As cloud computing technology matures, virtualization has become an indispensable part of data centers and enterprise IT infrastructure. KVM, as a mainstream open-source virtualization solution, is widely popular due to its high performance and good Linux integration. This article will discuss the installation methods for virtual machines in Centos7 and management using the virt-install tool.

Overview of KVM Virtualization Technology

KVM (Kernel-based Virtual Machine) is a kernel-based virtualization technology that turns the Linux kernel into a type manager (hypervisor), allowing users to run multiple virtual machines on a single physical machine. Compared to other virtualization solutions, one of KVM’s advantages is its natural integration into the Linux kernel, providing better performance and lower latency.

The Relationship Between KVM and QEMU

While KVM provides virtualization support for the CPU and memory of virtual machines, it requires QEMU to emulate IO devices and provide user-space management. In short, KVM is responsible for providing hardware-accelerated virtualization support, and QEMU is responsible for emulating peripheral devices. Together, they offer a complete virtualization solution.

Steps to Install KVM on Centos7

Before installing KVM on Centos7, you need to ensure the following conditions are met:

Check if the CPU Supports Virtualization

Your CPU must support hardware virtualization technology (Intel VT or AMD-V). Run the following command to check whether the CPU has virtualization capabilities:

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

If the vmx (Intel) or svm (AMD) flags appear, it means your CPU has virtualization capabilities.

Enable Virtualization Options in BIOS

Enable the CPU’s virtualization feature in the BIOS settings, which is a necessary condition for using KVM.

Install KVM and Related Tools

Next, you need to install KVM and its related tool packages. In Centos7, use the following command to install the required packages:

yum install -y qemu-kvm libvirt virt-install bridge-utils

Creating and Managing KVM Virtual Machines

After installing the related tools, you can start creating and managing KVM virtual machines.

Creating a Virtual Machine Disk

Use the qemu-img command to create a virtual disk:

qemu-img create -f qcow2 /var/lib/libvirt/images/centos7.qcow2 20G

The above command will create a virtual disk file named centos7.qcow2, with a size of 20GB, in the /var/lib/libvirt/images/ directory.

Creating a Virtual Machine with virt-install

Create a new virtual machine instance using the virt-install command:

virt-install --virt-type kvm \
--name centos7vm \
--ram 2048 \
--vcpus 2 \
--os-variant centos7.0 \
--cdrom=/path/to/your.iso \
--network bridge=br0,model=virtio \
--graphics none \
--disk path=/var/lib/libvirt/images/centos7.qcow2,size=20,bus=virtio,format=qcow2