On the web page: How to Install Ubuntu Server 14.04.1 on ESXi 5.5, vCenter Server installation on ESXi is a prerequisite:
Is that correct? vCenter seems to be OA&M software, is it required to get a Ubuntu 14.04.(3) 32-bit server VM?
Thanks and Best,
Yes, to clone a VM you need a vCenter Server, although you can copy the files and manually rename everything without a vCenter server but it is not as easy as right clicking on a VM and selecting Clone.
However, you do not need vCenter if you just want to create an Ubuntu Server but you will not be able to follow the guide in the link you posted word for word as it uses a the Web Client which is part of vCenter to do the work, you will need to perform similar operations using the vSphere client connected directly to your ESXi host.