Running Kioptrix Level 4 on ESXi using vCenter Converter
For those of us running our own ESXi hosts, it can be useful to run our vulnerable VMs on them rather than on the same host as our pentest OS/tools, particularly if you want to simulate pentesting over additional switches, routers, firewalls etc.
I didn’t have any trouble running Kioptrix 1-3 on my ESXi host, but Kioptrix 4 gave the following “invalid disk type” error every time I attempted to boot up a newly created VM with the supplied .vmdk disk:
My understanding of this error is that the original .vmdk file supplied on the Kioptrix site (Kioptrix: Level 1.3 (#4) ~ VulnHub) was created in VMware Workstation, and as such has compatibility issues with ESXi.
Below is the VMware KB article on the error:
In the above article, there are two options; convert the VM in VMware Workstation via the VMware vCenter Converter, or reformat the .vmdk file using vmkfstools. Since the latter is detailed in the article already, I’m going to quickly document the vCenter Converter method.
First, mount the VM as you normally would in VMware Workstation.
Download the free VMware vCenter Converter Standalone from the below link:
VMware vCenter Converter Standalone – My VMware
Launch the converter, and click the Covert Machine icon: 
Select source type to be ‘VMware Workstation or other VMware virtual machine’, and browse to the location of the .vmx file from your currently mounted Kioptrix VM.
Select ‘VMware Infrastructure virtual machine’ as the destination type, and fill in the IP address and credentials of the ESXi host you want to migrate the VM to.
Give the destination VM a name and datastore location in the final screens and click Finish.
The task should only take a couple of minutes, and you should now have your VM ready to power on in ESXi.
As a side note; before doing the above process, I was able to get the Kioptrix #4 VM to boot as a newly created VM in ESXi by changing the Controller Location option in the VMs Hard Disk options to IDE. However, no matter what I tried, the powered on VM would not retrieve a DHCP address (including re-adding the network adapter as advised by the Kioptrix install guide). I’m not sure if the disk compatibility issue is related, but on doing the above conversion with vCenter Converter, the VM picked up a DHCP address on first boot.