[Thincrust-devel] issues with zip packaging for appliances

[Perry Myers]

I've been playing with the -p zip option to appliance-creator and ran into 
an issue that I'm not sure how we can solve...

If the output format of a disk image is raw there are two sizes, the 
logical size and the actual size.  So if I create a 20GB disk partition in 
the kickstart, but only use 1.5 GB the file appears to be 20GB but 
actually only takes 1.5GB on disk.

When appliance-creator attempts to add this disk image to the zip archive 
it fails because the logical size of the file is > 4GB which is the 
limitation of an individual file in a zip archive.  You can pass the 
allowZip64=True parameter to Zip in python to allow the zip64 extensions 
to remove this limitation, but then the zip file can no longer be 
extracted using the standard unzip command line tools (also not sure if 
native Windows zip can handle this)

It will probably be fairly common that appliance images will have logical 
sizes of > 4GB, so zip files are really only useful for packaging 
appliances if the image is qcow compressed instead of raw.  If the images 
are qcow, then the logical=actual and will generally be < 4GB.

We can consider using another archiving format like tar, but then we can't 
  extract appliances on Windows with the default tools there.  We can 
force qcow compression for zip packaging but that limits our hypervisor usage.

Thoughts on this?

Perry

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