[Users] mount ploop image from read-only fs

[Roman Haefeli]

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
> > 
> > 
> > 
> 
>