[Qemu-devel] [Bug 1524546] Re: qemu-img rebase error message mentions wrong file name

[Max Reitz]

The full story is that in 2015, qemu probably did not note that it
failed to open the overlay (<filename>) because it failed to open the
backing file.  It does that, now, though:

$ qemu-img rebase -b new.qcow2 top.qcow2 
qemu-img: Could not open 'top.qcow2': Could not open backing file: Could not 
open 'base.qcow2': No such file or directory

So that should be a fix.

Max

** Changed in: qemu
       Status: New => Incomplete

** Changed in: qemu
       Status: Incomplete => Fix Released

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https://bugs.launchpad.net/bugs/1524546

Title:
  qemu-img rebase error message mentions wrong file name

Status in QEMU:
  Fix Released

Bug description:
  While doing 'qemu-img rebase' for linking to a different backing file, if the 
old backing file does not exist, the command fails. During this failure, the 
error message shown is misleading.
  e.g. qemu-img rebase -b <backing_file> <filename> throws error saying "Could 
not open <filename>"
  Ideally it should "Could not open <old_backing_file>"

  snippet -
  address@hidden ~]# qemu-img info 
/opt/stack/data/nova/instances/94864a64-ebf8-45e6-a777-615921216a0a/disk
  image: 
/opt/stack/data/nova/instances/94864a64-ebf8-45e6-a777-615921216a0a/disk
  file format: qcow2
  virtual size: 20G (21474836480 bytes)
  disk size: 174M
  cluster_size: 65536
  backing file: /tmp/3559241a79b79ae663ec6e3d9b75d469967b383b
  Format specific information:
      compat: 1.1
      lazy refcounts: false
  address@hidden ~]# mv /tmp/3559241a79b79ae663ec6e3d9b75d469967b383b 
/tmp/3559241a79b79ae663ec6e3d9b75d469967b383a
  address@hidden ~]# file !$
  file /tmp/3559241a79b79ae663ec6e3d9b75d469967b383a
  /tmp/3559241a79b79ae663ec6e3d9b75d469967b383a: x86 boot sector; partition 1: 
ID=0x83, active, starthead 32, startsector 2048, 409600 sectors; partition 2: 
ID=0x8e, starthead 159, startsector 411648, 16365568 sectors, code offset 0xc0
  address@hidden ~]# file /tmp/3559241a79b79ae663ec6e3d9b75d469967b383b
  /tmp/3559241a79b79ae663ec6e3d9b75d469967b383b: cannot open (No such file or 
directory)
  address@hidden ~]# qemu-img rebase -b 
/tmp/3559241a79b79ae663ec6e3d9b75d469967b383a 
/opt/stack/data/nova/instances/94864a64-ebf8-45e6-a777-615921216a0a/disk
  qemu-img: Could not open 
'/opt/stack/data/nova/instances/94864a64-ebf8-45e6-a777-615921216a0a/disk': 
Could not open file: No such file or directory
  address@hidden ~]# 
  qemu-img version 1.5.3
  OS: RHEL7 - 3.10.0-229
  libvirtd (libvirt) 1.2.8

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