[Users] mount ploop image from read-only fs

Kir Kolyshkin kir at openvz.org
Fri Oct 24 15:46:39 PDT 2014


Roman,

Sorry for hijacking the thread, but back to the original problem.
Can you tell why vzctl snapshot-mount (or ploop snapshot-mount)
is/was not working for you? Ideally, please provide a detailed scenario.

Kir.


On 10/24/2014 05:25 AM, Roman Haefeli wrote:
> On Mon, 2014-09-15 at 14:49 +0400, Pavel Odintsov wrote:
>> Hello!
>>
>> I found bug! Thx Maxim Patlasov for helping with ploop v1 BAT format.
>>
>> Please check version from git and it support ploop v1 and v2 correctly :)
> It seems, it's not yet working properly for me. I can mount the ploop
> image, I can mount its filesystem, I can browse the folder structure and
> everything seems fine, but when I try to read any text file from etc/ or
> var/log/ I only see garbage or content that certainly belongs to a
> different file. Something with alignment seems still not correct.
>
> Please tell me how I can give you more useful information.
>
> Roman
>
>
>   
>
>> On Sun, Sep 14, 2014 at 2:15 AM, Pavel Odintsov
>> <pavel.odintsov at gmail.com> wrote:
>>> Thank you for report, its very useful for investigation. But only one
>>> difference between v1 and v2 is ploop disk size in header (32 vs 64 bit).
>>> But I use 64 bit numbers anywhere and everything should work fine. But I
>>> suppose alignment issues which not handled in my tool.
>>>
>>>
>>> On Friday, September 12, 2014, Roman Haefeli <reduzent at gmail.com> wrote:
>>>> On Fri, 2014-09-12 at 11:15 +0200, Roman Haefeli wrote:
>>>>> On Fri, 2014-09-12 at 10:56 +0200, Roman Haefeli wrote:
>>>>>> Hi Pavel
>>>>>>
>>>>>> I might have some more information on the issue. It seems that only
>>>>>> 'old' ploop images cannot be mounted by ploop_userspace. I actually
>>>>>> don't quite know the ploop version I used for creating the 'old' ploop
>>>>>> images,  but I know it works well with images created with ploop v1.6.
>>>>>>
>>>>>> Does ploop_userspace know about older image formats?
>>>>> No, it's also not the version.
>>>> Yes, there are different versions... I must have checked on the wrong
>>>> machine. ploop_userspace works well with images created by ploop v1.11,
>>>> but not with images created by ploop v1.6.
>>>>
>>>> Sorry for the noise.
>>>>
>>>> Roman
>>>>
>>>>
>>>>
>>>>>> On Thu, 2014-08-28 at 22:53 +0400, Pavel Odintsov wrote:
>>>>>>> Hello!
>>>>>>>
>>>>>>> No, it's not depend on kernel version. I created issue for you and
>>>>>>> will try to investigate:
>>>>>>> https://github.com/FastVPSEestiOu/ploop_userspace/issues/10 please
>>>>>>> track this github issue.
>>>>>>>
>>>>>>> On Thu, Aug 28, 2014 at 6:12 PM, Roman Haefeli <reduzent at gmail.com>
>>>>>>> wrote:
>>>>>>>> Some more info:
>>>>>>>>
>>>>>>>> It works on our test cluster where we have
>>>>>>>> 2.6.32-openvz-042stab093.4-amd64 installed. The report from below
>>>>>>>> is
>>>>>>>> from a host node running 2.6.32-042stab081.3-amd64.
>>>>>>>>
>>>>>>>> Is ploop_userspace dependent on kernel version?
>>>>>>>>
>>>>>>>> Roman
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, 2014-08-28 at 15:59 +0200, Roman Haefeli wrote:
>>>>>>>>> Hi Pavel
>>>>>>>>>
>>>>>>>>> Your tool comes in handy. That is exactly what we'd need.
>>>>>>>>> However, I had
>>>>>>>>> troubles using it. I did:
>>>>>>>>>
>>>>>>>>> $ ploop_userspace
>>>>>>>>> /virtual/.snapshot/nightly.0/vz/private/2006/root.hdd/root.hdd
>>>>>>>>>
>>>>>>>>>    We process:
>>>>>>>>> /virtual/.snapshot/nightly.0/vz/private/2006/root.hdd/root.hdd
>>>>>>>>>    Ploop file size is: 4193255424
>>>>>>>>>    version: 1 disk type: 2 heads count: 16 cylinder count: 81920
>>>>>>>>> sector count: 2048 size in tracks: 20480 size in sectors: 41943040 disk in
>>>>>>>>> use: 1953459801 first block offset: 2048 flags: 0
>>>>>>>>>    For storing 21474836480 bytes on disk we need 20480 ploop
>>>>>>>>> blocks
>>>>>>>>>    We have 1 BAT blocks
>>>>>>>>>    We have 262128 slots in 1 map
>>>>>>>>>    Number of non zero blocks in map: 3998
>>>>>>>>>    Please be careful because this disk used now! If you need
>>>>>>>>> consistent backup please stop VE
>>>>>>>>>    !!!ERROR!!! We can't found GPT table on this disk
>>>>>>>>>    !!!ERROR!!! We can't find ext4 signature
>>>>>>>>>    Set device /dev/nbd0 as read only
>>>>>>>>>    Try to found partitions on ploop device
>>>>>>>>>    First ploop partition was not detected properly, please call
>>>>>>>>> partx/partprobe manually
>>>>>>>>>    You could mount ploop filesystem with command: mount -r -o
>>>>>>>>> noload /dev/nbd0p1 /mnt
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Despite the errors, I tried to mount the ploop-partition:
>>>>>>>>>
>>>>>>>>> $ mount -r  -o noload /dev/nbd0p1 /mnt/
>>>>>>>>>
>>>>>>>>> and got:
>>>>>>>>>
>>>>>>>>>    mount: special device /dev/nbd0p1 does not exist
>>>>>>>>>
>>>>>>>>> Apparently, ploop_userspace wasn't able to read the GPT partition
>>>>>>>>> table.
>>>>>>>>>
>>>>>>>>> Tell me, if you need further information.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Roman
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Tue, 2014-08-19 at 12:48 +0400, Pavel Odintsov wrote:
>>>>>>>>>> Hello!
>>>>>>>>>>
>>>>>>>>>> You can mount ploop from RO root.hdd images with my tool:
>>>>>>>>>> https://github.com/FastVPSEestiOu/ploop_userspace but it's not
>>>>>>>>>> stable
>>>>>>>>>> now. You can try it and provide feedback.
>>>>>>>>>>
>>>>>>>>>> On Tue, Aug 19, 2014 at 12:24 PM, Roman Haefeli
>>>>>>>>>> <reduzent at gmail.com> wrote:
>>>>>>>>>>> Hi all
>>>>>>>>>>>
>>>>>>>>>>> At the university I work, we plan to switch all containers
>>>>>>>>>>> from simfs to
>>>>>>>>>>> ploop images on the long run. Despite the many advantages of
>>>>>>>>>>> using
>>>>>>>>>>> ploop, there is one major drawback that keeps us from
>>>>>>>>>>> switching
>>>>>>>>>>> production already now: We can't mount ploop images from
>>>>>>>>>>> read-only
>>>>>>>>>>> snapshots. In case of a recovery of a single file, we have to
>>>>>>>>>>> copy the
>>>>>>>>>>> ploop image from the read-only snapshot to some read-write
>>>>>>>>>>> storage in
>>>>>>>>>>> order to be able to mount it and extract the file. For CTs
>>>>>>>>>>> with huge
>>>>>>>>>>> ploop-images this is a big hurdle.
>>>>>>>>>>>
>>>>>>>>>>> Wouldn't it be possible to add a some flag to the 'ploop'
>>>>>>>>>>> utility to
>>>>>>>>>>> allow mounting ploop images from read-only storage (by
>>>>>>>>>>> bypassing some
>>>>>>>>>>> checks or skipping to set the dirty flag or whatever is
>>>>>>>>>>> necessary)?
>>>>>>>>>>>
>>>>>>>>>>> Cheers,
>>>>>>>>>>> Roman
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> Users mailing list
>>>>>>>>>>> Users at openvz.org
>>>>>>>>>>> https://lists.openvz.org/mailman/listinfo/users
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> Users mailing list
>>>>>>>> Users at openvz.org
>>>>>>>> https://lists.openvz.org/mailman/listinfo/users
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> Users mailing list
>>>> Users at openvz.org
>>>> https://lists.openvz.org/mailman/listinfo/users
>>>
>>>
>>> --
>>> Sincerely yours, Pavel Odintsov
>>
>>
>
> _______________________________________________
> Users mailing list
> Users at openvz.org
> https://lists.openvz.org/mailman/listinfo/users



More information about the Users mailing list