On Mon, May 28, 2018 at 10:20:54PM +0100, Richard W.M. Jones wrote: > On Mon, May 28, 2018 at 08:38:33PM +0200, Kevin Wolf wrote: > > Just accessing the image file within a tar archive is possible and we > > could write a block driver for that (I actually think we should do > > this), but it restricts you because certain operations like resizing > > aren't really possible in tar. Unfortunately, resizing is a really > > common operation for non-raw image formats. > > We do this already in virt-v2v (using file.offset and file.size > parameters in the raw driver). > > For virt-v2v we only need to read the source so resizing isn't an > issue. For most of the cases we're talking about the downloaded image > would also be a template / base image, so I suppose only reading would > be required too. > > I also wrote an nbdkit tar file driver (supports writes, but not > resizing). > https://manpages.debian.org/testing/nbdkit-plugin-perl/nbdkit-tar-plugin.1.en.html
I should add the other thorny issue with OVA files is that the metadata contains a checksum (SHA1 or SHA256) of the disk images. If you modify the disk images in-place in the tar file then you need to recalculate those. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
