How to Deploy Multiple Virtual Machines using Network Install (HTTP, FTP and NFS) under KVM Environment Introduction

Introduction

Virtual machines (VMs) are a powerful tool for creating and managing multiple operating systems on a single physical machine. They allow you to run different operating systems, applications, and services without the need for additional hardware.

Instead of having multiple physical computers with their own dedicated resources, VMs share the resources of the host machine. Through this sharing of resources, VMs enable you to create isolated environments that can simulate different computing scenarios or test new software and applications without interfering with other processes.

Setting up the Environment

Installing KVM on the Host Machine

Before deploying multiple virtual machines, you need to have a host machine that can run the KVM environment. Installing KVM on your host machine is straightforward and can be done easily using your operating system's package manager. For example, if you are using a Debian-based distribution like Ubuntu, installing KVM can be done with a single command−

sudo apt-get install qemu-kvm libvirt-bin virtinst bridge-utils      

Once installed, you will have access to the virt-manager tool which allows you to manage virtual machines on your host machine with ease.

Creating a Virtual Network for the VMs

To deploy multiple virtual machines using network install in KVM environment, we need to create a virtual network that will act as a bridge between our host machine and the VMs. This means that all traffic going in and out of these VMs will pass through this virtual network. Creating this virtual network can also be done using virt-manager.

Simply go to File -> New Virtual Network and follow the wizard. You can choose to use NAT or bridged networking depending on your requirements.

Configuring DHCP and DNS Servers

Once our virtual network is created, we need to configure DHCP and DNS servers so that our VMs can get IP addresses and resolve domain names respectively. We can use either dnsmasq or ISC DHCP server for DHCP services.

In this article, we will use dnsmasq as it is lightweight and easy to configure. To install dnsmasq on Ubuntu −

sudo apt-get install dnsmasq       

Next, we need to configure dnsmasq by editing its configuration file located at /etc/dnsmasq.conf.

Here's an example configuration−

 interface=virbr0 dhcp-range=192.168.122.50,192.168.122.100,255.255.255.0,12h dhcp-option=option:router,192.168.122.1       

This configuration tells dnsmasq to listen on the virtual network interface virbr0, assign IP addresses in the range 192.168.122.50 to 192.168.122100 with a subnet mask of 255.2555..5.., and set the default gateway to be 192..1...68..1...22......1. To enable DNS resolution for our VMs, we can add the following line to /etc/dnsmasq.conf −

address=/example.com/192...16...8....2....58..        

This line maps all requests for example.com domain to IP address 192..16...8....2....58....

After configuring dnsmasq, restart it using−

sudo systemctl restart dnsmasq.service        

Preparing the Installation Media

Downloading and configuring HTTP, FTP, and NFS servers

Before deploying multiple virtual machines using network install in KVM environment, you need to download and configure HTTP, FTP, and NFS servers on your host machine. The installation media for these servers can be downloaded from their official websites or through package managers such as apt-get on Linux.

Once the installation is complete, you will have to configure them according to your system requirements. HTTP server is used for web-based installations while FTP server will work well if you prefer command-line or GUI-based installations.

On the other hand, Network File System (NFS) is a protocol that allows you to share files between hosts over a network. It can be used for centralizing installation media so that it can be accessed by multiple virtual machines at once.

Creating a custom kickstart file for automated installation

After downloading and configuring HTTP, FTP, and NFS servers on your host machine, the next step is to create a custom kickstart file for automated installations of virtual machines using network install. A kickstart file contains instructions on how the installation process should proceed without any human intervention. You can create a custom kickstart file by editing an existing one or by creating one from scratch using a text editor like vim or nano.

The contents of the kickstart file vary depending on what packages and configuration options are required during installation. It’s important to double-check that the syntax of your kickstart file is correct before deploying it because even small errors could cause issues during deployment of virtual machines using network install in KVM environment.

Deploying Virtual Machines using Network Install

Booting up virtual machines from network install media

After setting up the environment and preparing the installation media, it is time to boot up virtual machines from the network install media. In order to do this, we need to configure the virtual machine settings to boot from the network first.

This can be done by going into the settings of each virtual machine and selecting "Boot Options" and then choosing "Network Boot" as the first option. Once this is done, we can start up each VM.

During startup, each VM will look for a DHCP server on the network to obtain an IP address and other relevant information such as DNS server address and gateway address. The DHCP server will also provide a boot file (pxelinux.0) which will guide the VMs to load appropriate kernel image required for installation.

Configuring installation options using kickstart file

Once our virtual machines have booted up successfully from network install media, they will start loading kernel images required for OS installation process. At this point, we can specify our configuration options using kickstart files which are pre-configured files that automate OS installations. Kickstart files contain specific instructions regarding disk partitioning schemes; hostname; network interface configuration amongst others that will be applied during automated OS installations.

Kickstart files eliminate repetitive tasks during new installations while improving overall consistency of newly deployed systems. It is important to note that there are several tools available in creating custom kickstart files depending on your requirements such as ksvalidator or pykickstart packages in CentOS/RHEL distributions.

Monitoring installation progress

During the automated installation process, it's important to monitor each VM's progress closely so that any issues can be identified early before they become major problems requiring more significant intervention beyond troubleshooting tips or configurations tweaks. Logs generated during start-up and installation provide important debug information for troubleshooting.

It is important to ensure that each virtual machine has a unique hostname and IP address to minimize confusion during deployment. We can also use tools like virt-manager or Cockpit which provide graphical user interfaces that allow us to monitor the status of virtual machines in real-time.

Deploying multiple virtual machines using network install through KVM environment can significantly reduce the time and resources required for new system deployments. By following these steps, it's possible to deploy many VMs in a short amount of time with minimal human intervention while maintaining consistency across all deployed systems.

Conclusion

Deploying multiple virtual machines using network install in a KVM environment is an efficient and cost-effective way of managing multiple virtual machines. This article covered the importance of using this method, how to set up the environment, preparing the installation media, deploying virtual machines using network install and post-deployment configuration and management. We also looked at common issues encountered during deployment and how to troubleshoot them.