Re: virsh list shows no vm after downgrade

Laine Stump <laine@xxxxxxxxx> · Fri, 19 Dec 2014 12:46:20 -0500



    On 12/18/2014 07:16 PM, Chengyuan Li
      wrote:

    
      Hi,
        

        I was running libvirt 1.2.2 and qemu 2.0 which are from
          icehouse cloud archive repo on ubuntu 12.04, "virsh list
          --all" showed correct instances after launching several VMs, 
        Then I just downgraded libvirt to 0.9.13 and qemu to
          1.0, but kept the VMs running. However, when I run "virsh list
          --all" after downgrade, I can't see any VMs. Seems that the
          old version libvirt 0.9.13 doesn't know the instances created
          by libvirt 1.2.2.
        

        Does anyone know how to solve this problem?
      
    
    Sometimes a new feature in the newer version of libvirt results in
    new attributes in the status or config XML that is unrecognized by
    the older libvirt when it is started. This can cause a parsing error
    when parsing the XML, and the result is that the domain in question
    isn't added to libvirt's list of domains.

    
    Between libvirt 0.9.13 and 1.2.2 (and qemu 1.0 --> 2.0) there
    were *a lot* of new features added. Especially if you constructed
    your guests while running the new libvirt/qemu, it's highly likely
    that such a downgrade is unfeasible, as required functionality will
    be missing in the older versions. Personally, I would never consider
    downgrading to something so old unless it was a complete necessity.

    
    If you really want to try staying with the older libvirt and qemu,
    take a look at the libvirtd log to see what error messages have been
    output. This will usually give you a clue about what parts of the
    XML aren't recognized. Unless it is for a feature that is truly
    required for that domain to run, you can hand-edit the files in
    /etc/libvirt/qemu/*.xml and /var/run/libvirt/qemu/*.xml to modify or
    eliminate the now-unrecognized bit of XML. (NB: this is the *only*
    time you will catch me recommending that you edit these files by
    hand! Normally you should never do anything with them directly, only
    via the libvirt API as the location and contents of these files are
    a private implementation detail of libvirt).

    
    After you've edited the files, restart libvirtd again and see if the
    problem still exists.

    
    If you do that above, I would strongly recommend making a copy of
    any file you edit, so that you can go back if things get messed up.

  
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