Master KVM on CentOS: A Complete Step‑by‑Step Tutorial with Images

Overview

KVM (Kernel‑based Virtual Machine) turns the Linux kernel into a bare‑metal hypervisor, allowing multiple isolated virtual machines to run on a single physical host, improving hardware utilization and reducing cost.

Key Advantages

High performance : leverages hardware virtualization extensions for near‑native speed.

Open‑source & low cost : GPL‑licensed, free to use and modify.

Flexibility : supports many guest OSes (Linux, Windows, BSD) and integrates with tools like QEMU and libvirt.

Security : benefits from SELinux, cgroups and kernel‑level isolation.

Scalable resource management : dynamic CPU, memory, network and storage adjustments.

Drawbacks

Hardware dependency : requires CPUs with VT‑x/AMD‑V support.

Management complexity : command‑line heavy and steeper learning curve compared with commercial solutions.

Performance overhead : occasional I/O penalty and resource contention under heavy load.

Deployment Guide on CentOS 7

1. Prepare YUM repositories

If default repositories are unavailable, configure a local or Alibaba Cloud mirror.

2. Install required packages

yum install -y qemu-kvm qemu-kvm-tools virt-install qemu-img bridge-utils libvirt virt-manager

3. Verify CPU virtualization support

cat /proc/cpuinfo | grep vmx   # Intel

cat /proc/cpuinfo | grep svm   # AMD

4. Load and enable KVM modules

lsmod | grep kvm

5. Start and enable libvirtd service

systemctl start libvirtd
systemctl enable libvirtd

6. Configure a bridge network (br0)

Edit /etc/sysconfig/network-scripts/ifcfg-br0 with:

TYPE=Bridge
BOOTPROTO=static
NAME=br0
ONBOOT=yes
DEVICE=br0
PREFIX=24
IPADDR=192.168.180.139
GATEWAY=192.168.180.254
DNS1=202.96.134.133

Then modify the physical interface (e.g., ens33) to use the bridge:

TYPE=Ethernet
BOOTPROTO=none
NAME=ens33
DEVICE=ens33
ONBOOT=yes
BRIDGE=br0

7. Create storage pool and volume

Using virt-manager, create a pool named bdqn (path /data_kvm) and an ISO pool bdqn_iso (path /data_kvm/iso). Then create a storage volume for the VM.

8. Import ISO and create the VM

Drag the desired ISO into the bdqn_iso pool, start a new VM wizard, select the ISO, allocate CPU and memory according to host capacity, and finish the installation.

9. Allocate resources

Adjust CPU, memory, and storage based on your hardware specifications.

10. Complete installation

After the installer finishes, you will have a functional CentOS 7 virtual machine running under KVM.