Xen users - Feb 2007 - HELP PLEASE !! How to Recover deleted img file?

Hy today I accidentaly delete the img file of one of my domU. The guest is
still up and running. How can i recover the img file from which it was
loaded?
I tried lsof but i don''t see any open file by xen regarding my domU

Thanks!

-- 
Radu Stanescu


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On 2/2/07, Radu Stanescu <radukn@gmail.com> wrote:
> Hy today I accidentaly delete the img file of one of my domU. The guest is
> still up and running.
Interesting, can you even login, and the system still works?
Then Xen is saving the file from being deleted totally until the vm is
shut down. After that, it will probably free the open file, and it
will be gone.

So don''t stop the vm, and do a full rsync backup ASAP.
>How can i recover the img file from which it was
> loaded?
> I tried lsof but i don''t see any open file by xen regarding my
domU
This is a generic linux problem and has nothing to do with Xen.

I think, if you once stop the vm and have not done an rsaync backup as
said above, you have  not much chances, but at very first, you should
stop the machine completely and not use the harddisk where the lost
image resided.

Go to linux recovery mailing lists and read about that.

As far as I know, when you don''t use special techniques in advance,
(there is some libraray that makes rm not really delete stuff, AFAIK,
and for sure we all have backups, at least _after_ we lost important
data the first time, right?!), it''s absolitely not easy to recover
lost files.

Heninng

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On Fri, Feb 02, 2007 at 02:15:30PM +0100, Henning Sprang
wrote:
> On 2/2/07, Radu Stanescu <radukn@gmail.com> wrote:
> >Hy today I accidentaly delete the img file of one of my domU. The guest
is
> >still up and running.
> 
> Interesting, can you even login, and the system still works?
> Then Xen is saving the file from being deleted totally until the vm is
> shut down. After that, it will probably free the open file, and it
> will be gone.
> 
> So don''t stop the vm, and do a full rsync backup ASAP.
> 
 Not xen. It is a property of the unix kernel. It won''t delete the file
unless the open file descriptor count is 0. Maybe if you ask in the linux kernel
mailing list, someone might be able to help you out.

 Thanks.



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> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com 
> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of 
> Henning Sprang
> Sent: 02 February 2007 13:16
> To: Radu Stanescu
> Cc: xen-users@lists.xensource.com
> Subject: Re: [Xen-users] HELP PLEASE !! How to Recover 
> deleted img file?
> 
> On 2/2/07, Radu Stanescu <radukn@gmail.com> wrote:
> > Hy today I accidentaly delete the img file of one of my 
> domU. The guest is
> > still up and running.
> 
> Interesting, can you even login, and the system still works?
> Then Xen is saving the file from being deleted totally until the vm is
> shut down. After that, it will probably free the open file, and it
> will be gone.
> 
> So don''t stop the vm, and do a full rsync backup ASAP.
That seems like good solution to me. 

You could even attach another disk-device and copy to that (xm
block-attach DomID BackDev FrontDev Mode [BackDomain] is the command to
use). Of course, you can''t save things that aren''t files, but
at least
if you have some important data on file(s) in the domain, you can save
those. Anything else should be salvagable by re-installing the OS +
apps. 
> 
> >How can i recover the img file from which it was
> > loaded?
> > I tried lsof but i don''t see any open file by xen regarding
my domU
> 
> This is a generic linux problem and has nothing to do with Xen.
Yes. Linux (like all Unix versions) will keep the file alive but
invisible until the last user of the file closes it. Since it''s an
image
file, there''s most likely only one user of the file, and
that''s the VM
itself (or more precisely, the  part of Dom0 that manages your
image-file to disk translation for the DomU). 
> 
> I think, if you once stop the vm and have not done an rsaync backup as
> said above, you have  not much chances, but at very first, you should
> stop the machine completely and not use the harddisk where the lost
> image resided.
> 
> Go to linux recovery mailing lists and read about that.
> 
> As far as I know, when you don''t use special techniques in
advance,
> (there is some libraray that makes rm not really delete stuff, AFAIK,
> and for sure we all have backups, at least _after_ we lost important
> data the first time, right?!), it''s absolitely not easy to recover
> lost files.
Indeed. It used to be very easy in the old days with DOS (as long as new
data wasn''t added to the disk), but modern file-systems aren''t
quite so
trivially designed, and to modify the right places to recover files
within the filesystem gets very hairy very quickly. Best way is to save
what you can from inside the VM, and recreate what you can''t save -
you''ll waste much more time trying to recover the file itself, for no
real value. 

--
Mats
> 
> Heninng
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
> 
> 
> 


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Hewh!

I did it! I recovered my img file! :D  Ext3 doesn''t permite undelete,
but
hopefully xen mount img file as loop devices so doing a "losetup -a"
will
show xen mounted devices then with dd you can recover from the /dev/loopXX
to a img file. It is recommended to stop on the domU all daemons that could
write anything to the hdd while doing the dd. after recovery, fsck the
recovered file and recreate the vm from the recovered file.

Thank you very much for you help guys!



On 2/2/07, Radu Stanescu <radukn@gmail.com> wrote:
>
> Hy today I accidentaly delete the img file of one of my domU. The guest is
> still up and running. How can i recover the img file from which it was
> loaded?
> I tried lsof but i don''t see any open file by xen regarding my
domU
>
> Thanks!
>
> --
> Radu Stanescu
>
>

-- 
Radu Stanescu
Best Internet Security Systems
www.biss.ro
radukn@gmail.com
radukn@biss.ro
0722.234.788


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Henning Sprang wrote:
> On 2/2/07, Radu Stanescu <radukn@gmail.com> wrote:
>> Hy today I accidentaly delete the img file of one of my domU. The 
>> guest is
>> still up and running.
>
> Interesting, can you even login, and the system still works?
> Then Xen is saving the file from being deleted totally until the vm is
> shut down. After that, it will probably free the open file, and it
> will be gone.
>
> So don''t stop the vm, and do a full rsync backup ASAP.
>
>> How can i recover the img file from which it was
>> loaded?
>> I tried lsof but i don''t see any open file by xen regarding my
domU
>
> This is a generic linux problem and has nothing to do with Xen.
>
> I think, if you once stop the vm and have not done an rsaync backup as
> said above, you have  not much chances, but at very first, you should
> stop the machine completely and not use the harddisk where the lost
> image resided.
>
> Go to linux recovery mailing lists and read about that.
>
> As far as I know, when you don''t use special techniques in
advance,
> (there is some libraray that makes rm not really delete stuff, AFAIK,
> and for sure we all have backups, at least _after_ we lost important
> data the first time, right?!), it''s absolitely not easy to recover
> lost files.
>
> Heninng
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>
>
>
This site may be of some help.

http://e2undel.sourceforge.net/recovery-howto.html


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On 2 Feb 2007 at 14:46, Radu Stanescu wrote:
> Hy today I accidentaly delete the img file of one of my domU. The guest is
> still up and running. How can i recover the img file from which it was
> loaded?
> I tried lsof but i don''t see any open file by xen regarding my
domU
UNIX semantics mean that the file will go away once it''s no longer
open. Can you
do something like (please refine!) in DomU?:

tar cf - / | rsh server_with_lots_of_space "cat >backup.tar"

You could also try a blockwise dd of the partitions, but I would not recommend
it.

Ulrich


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On Fri, 2007-02-02 at 14:46 +0200, Radu Stanescu wrote:
> Hy today I accidentaly delete the img file of one of my domU. The
> guest is still up and running. How can i recover the img file from
> which it was loaded? 
> I tried lsof but i don''t see any open file by xen regarding my
domU
> 
> Thanks!
> 
> -- 
> Radu Stanescu
> 
If anything, Xen has more or less acted like a safety net. The file you
deleted isn''t deleted (yet) because something is still accessing (lock
!
= 0) it.

What I would do is create a second loop device large enough to hold your
data, xm block-attach it after formatting it mount it and back up any
way you see fit. Remember, don''t include the backup drive itself in the
copy / rsync / tar (whatever, you get the picture).

A slower method would be just fire up rsync (use ssh if weary of trying
to install rsyncd on the phantom system).

Grab as if you would in a burning building, and whatever you do , don''t
stop the VM :)

Hope this helps, 
--Tim
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> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users

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