Hi  everyone!
     I use the libvirt(version: 1.2.2) and QEMU(version: 2.2.1) to test qemu snapshot features:
    
     I tried virsh blockcommit when VM offline,  the virsh blockcommit failed: the error messase as below:
                          error: Requested operation is not valid: domain is not running
     when I start the VM,  the virsh blockcommit  work fine!
     my question is£ºwe need virsh support blockcommit when VM offline¡£how do£¿

    we  test qemu snapshot as follows£º
    we need  create  snapshot of the cycle£¬and  by virsh blockcommit merge snapshot chain£¬but when VM offline£¬ the virsh blockcommit will fail£¬ someone suggest me£ºwhen VM offline£¬may use qemu-img commit to submit snapshot turn£¬but qemu-img can't modify snapshot chain backing relation£¬it need we use qemu-img  rebase amend snapshot¡®s backingfile£¬ the main question is when we use qemu-img rebase modify snapshot's backingfile, if someone start the VM, it  will may lead to VM filesystem readonly¡£
  
   we  should how to  solve the question?   thanks!





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