[Qemu-devel] [Bug 1354167] Re: On VM restart: Could not open 'poppy.qcow2': Could not read snapshots: File too large

[Kevin Wolf]

I just had the chance to help debugging another case of this, and it
turned out that qemu-img snapshot was used on the image while the VM is
running. This was likely the root cause of the corruption. So if you're
reading this, it's probably already too late, but I want to spell it out
anyway:

WARNING: Never open the same disk image from two processes at the same
time, except if both are read-only! If your VM is running, use the qemu
monitor of that VM (or libvirt functionality, which will do the same
internally) to do operations on the image. Use qemu-img only for images
of shut down VMs.


If you reported in this bug that you are affected, can you please reply and 
specify whether you ever used qemu-img (except for read-only subcommands) on 
your image while the VM was running?

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https://bugs.launchpad.net/bugs/1354167

Title:
  On VM restart: Could not open 'poppy.qcow2': Could not read snapshots:
  File too large

Status in QEMU:
  New

Bug description:
  I'm unable to restart a VM.   virt-manager is giving me:

  Error starting domain: internal error: process exited while connecting
  to monitor: qemu-system-x86_64: -drive
  file=/var/lib/libvirt/images/poppy.qcow2,if=none,id=drive-virtio-
  disk0,format=qcow2: could not open disk image
  /var/lib/libvirt/images/poppy.qcow2: Could not read snapshots: File
  too large

  
  From the command line trying to check the image also gives me:
  qemu-img check poppy.qcow2
  qemu-img: Could not open 'poppy.qcow2': Could not read snapshots: File too 
large

  
  This bug appears with both the default install of qemu for ubuntu 14.04:
  qemu-img version 2.0.0, Copyright (c) 2004-2008 Fabrice Bellard

  And the latest version.
  qemu-img version 2.1.50, Copyright (c) 2004-2008 Fabrice Bellard

  
  Host: 
  Dual E5-2650 v2 @ 2.60GHz
  32GB Memory
  4TB Disk space (2.1TB Free) 

  Host OS: Ubuntu 14.04.1 LTS 64bit

  Guest:
  Ubuntu 14.04 64bit
  Storage Size: 500gb

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