Fwd: [dm-devel] cow snapshot on cloop device

[Jacob Broido]

---------- Forwarded message ----------
From: Jacob Broido <jacob.broido at gmail.com>
Date: Aug 24, 2005 7:00 PM
Subject: Re: [dm-devel] cow snapshot on cloop device
To: Kevin Corry <kevcorry at us.ibm.com>

I am using dmsetup directly. and I do the following:
1) Create an empty file that will be used as cow backing storage
2) losetup the backing file to /dev/loop0
3) create a snapshot of main root_device on /dev/loop0
4) mount the cow snapshot


Here is the info you requested:
The kernel is a - 2.6.11.10 <http://2.6.11.10> + xen patch.
=======================================================
/ # dmsetup ls
root_master (253, 0)
root_cow0 (253, 1)
/ # dmsetup table
root_master: 0 4096128 linear 240:0 0 
root_cow0: 0 4096128 snapshot 253:0 7:0 P 8

/ # cat /proc/partitions

major minor #blocks name

7 0 loop0
8 0 sda
8 1 sda1
8 2 sda2
8 3 sda3
240 0 cloop0
252 0 dm-0
253 1 dm-1

/ # cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root.old / ext2 rw 0 0
/proc /proc proc rw,noadirtime 0 0
/sys /sys sysfs rw 0 0
/dev/hdc /cdrom iso9660 ro 0 0
/ramdisk /ramdisk tmpfs rw 0 0
/dev/mapper/root_cow0 /cow ext2 rw.noatime 0 0
====================================================

On 8/24/05, Kevin Corry <kevcorry at us.ibm.com> wrote: 
> 
> On Wed August 24 2005 11:35 am, Jacob Broido wrote:
> > Hi,
> > I am trying to set a cow snapshot on a cloop device. 
> > I managed to create a snapshot and mount it as read/write, but it 
> appears
> > that the data inside the /cloop appears invalid:
> >
> > Binary executables appear to be invalid, I perfomed diff between files 
> on 
> > snapshotted /dev/cloop, and the same files accessed directly through 
> cloop.
> >
> > The files were diffrent,
> > anyone has idea as to what can be the reason for this?
> 
> Are you using LVM, EVMS, or dmsetup to create your snapshot? Please send 
> in 
> the output from "dmsetup ls" and "dmsetup table", as well as the contents
> of /proc/partitions and /proc/mounts, after you have activated and mounted
> your snapshot.
> 
> --
> Kevin Corry
> kevcorry at us.ibm.com
> http://www.ibm.com/linux/
> http://evms.sourceforge.net/
> 



-- 
Not gonna be king of the world if you're slave to the grind
- Skid Row 


-- 
Not gonna be king of the world if you're slave to the grind
- Skid Row
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