You may or may not be aware if it, but an OVA file is just a tar archive containing an .ovf and a .vmdk files, respectively the VM configuration and disk.

$ ls *.ova HTAOE.ova $ tar tf HTAOE.ova HTAOE.ovf HTAOE-disk001.vmdk HTAOE.mf

So, you can simply extract the files:

Sometimes you may want to move a virtual machine in VirtualBox from one server to another. Once way of doing that is to export it from the command line.

1. Locate the virtual machine that you want to export (I’ll use the name UbuntuServer for the one to be exported and name the new one UbuntuServerNew), and then
2. Run the export command as follows:

$ vboxmanage export UbuntuServer -o UbuntuServerNew.ova

It is easy to convert a VirtualBox VDI image to a KVM qcow2 file. You have to use the RAW file format as an intermediate.

Make sure the VirtualBox machine is shutdown.

1. Convert the VDI to a raw disk image. Note: VDIs are compressed and raw images are not, so you will need to leave enough disk space for entire uncompressed disk. $ VBoxManage clonehd –format RAW vm.vdi vm.img
2. Then on your KVM host: $ qemu-img convert -f raw vm.img -O qcow2 vm.qcow2