Re: [Qemu-devel] [PATCH 4/4][RFC] Add logic to QEMU to read command line options from qcow2 images

[dmc <dmc@filteredperception.org>]

Brian Wheeler wrote:
> On Thu, 2007-08-09 at 15:32 -0500, Anthony Liguori wrote:
>> Avi Kivity wrote:
>>> Anthony Liguori wrote:
>>>> If you're looking for a low-end solution, another possibility would 
>>>> be having a "new" file format which consisted of:
>>>>
>>>> #!/path/to/qemu [<args> ...] <nl>
>>>> <standard disk image>
>>>>
>>>> And then make the appropriate changes to QEMU such that it can skip 
>>>> the first line in a disk image file.  This has a few nice side 
>>>> effects.  The disk image is directly executable and it makes it very 
>>>> clear to the user that they have to trust the disk image.  The other 
>>>> nice thing is that it would work with file formats other than qcow2.
>>> Well, it would be nice to align the disk image to a sector boundary 
>>> (or, better, a page boundary).  But yes, a very good idea.
>> That has the very nice side effect of allowing you to edit the command 
>> line with a text editor provided you don't cross the sector boundary.  
>> Filling with spaces would be pretty nice.
>>
> 
> 
> Its a bad idea.  Either have a line terminated file, or a pure binary
> file, but don't mix them.  Besides firing up an editor to modify it
> being a royal pain, mystery breakages will occur when someone has their
> editor set to "insert mode" (which is the default) vs "overwrite mode"
> and doesn't notice those extra spaces moving beyond the 512-byte mark.

how about xml appended to image file, and size of xml appended to that? 
  And a tool to easily extract/replace the xml.  Just my $0.02...

-dmc