Kali is a Debian based distribution aimed at penetration testing. I haven’t felt a need to use it in the past because Debian has packages for all the scanning tools I regularly use, and all the rest are free software that can be obtained separately. But I recently decided to try it.
Here’s the URL to get Kali [1]. For a VM you can get VMWare or VirtualBox images, I chose VMWare as it’s the most popular image format and also a much smaller download (2.7G vs 4G). For unknown reasons the torrent for it didn’t work (might be a problem with my torrent client). The download link for it was extremely slow in Australia, so I downloaded it to a system in Germany and then copied it from there.
I don’t want to use either VMWare or VirtualBox because I find KVM/Qemu sufficient to do everything I want and they are in the Main section of Debian, so I needed to convert the image files. Some of the documentation on converting image formats to use with QEMU/KVM says to use a program called “kvm-img” which doesn’t seem to exist, I used “qemu-img” from the qemu-utils package in Debian/Bullseye. The man page qemu-img(1) doesn’t list the types of output format supported by the “-O” option and the examples returned by a web search show using “-O qcow2“. It turns out that the following command will convert the image to “raw” format which is the format I prefer. I use BTRFS for storing all my VM images and that does all the copy-on-write I need.
qemu-img convert Kali-Linux-2021.3-vmware-amd64.vmdk ../kali
After converting it the file was 500M smaller than the VMWare files (10.2 vs 10.7G). Probably the Kali distribution file could be reduced in size by converting it to raw and then back to VMWare format. The Kali VMWare image is compressed with 7zip which has a good compression ratio, I waited almost 90 minutes for zstd to compress it with -19 and the result was 12% larger than the 7zip file.
VMWare apparently likes to use an emulated SCSI controller, I spent some time trying to get that going in KVM. Apparently recent versions of QEMU changed the way this works and therefore older web pages aren’t helpful. Also allegedly the SCSI emulation is buggy and unreliable (but I didn’t manage to get it going so can’t be sure). It turns out that the VM is configured to work with the virtio interface, the initramfs.conf has the configuration option “MODULES=most” which makes it boot on all common configurations (good work by the initramfs-tools maintainers). The image works well with the Spice display interface, so it doesn’t capture my mouse, the window for the VM works the same way as other windows on my desktop and doesn’t capture the mouse cursor. I don’t know if this level of Spice integration is in Debian now, last time I tested it didn’t work that way.
I also downloaded Metasploitable [2] which is a VM image designed to be full of security flaws for testing the tools that are in Kali. Again it worked nicely after converting from VMWare to raw format. One thing to note about Metasploitable is that you must not make it available on the public Internet. My home network has NAT for IPv4 but all systems get public IPv6 addresses. It’s usually nice that those things just work on VMs but not for this. So I added an iptables command to block IPv6 to /etc/rc.local.
Conclusion
Installing VMs for both these distributions was quite easy. Most of my time was spent downloading from a slow server, trying to get SCSI emulation working, working out how to convert image files, and testing different compression options. The time spent doing stuff once I knew what to do was very small.
Kali has zsh as the default shell, it’s quite nice. I’ve been happy with bash for decades, but I might end up trying zsh out on other machines.