Debian Bug report logs - #288354
lvm2: Machine freezes on snapshot creation for root LV.

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Package: lvm2; Maintainer for lvm2 is Debian LVM Team <pkg-lvm-maintainers@lists.alioth.debian.org>; Source for lvm2 is src:lvm2.

Reported by: "Dr. Andreas Krüger" <andreas.krueger@dv-ratio.com>

Date: Mon, 3 Jan 2005 08:48:05 UTC

Severity: normal

Found in version 2.00.24-1

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Report forwarded to debian-bugs-dist@lists.debian.org, Patrick Caulfield <patrick@debian.org>:
Bug#288354; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to "Dr. Andreas Krüger" <andreas.krueger@dv-ratio.com>:
New Bug report received and forwarded. Copy sent to Patrick Caulfield <patrick@debian.org>. Full text and rfc822 format available.

Message #5 received at submit@bugs.debian.org (full text, mbox):

From: "Dr. Andreas Krüger" <andreas.krueger@dv-ratio.com>
To: submit@bugs.debian.org
Subject: lvm2: Machine freezes on snapshot creation for root LV.
Date: Mon, 03 Jan 2005 09:44:52 +0100
[Message part 1 (text/plain, inline)]
Package: lvm2
Version: 2.00.24-1
Severity: normal

My machine freezes up when I try to create a snapshot of the volumne
that contains the root file system.  In case it matters, that file system
also hosts both /etc and /var.

The details:

I used the following command:

   lvcreate -s -A n -v -l 20 --name rootfreeze /dev/mvg/root

From the screen, I copied (as in pen&paper) the following information:

  Setting chunksize to 16 sectors
  Finding volume group "mvg"
  Creating logical volumne rootfreeze
  Archiving volume group "mvg" metadata.
  Creating volume group backup "/etc/lvm/backup/mvg"
  Found volume group "mvg"
  Loading mvg-rootfreeze
  Zeroing start of logical volume "rootfreeze"
  Found volume group "mvg"
  Removing mvg-rootfreeze
  Found volume group "mvg"
  Found volume group "mvg"
  Found volume group "mvg"
  Loading mvg-rootfreeze-cow

At this point, the computer completely freezes.

With the exception of the Alt+Sysreq emergency break, which still worked. To 
some extend, at least: Sync seemed to work, switch mounts to read-only did NOT 
seem to work, reboot did.

After the reboot, oddly enough, the rootfreeze volumne was there as
requested!  (I have dm-setup in my initrd, see bug 271981).

Here is the output of "mount" reflecting the setup when I issued the
lvmcreate:

/dev/mapper/mvg-root on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
/dev/mapper/mvg-usr on /usr type ext3 (rw)
/dev/mapper/mvg-home on /home type ext3 (rw)
/dev/ide/host0/bus0/target0/lun0/part1 on /boot type ext2 (rw)
usbfs on /proc/bus/usb type usbfs (rw)
automount(pid1939) on /eulehome type autofs 
(rw,fd=4,pgrp=1939,minproto=2,maxproto=4)
automount(pid1974) on /bienehome type autofs 
(rw,fd=4,pgrp=1974,minproto=2,maxproto=4)
automount(pid2072) on /usb type autofs (rw,fd=4,pgrp=2072,minproto=2,maxproto=4)

Regards, and thank you for providing fine software.

Andreas

-- System Information:
Debian Release: 3.1
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)
Kernel: Linux 2.6.8-1-686
Locale: LANG=de_DE.UTF-8@euro, LC_CTYPE=de_DE.UTF-8@euro (charmap=UTF-8)

Versions of packages lvm2 depends on:
ii  libc6                       2.3.2.ds1-18 GNU C Library: Shared libraries an
ii  libdevmapper1.00            2:1.00.19-2  The Linux Kernel Device Mapper use
ii  lvm-common                  1.5.17       The Logical Volume Manager for Lin

-- debconf information:
  lvm2/snapshots:
[signature.asc (application/pgp-signature, attachment)]

Information forwarded to debian-bugs-dist@lists.debian.org:
Bug#288354; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Patrick Caulfield <patrick@debian.org>:
Extra info received and forwarded to list. Full text and rfc822 format available.

Message #10 received at 288354@bugs.debian.org (full text, mbox):

From: Patrick Caulfield <patrick@debian.org>
To: Dr. Andreas Krüger <andreas.krueger@dv-ratio.com>, 288354@bugs.debian.org
Subject: Re: Bug#288354: lvm2: Machine freezes on snapshot creation for root LV.
Date: Wed, 5 Jan 2005 13:58:51 +0000
On Mon, Jan 03, 2005 at 09:44:52AM +0100, "Dr. Andreas Krüger" wrote:
> Package: lvm2
> Version: 2.00.24-1
> Severity: normal
> 
> My machine freezes up when I try to create a snapshot of the volumne
> that contains the root file system.  In case it matters, that file system
> also hosts both /etc and /var.

Snapshots of the root filesystem are not currently supported in LVM2. There have
been a number of emails about this on the linux-lvm mailing list. I don't see a
quick resolution to the problem I'm afraid.


-- 

patrick



Information forwarded to debian-bugs-dist@lists.debian.org, Debian LVM Team <pkg-lvm-maintainers@lists.alioth.debian.org>:
Bug#288354; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Sam Morris <sam@robots.org.uk>:
Extra info received and forwarded to list. Copy sent to Debian LVM Team <pkg-lvm-maintainers@lists.alioth.debian.org>. Full text and rfc822 format available.

Message #15 received at 288354@bugs.debian.org (full text, mbox):

From: Sam Morris <sam@robots.org.uk>
To: 288354@bugs.debian.org
Subject: Workaround?
Date: Fri, 23 Jun 2006 13:59:46 +0100
May I suggest as a workaround, displaying an error message rather than
crashing the machine and scaring the crap out of the admin?

I just ran into this on a Sarge machine, except that I can't even boot
the system:

        device-mapper: 4.1.0-ioctl (2003-12-10) initialised: dm@uk.sistina.com
          Can't expand LV: Snapshot support missing from kernel?
          2 logical volume(s) in volume group "main" now active
        pivot_root: No sKernel panic: Attempted to kill init!
        uch file or dire ctory
        /sbin/init: 432: cannot open dev/console: No such file

-- 
Sam Morris
http://robots.org.uk/

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