Re: [Qemu-discuss] Multiple snapshots with one guest user

[Alberto Garcia]

On Thu, Jan 19, 2017 at 03:20:33PM +0330, Mahmood Naderan wrote:
> May i ask what is the difference between the following commands
> 
> 1) qemu-img create -o backing_file base.img new.img 10G
> 2) qemu-img create -f qcow2 -b base.img new.img

There's several things here:

  # "-o backing_file=base.img" and "-b base.img" are equivalent.

  # In (1) you're missing the '=' in backing_file=base.img

  # If (1) you're also not specifying the file format, then it
    defaults to raw. But raw does not support backing files, so the
    command will not work.

  # qcow2 does support backing files, that's why (2) works.

Berto