To Download the iso-image of actual ESXi, you have to complete the free registration on vmware.com.
Registration is strict required otherwise you will be not able to download the installation media and the free license.
KVM, Kernel-based Virtual Machine, is a hypervisor built into the Linux kernel. It is similar to Xen in purpose but much simpler to get running.
Unlike native QEMU, which uses emulation, KVM is a special operating mode of QEMU that uses CPU extensions (HVM) for virtualization via a kernel module.
Extensible Messaging and Presence Protocol (XMPP) is an open XML technology for real-time communication, which powers a wide range of applications. Monitoring such as Icinga notifications or alive ping from a mobile phone.
Installation of ejabberd instant messaging server for XMPP: