[libvirt-users] Qemu restore error

[Dennis Householder]

Thanks for the prompt response Eric! The error I first posted was output 
from virt-manager after selecting restore on the GUI, and it was 
perpetual. The save files were 0 bytes in size, which probably qualifies 
them as being 'too short' :-). 'virsh start --force-boot' recovered the VMs.

For completeness sake, here is the 'virsh restore' output on the 0-byte 
savefile, as requested. The od command naturally returned all zeros.

virsh restore /var/lib/libvirt/qemu/save/JEMU-R3.save
error: Failed to restore domain from /var/lib/libvirt/qemu/save/JEMU-R3.save
error: operation failed: failed to read qemu header

Thanks for your help!

Dennis


On 12/15/2011 11:12 AM, Eric Blake wrote:
> On 12/15/2011 08:48 AM, Dennis Householder wrote:
>> Hello,
>>
>> I'm not sure if I am having a kvm/qemu issue, a virt-manager issue, or a
>> libvirt issue, so if I am asking the wrong crowd please let me know! In
>> short, restoring some suspended kvm guests via virt-manager is failing
>> because libvirt cannot read the qemu header. I cannot find any
>> documentation on what this means. From virsh's limited documentation I
>> was able to gather that there is probably something wrong with an xml
>> file somewhere, but I cannot find it. Any advice is greatly appreciated!
> This is the correct list; the error message comes from libvirt's
> qemuDomainSaveImageOpen() method, and implies that you have a corrupted
> save file (save files are created by 'virsh save' to a user-specified
> location, or by 'virsh managedsave' to a libvirt-maintained location;
> the libvirt-guests init script uses virsh managedsave as part of host
> shutdown).
>
>> Synopsis:
>> I have 5 KVM guests on a Fedora 16 laptop host. I manage them locally
>> through virt-manager. These guests are JUNOS 10.1R1 (installed over
>> FreeBSD 4.1 mini-inst) on a patched bios (SeaBIOS
>> pre-0.6.1-20100805_064324-Compaq8510w). One time I suspended my laptop
>> and the kvm domains were suspended as well. Trying to restore yields the
>> following error:
>>
>> Error restoring domain: operation failed: failed to read qemu header
> Are you restoring via 'virsh restore path/to/file', or are you just
> trying to start the guest with 'virsh start' or a similar action in
> virt-manager?
>
> If the former, then path/to/file is indeed corrupt; can you show us the
> size of that file, as well as 'od -N 128 -tx1z path/to/file'?
>
> If the latter, then you've uncovered a bug in the managedsave code
> (which I will be fixing shortly) - we attempt to detect and unlink
> corrupt managedsave files automatically, but in looking at the code, I
> see I missed a code path - if the file is corrupt because it is too
> short, then we fail to do the unlink(), making the problem perpetual.
> If this is the case, then please give me the same output as requested in
> the previous paragraph, but using /var/lib/libvirt/qemu/save/<dom>.save
> as the path/to/file.
>
> Then, after you have given me the details, you can work around the
> problem by doing 'virsh start --force' to force a fresh boot (the save
> file is already corrupt, so there is unfortunately no way to get the
> runtime state of the guest back to what it was when you suspended your
> host); hopefully your guest can fsck and recover gracefully from what
> was in the virtual disks at the time of the host suspend.
>

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