RedHat/CentOS: Install KVM Virtualization Kernel-based Virtual Machine

心心失意

　　KVM (Kernel-based Virtual Machine) is a  full virtualization solution for Linux on x86 hardware containing  virtualization extensions Intel VT or AMD-V. How do I install KVM under  CentOS or Red Hat Enterprise Linux version 5.5?
　　The Linux kernel 2.6.20 and above included KVM. RHEL 5.5 (and upcoming  RHEL 6) supports KVM out of box and it has also been ported to FreeBSD  as a loadable kernel module. However, this tutorial is tested on both  CentOS and RHEL 5.5 only running 64 bit Intel Xeon CPU (with Intel VT)  and 64 bit kernels with SELinux running in enforcing mode.
　　Why KVM?
　　XEN allows several guest operating systems to execute on the same  computer hardware and it is also included with RHEL 5.5. But, why use  KVM over XEN? KVM is part of the official Linux kernel and fully  supported by both Novell and Redhat. Xen boots from GRUB and loads a  modified host operating system such as RHEL into the dom0 (host domain).  KVM do not have concept of dom0 and domU. It uses /dev/kvm interface to  setup the guest operating systems and provides required drivers. See  the official wiki for more information.
　　Required Packages
　　You must install the following packages:
　　1. kmod-kvm : kvm kernel module(s)
　　2. kvm : Kernel-based Virtual Machine
　　3. kvm-qemu-img : Qemu disk image utility
　　4. kvm-tools : KVM debugging and diagnostics tools
　　5. python-virtinst : Python modules and utilities for installing virtual machines
　　6. virt-manager : Virtual Machine Manager (GUI app, to install and configure VMs)
　　7. virt-viewer: Virtual Machine Viewer (another lightweight app to view VM console and/or install VMs)
　　8. bridge-utils : Utilities for configuring the Linux Ethernet bridge (this is recommended for KVM networking)
　　KVM Package Group
　　RHEL comes with KVM software group which includes full virtualization  support with KVM. You can list all packages in the group as follows:
　　# yum groupinfo KVM
　　Sample outputs:
　　Loaded plugins: rhnplugin, security
　　Setting up Group Process
　　Group: KVM
　　Description: Virtualization Support with KVM
　　Mandatory Packages:
　　celt051
　　etherboot-zroms
　　etherboot-zroms-kvm
　　kmod-kvm
　　kvm
　　kvm-qemu-img
　　qcairo
　　qffmpeg-libs
　　qpixman
　　qspice-libs
　　Default Packages:
　　Virtualization-en-US
　　libvirt
　　virt-manager
　　virt-viewer
　　Optional Packages:
　　celt051-devel
　　etherboot-pxes
　　etherboot-roms
　　etherboot-roms-kvm
　　gpxe-roms-qemu
　　iasl
　　kvm-tools
　　libcmpiutil
　　libvirt-cim
　　qcairo-devel
　　qffmpeg-devel
　　qpixman-devel
　　qspice
　　qspice-libs-devel
　　A Note About libvirt
　　libvirt is an open source API and management tool for managing platform  virtualization. It is used to manage Linux KVM and Xen virtual machines  through graphical interfaces such as Virtual Machine Manager and higher  level tools such as oVirt. See the official website for more  information.
　　A Note About QEMU

　　QEMU is a processor emulator that>　　A Note About Virtio Drivers
　　Virtio is paravirtualized drivers for kvm/Linux. With this you can can  run multiple virtual machines running unmodified Linux or Windows VMs.  Each virtual machine has private virtualized hardware a network card,  disk, graphics adapter, etc. According to Redhat:
　　Para-virtualized drivers enhance the performance of fully  virtualized guests. With the para-virtualized drivers guest I/O latency  decreases and throughput increases to near bare-metal levels. It is  recommended to use the para-virtualized drivers for fully virtualized  guests running I/O heavy tasks and applications.
　　Host Operating System
　　Your main operating system such as CentOS or RHEL is known as host  operating system. KVM is a Linux kernel module that enables a modified  QEMU program to use hardware virtualization. You only need to install  KVM under host operating systems.
　　KVM Domains

　　It is nothing but a guest operating system running under host operating  system. Each kvm domain must have a unique name and>　　Guest Operating Systems
　　KVM supports various guest operating systems such as
　　1. MS-Windows 2008 / 2000 / 2003 Server
　　2. MS-Windows 7 / Vista / XP
　　3. FreeBSD
　　4. OpenBSD
　　5. Sun Solaris
　　6. Various Linux distributions.
　　7. NetBSD
　　8. MINIX
　　9. QNX
　　10. MS DOS
　　11. FreeDOS
　　12. Haiku
　　13. Amiga Research OS
　　Install KVM
　　Type the following command to install KVM under RHEL or CentOS:
　　# yum install kvm virt-viewer virt-manager libvirt libvirt-python python-virtinst
　　OR
　　# yum groupinstall KVM
　　Important Configuration And Log Files (Directories) Location
　　The following files are required to manage and debug KVM problems:
　　1. /etc/libvirt/ - Main configuration directory.
　　2. /etc/libvirt/qemu/ - Virtual machine configuration directory. All  xml files regarding VMs are stored here. You can edit them manually or  via virt-manager.
　　3. /etc/libvirt/qemu/networks/ - Networking for your KVM including  default NAT. NAT is only recommended for small setup or desktops. I  strongly suggest you use bridged based networking for performance.
　　4. /etc/libvirt/qemu/networks/default.xml - The default NAT configuration used by NAT device virbr0.
　　5. /var/log/libvirt/ - The default log file directory. All VM specific logs files are stored here.
　　6. /etc/libvirt/libvirtd.conf - Master libvirtd configuration file.
　　7. /etc/libvirt/qemu.conf - Master configuration file for the QEMU driver.
　　TCP/UDP Ports
　　By default libvirt does not opens any TCP or UDP ports. However, you can  configure the same by editing the /etc/libvirt/libvirtd.conf file.  Also, VNC is configured to listen on 127.0.0.1 by default. To make it  listen on all public interfaces, edit /etc/libvirt/qemu.conf file.