I think you are refering to the VMware ESX and ESXi, ESX installs with a "OS" called service console which is based on linux, it allows you to install third party mgmt tools and things like that. ESXi is the almost same as ESX but without the "OS", hypervisor only. you need to pay for ESX, but ESXi is free, they both run on server class hardware.
Other options are VMware Workstation - not free, and VMware Server - free. These run on normal PC hardware
as far as CUCM testing goes, I don't think these products make much difference.
I am using VMware Workstation just because I already have it. I am pretty sure the free VMware Sever does the job just fine.
I'm running ESXi 4.0 on a DL580 server, we use the vSphere client to administrate the virtual machines, setup networking etc. It's all free and works a treat. Version 7 of cucm is also compatible with VMWare for lab purposes...
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.