My KVM howto

Enabling KVM support on your hardware

The host machines need to be running either Intel VT or AMD-V chipsets that support hardware-assisted
virtualization.

# grep -E 'vmx|svm' /proc/cpuinfo

If this command returns output, then your system supports KVM. The vmx CPU feature flag represents
Intel VT chipset while the svm flag represents AMD-V. Note which KVM flag was returned as it will be
useful for loading the right module later.

Next you need to ensure the KVM-related feature is enabled in the BIOS

1. In the BIOS menu, select Advanced Step → CPU Options.
2. Make sure the Intel Virtualization Technology option is Enabled.

Installing and configuring KVM-related package

Install the KVM software using yum:
# yum install kvm

Install additional virtualization management packages:

# yum install libvirt python-virtinst libvirt-python libvirt-client bridge-utils


Configuring KVM after installing the packages

After you have installed the KVM-related packages, load the right KVM modules by following these
steps:

Procedure
1. Insert KVM module by running the following command:
# modprobe kvm

2. Insert the chip-specific KVM module by running one of these commands:
For the AMD chip (svm flag)
# modprobe kvm-amd

For Intel chip (vmx flag)
# modprobe kvm-intel

You can verify that the modules are inserted and running.
# lsmod|grep kvm
kvm-intel    86248 3
kvm     223264 1 kvm_intel

3. Start the libvirtd daemon service:
# /etc/init.d/libvirtd start

Starting libvirtd daemon:
# /etc/init.d/libvirtd status
libvirtd (pid 6584) is running.

4. Set up libvirtd to start on every reboot:
# chkconfig libvirtd on

5. Better to reboot the host machine.


Creating LVM for Guest OS (Run lvdisplay before creating new LVM)

# lvcreate -L 4G -n kvm5 vg_kvm

-L 10G = replace with filesystem size
-n kvm1 = replace with kvm#

Creating KVM guest using virt-install

virt-install --name kvm1 \
--ram 512 \
--os-type='linux' \
--disk path=/dev/mapper/vg_kvm-kvm1 \
--network network:default \
--accelerate \
--vnc \
--cdrom /iso/CentOS-5.5-x86_64-bin-DVD-1of2.iso

For network installation replace --cdrom with --location with URL to OS installation link.

Eg, Centos 5.6 64bit
--location http://mirror.its.sfu.ca/mirror/CentOS/5.6/os/x86_64/

Creating Scientific Linux 6 64bit vm with bridge networking and two virtual CPUs

Note: br0 bridge interface should exist before using it for KVM

virt-install --name kvm3 \
--ram 1024 \
--vcpus 2 \
--os-type='linux' \
--disk path=/dev/mapper/vg_kvm-kvm3 \
--network bridge:br0 \
--accelerate \
--vnc \
--location http://ftp1.scientificlinux.org/linux/scientific/6/x86_64/os/


*** Installing Slackware off NFS (NFS running on xxx.xxx.xxx.60 machine)

virt-install --name slack64 \
--ram 512 \
--vcpus 1 \
--os-type='linux' \
--disk path=/dev/mapper/vg_kvm-kvm8 \
--network bridge:br0 \
--accelerate --vnc \
--cdrom /iso/slackware_x86_64-13.37-mini-install.iso

Cloning KVM VM
1. LVM based
Cloning KVM (Create LVM partition for cloned first ie 'lvcreate -L 4G -n kvmX vg_kvm' run lvdisplay to check existing LVMs)
virt-clone --original kvm1  \
             --name kvmX \
              --file /dev/mapper/vg_kvm-kvmX --prompt


2. File based
virt-clone --original kvm1  \
             --name kvmX \
              --file /var/lib/libvirt/images/centos6-2.img

Resizing KVM VM disk storage
1. install libguestfs-tools package.
2. Best to have separate parititons for /, /boot, and swap, then following http://askaralikhan.blogspot.com/2011/07/expanding-kvm-guest-disk-image-using.html


Troubleshooting For network interface

1. Open /etc/sysconfig/network-scripts/ifcfg-eth0 and delete the following line and save the file
HWADDR=52:54:00:8f:62:01
2. Remove the following filen and reboot the virtual machine
/etc/udev/rules.d/*persistent-net*'
After reboot eth0 network interface will be available.

Removing LVM partition: Remove LVM partition which is no longer need.


# lvchange -an /dev/mapper/vg_kvm-kvm8 (change LVM status to inactive)
# lvremove /dev/mapper/vg_kvm-kvm8 (remove the LVM paritition)