Master KVM Virtualization on CentOS: A Complete Text‑and‑Image Guide

Master KVM Virtualization on Linux CentOS (Text + Images)

Preface

KVM turns the Linux kernel into a bare‑metal hypervisor, allowing multiple virtual machines (VMs) with independent operating systems and resources to run on a single physical host, improving hardware utilization, simplifying management, and reducing costs.

KVM Advantages

High Performance

Hardware Support : KVM leverages hardware virtualization extensions to deliver near‑native performance.

Kernel Integration : As a kernel module, KVM benefits from Linux’s performance optimizations and resource management.

Open‑Source & Cost‑Effective

Open Source : KVM is GPL‑licensed, free to use, modify, and distribute.

Community Support : An active open‑source community provides continuous improvements and support, lowering total ownership cost.

Flexibility

Multi‑OS Support : KVM runs various guest OSes, including Linux distributions, Windows, BSD, etc.

Compatibility : Seamlessly integrates with tools like QEMU and libvirt for powerful virtualization management.

Security

Kernel‑Level Security : Utilizes Linux security features (e.g., SELinux, cgroups) for strong isolation.

Resource Isolation : Each VM runs as an independent process, ensuring secure resource control.

Resource Management & Scalability

Dynamic Adjustment : CPU, memory, network, and storage can be adjusted on‑the‑fly.

Scalability : Easily expand the number of VMs and their resources to meet varying workloads.

KVM Disadvantages

Hardware Dependency

Hardware Requirements : Requires CPUs with virtualization extensions (Intel VT‑x or AMD‑V); unsupported hardware cannot run KVM.

Management Complexity

Learning Curve : Although tools like libvirt help, KVM’s configuration can be more complex than some commercial solutions.

Command‑Line Operations : Advanced features often need CLI commands, which may be challenging for newcomers.

Performance Overhead

I/O Overhead : While performance is close to native, I/O‑intensive workloads may experience some overhead.

Resource Contention : In resource‑constrained environments, multiple VMs may compete for CPU, memory, or I/O, degrading performance.

Summary of Pros : Strong isolation and security. Cons : Additional call overhead and lower resource utilization in some scenarios.

Deployment Tutorial

Configure local YUM source

If no packages are available, configure a network source.

CentOS 7 local source configuration

Configure Alibaba Cloud source for CentOS 7

Enable the options

Install required components

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

Check if CPU supports virtualization cat /proc/cpuinfo | grep vmx Verify KVM kernel modules

[root@localhost ~]# lsmod | grep kvm
kvm_amd               64937  0
kvm                  554609  1 kvm_amd
irqbypass             13503  1 kvm

Start and enable libvirtd service

[root@localhost ~]# systemctl start libvirtd
[root@localhost ~]# systemctl enable libvirtd

Edit bridge interface configuration (ifcfg‑br0)

vim /etc/sysconfig/network-scripts/ifcfg-br0
TYPE=Bridge
BOOTPROTO=static
NAME=br0
ONBOOT=yes
PREFIX=24
DEVICE=br0
IPADDR=192.168.180.139
GATEWAY=192.168.180.254
DNS1=202.96.134.133

Edit physical NIC (ifcfg‑ens33) to attach to the bridge

vim /etc/sysconfig/network-scripts/ifcfg-ens33
TYPE=Ethernet
BOOTPROTO=none
NAME=ens33
DEVICE=ens33
ONBOOT=yes
BRIDGE=br0

Launch virt-manager (GUI for libvirt)

virt-manager

Create Storage Pool

In virt‑manager, double‑click “QEMU/KVM”, select the “Storage” tab, and create a new pool (e.g., name it “bdqn_iso”, path “/data_kvm/iso”).

Create Storage Volume

Import ISO Image

Drag the ISO file into the newly created pool.

Create New Virtual Machine

Select the location of the ISO image.

Allocate Resources

Adjust CPU, memory, and other resources according to your host’s capacity.

Proceed with the remaining options and start the installation.

At this point the experiment is complete – a virtual CentOS 7 machine has been successfully created and is ready for installation.