[Users] mount ploop image from read-only fs

[Roman Haefeli]

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. Also the alleged 'old' ploop is 1.6. The
difference is that I can't use ploop_userspace for images that have been
created using ploop from a debian package I created myself based on the
rpm packages. ploop_userspace seems to work fine with ploop images that
have been created using ploop from the official openvz Debian
repository. 

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
> > >> >
> > >> >
> > >> >
> > >>
> > >>
> > >
> > >
> > > _______________________________________________
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> > 
> > 
> > 
> 
>