Kernel based Virtulization.    Provided in all Linux type OS, with built in packages , like to jave KVM in RHEL6   yum install qemu-kvm qemu-img   These packages provide the user-level KVM emulator and disk image manager on the host Red Hat Enterprise Linux system    # yum install virt-manager libvirt libvirt-python python-virtinst libvirt-client       python-virtinst:    Provides the  virt-install  command for creating virtual machines.   libvirt:     to talk to RHEL KVM, via commands like "libvirtd" to VM mamager       #virt-mamager &      a graphical tool of KVM to manage the VMS     With virt-manager,  graphically step  by step wizard, you can create VMs, provide image , choose type of OS,.     Take snapshot, revert back on any image, it's like a VCenter.       #Daemon     #libvirtd        use other commands on host mamanger like        #virsh list --all   #virsh domaininfo <vmname> // info and confi of your vm          ...