[Users] oVirt Python SDK: getting the full filenames of disk images

Thu Dec 12 06:32:37 EST 2013

Dan, thank you for a nice advice.  I have forgotten about domxml rich opportunities…

Vitaly Isaev
Software engineer
Information security department
Fintech JSC, Moscow, Russia

From: Dan Yasny [mailto:dyasny at gmail.com]
Sent: Monday, December 09, 2013 8:14 PM
To: Исаев Виталий Анатольевич
Cc: users at ovirt.org
Subject: Re: [Users] oVirt Python SDK: getting the full filenames of disk images

Please see reply inline

On Mon, Dec 9, 2013 at 12:03 AM, Исаев Виталий Анатольевич <isaev at fintech.ru<mailto:isaev at fintech.ru>> wrote:
Hi Dan, glad to meet you both on LOR and in this mailing list :)

I know, I'm everywhere :)

Unfortunately ovirtsdk.infrastructure.brokers.<anything> classes instances miss information about the higher objects very often. The typical situation is returning of empty string when we ask something about the parent from the child object ("child" and "parent" in terms Red Hat Enterprise Virtualization objects hierarchy). Consider this Python code:

                from ovirtsdk.api import API

                from ovirtsdk.xml import params

                ...

                api = API(...)

                d = api.vms.list()[i].get_disks().list()[i]                                                 # ovirtsdk.infrastructure.brokers.VMDisk class instance, i – any number in range(api.vms.list().__len__())

                s = d.get_storage_domains().get_storage_domain()[0]              # ovirtsdk.infrastructure.params.StorageDomain class instance

                t = s.get_data_center()                                                                              # NoneType

So you can see that this approach does not work here.

I hope Michael or Itamar can shed some more light on this part, I don't have a system in front of me to check. AFAIR some objects aren't linked directly and you simply need to know how to get to them, I've had plenty of help from Michael before, when I was running a seemingly correct script, and getting no data, simply because I didn't understand the way the API looks for objects and relationships.

Our purpose is checking the VM’s disk image integrity (I mean integrity of system files, stored in /boot, /bin, /sbin, /lib etc.) every time the VM starts. The integrity checking script is written in Python and relies on libguestfs and vdsm hooks. Specific vdsm hook runs our script and block the VM’s boot process until the correctness of the system files hash sums will be checked. But libguestfs requires the full path to the disk to be handled, and it’s not integrated with ovirt infrastructure. And here we face with a task of full disk image filenames definition.

I assume you are using before_vm_start? This will catch the VM definitions, as passed by the engine, and allow you to reassemble the domxml. You can get the disk path from the domxml directly, bypassing the engine APIs completely.
The problem however, if you are doing this on block storage, is that the right LV will not be prepared for use by vdsm at this point, so you'll have to make it accessible manually, then disable access and let vdsm do it's job. Much easier with NFS/Gluster of course.

Thank you,
Vitaly Isaev
Software engineer
Information security department
Fintech JSC, Moscow, Russia

From: Dan Yasny [mailto:dyasny<mailto:dyasny>@gmail.com<http://gmail.com>]
Sent: Friday, December 06, 2013 8:56 PM
To: Исаев Виталий Анатольевич
Cc: users at ovirt.org<mailto:users at ovirt.org>
Subject: Re: [Users] oVirt Python SDK: getting the full filenames of disk images

Probably not, but you can
- get the disk image UUID (that's the name in the filesystem or LV name),
- get the UUID of the storage domain (that will be the top level dir name or VG name)
- get the DC UUID (this will be the top level dir name and the mount point for LVM)

Then compose the path out of these. Keep in mind that the disk UUID you get is the latest leaf in a snapshot tree, and if you need the entire chain of images, you need to recursively traverse the tree starting at the leaf, using the PUUID tag to find the parent.

Might be a better way, but I'm not aware of it.

Moreover, if you explain why you need to touch those images manually instead of letting ovirt handle everything, we might be able to suggest a better way

--
D

On Wed, Dec 4, 2013 at 2:34 AM, Исаев Виталий Анатольевич <isaev at fintech.ru<mailto:isaev at fintech.ru>> wrote:
Dear ovirt-engine users,

I will be appreciated if someone experienced in oVirt Python SDK could advice the method of getting the full filename of the VM’s disk images in the RHEV hypervisor’s file system. Can I get filename with a full file system path from a ovirtsdk.infrastructure.brokers.VMDisk class instance?

If Python SDK (what is preffered) can’t provide such an information, may be it is still possible with RHEV-M REST API?

Thank you,
Vitaly Isaev
Software engineer
Information security department
Fintech JSC, Moscow, Russia

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