't work that easily 
>> on a host without XCP infrastructure (for example, in some rescue 
>> scenario).
>>
>> Then, what vhdpartx is good for?
>>
>> Cheers.
>>
>>
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