Citrix Xen uses a custom virtual appliance format for import/export called “XVA”. it’s basically a strangely crafted tar-file. You don’t need this program to unpack this tar-file, just use your favourite tar unpacker (tar, gtar, bsdtar). Once unpacked you will end up with a lot of different files, ova.xml (which contains the settings for the virtual appliance, think VMware vmx) and a number of folders called Ref:/, this is your disks. Each of these folders contain hundreds of files named 00000000, 00000001 with a accompanying .CHECKSUM file (SHA1). Each file is a 1MB slice of the disk, but some of the files in the sequence will probably be missing this is because XVA do not use compression; instead it will exclude slices of the disk that only contains zeros (are empty). This tool can assemble the disk for you (you will end up with a RAW disk) that can easily be mounted and modified. It can then also split the file again and generate checksum. Once ready, you will probably want to use the “package” command to rebuild the XVA file.

I’m running this conversion into a Debian 11 Server. First thing, you need to install xvz-img package from git repo into Debian server. Let’s install some essential package first-

apt install cmake g++ clang++ libssl-dev libxxhash-dev

Install qemu-utils

#Debian/Ubuntu
sudo apt-get install qemu-utils
#RHEL/CentOS/Fedora
sudo yum install qemu-kvm qemu-img

git clone https://github.com/eriklax/xva-img.git
cd xva-img/
cmake
make
make install

Extract the XVA file

mkdir my-virtual-machine
tar -xf my-virtual-machine.xva -C my-virtual-machine
chmod -R 755 my-virtual-machine

Extract one of the disks

xva-img -p disk-export my-virtual-machine/Ref\:1/ disk.raw

Splice the disk file (remove all files in the folder, required not to make any unnecessary mistakes)

rm -rf my-virtual-machine/Ref\:1/*
xva-img -p disk-import my-virtual-machine/Ref\:1/ disk.raw

Rebuild the XVA file

xva-img -p package my-virtual-machine-fixed.xva my-virtual-machine/ova.xml my-virtual-machine/Ref\:1/

Ref:

Convert Citrix Xenserver XVA Image to KVM

https://github.com/eriklax/xva-img