[Users] mount ploop image from read-only fs

Pavel Odintsov pavel.odintsov at gmail.com
Mon Sep 15 03:49:08 PDT 2014 

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 :)

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
>> > > >
>> > > >
>> > > >
>> > >
>> > >
>> >
>> >
>>
>>
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>
>
>
> --
> Sincerely yours, Pavel Odintsov



-- 
Sincerely yours, Pavel Odintsov

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