Master Linux KVM: Step‑by‑Step Deployment with Commands & Screenshots

Overview

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

Advantages

High performance

Hardware support : KVM leverages CPU virtualization extensions (Intel VT‑x, AMD‑V) to deliver near‑native performance.

Kernel integration : As a kernel module it benefits from Linux’s optimizations and resource management.

Open‑source and cost‑effective

Open source : Distributed under the GPL, free to use, modify and redistribute.

Community support : Active community provides continuous improvements and reduces total cost of ownership.

Flexibility

Multi‑OS support : Runs various guest OSes such as Linux distributions, Windows, BSD.

Compatibility : Integrates with QEMU, libvirt and other tools for powerful management.

Security

Kernel‑level security : Uses SELinux, cgroups, etc., for strong isolation.

Resource isolation : Each VM runs as an independent process with controlled resources.

Resource management and scalability

Dynamic adjustment : CPU, memory, network and storage can be resized on‑the‑fly.

Scalability : Easy to add more VMs and adjust configurations for different workloads.

Disadvantages

Hardware dependency

Hardware requirements : Requires CPUs with virtualization extensions; cannot run on older hardware.

Management complexity

Learning curve : Tools like libvirt help, but configuration is more complex than some commercial solutions.

Command‑line operations : Advanced features often need CLI commands.

Performance overhead

I/O overhead : Near‑native speed but I/O‑intensive workloads may see some penalty.

Resource contention : Multiple VMs competing for resources can degrade performance.

Deployment tutorial

Configure a local YUM repository (or use the Alibaba Cloud mirror) to ensure required packages are available.

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

Check CPU virtualization support: cat /proc/cpuinfo | grep vmx Verify that the KVM kernel modules are loaded: lsmod | grep kvm Start and enable the libvirtd service:

systemctl start libvirtd
systemctl enable libvirtd

Edit the bridge interface configuration ( /etc/sysconfig/network-scripts/ifcfg-br0) with content similar to:

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 the physical NIC ( /etc/sysconfig/network-scripts/ifcfg-ens33) to attach it to the bridge:

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

Launch virt-manager, create a new storage pool (e.g., bdqn_iso) pointing to /data_kvm/iso, then create a storage volume for the VM disk.

Import the ISO image into the pool, and start a new VM wizard. Choose the imported ISO, allocate CPU and memory according to host capacity, and finish the installation of CentOS 7.

After the installation completes, a virtual CentOS 7 machine is ready for use.