How to Create KVM Virtual Machines on AlmaLinux

How to Create KVM Virtual Machines on AlmaLinux: A Step-by-Step Guide

Kernel-based Virtual Machine (KVM) is one of the most reliable and powerful virtualization solutions available for Linux systems. By using KVM on AlmaLinux, administrators can create and manage virtual machines (VMs) with ease, enabling them to run multiple operating systems simultaneously on a single physical machine.

In this guide, we’ll walk you through the entire process of creating a KVM virtual machine on AlmaLinux. From installation to configuration, we’ll cover everything you need to know to get started with virtualization.

What is KVM?

KVM (Kernel-based Virtual Machine) is a full virtualization solution that transforms a Linux system into a hypervisor. Leveraging the hardware virtualization features of modern CPUs (Intel VT-x or AMD-V), KVM allows users to run isolated VMs with their own operating systems and applications.

Key Features of KVM:

• Efficient Performance: Native virtualization using hardware extensions.
• Flexibility: Supports various guest OSes, including Linux, Windows, and BSD.
• Scalability: Manage multiple VMs on a single host.
• Integration: Seamless management using tools like virsh and virt-manager.

Step 1: Prerequisites

Before creating a virtual machine, ensure your system meets these requirements:

1. System Requirements:

   • A 64-bit processor with virtualization extensions (Intel VT-x or AMD-V).
   • At least 4 GB of RAM (8 GB or more recommended for multiple VMs).
   • Sufficient disk space for hosting VM storage.

2. Verify Virtualization Support: Check if the CPU supports virtualization:

   lscpu | grep Virtualization
   

   If VT-x (Intel) or AMD-V (AMD) appears in the output, your CPU supports virtualization. If not, enable it in the BIOS/UEFI.

3. Installed KVM and Required Tools: KVM and its management tools must already be installed. If not, follow our guide on How to Install KVM on AlmaLinux.

Step 2: Preparing the Environment

Before creating a virtual machine, ensure your KVM environment is ready:

1. Start and Enable Libvirt:

   sudo systemctl enable libvirtd
   sudo systemctl start libvirtd
   

2. Check Virtualization Modules: Ensure KVM modules are loaded:

   lsmod | grep kvm
   

   Look for kvm_intel or kvm_amd.

3. Download the Installation Media: Download the ISO file of the operating system you want to install. For example:

   • AlmaLinux: Download ISO

Step 3: Creating a KVM Virtual Machine Using Virt-Manager (GUI)

Virt-Manager is a graphical tool that simplifies VM creation and management.

1. Launch Virt-Manager: Install and start Virt-Manager:

   sudo dnf install virt-manager -y
   virt-manager
   

2. Connect to the Hypervisor: In the Virt-Manager interface, connect to the local hypervisor (usually listed as QEMU/KVM).

3. Start the New VM Wizard:

   • Click Create a New Virtual Machine.
   • Select Local install media (ISO image or CDROM) and click Forward.

4. Choose Installation Media:

   • Browse and select the ISO file of your desired operating system.
   • Choose the OS variant (e.g., AlmaLinux or CentOS).

5. Allocate Resources:

   • Assign memory (RAM) and CPU cores to the VM.
   • For example, allocate 2 GB RAM and 2 CPU cores for a lightweight VM.

6. Create a Virtual Disk:

   • Specify the storage size for the VM (e.g., 20 GB).
   • Choose the storage format (e.g., qcow2 for efficient storage).

7. Network Configuration:

   • Use the default network bridge (NAT) for internet access.
   • For advanced setups, configure a custom bridge.

8. Finalize and Start Installation:

   • Review the VM settings.
   • Click Finish to start the VM and launch the OS installer.

Step 4: Creating a KVM Virtual Machine Using Virt-Install (CLI)

For users who prefer the command line, the virt-install utility is an excellent choice.

1. Create a Virtual Disk:

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

2. Run Virt-Install: Execute the following command to create and start the VM:

   sudo virt-install \
     --name testvm \
     --ram 2048 \
     --vcpus 2 \
     --disk path=/var/lib/libvirt/images/testvm.qcow2,size=20 \
     --os-type linux \
     --os-variant almalinux8 \
     --network bridge=virbr0 \
     --graphics vnc \
     --cdrom /path/to/almalinux.iso
   

   Replace /path/to/almalinux.iso with the path to your ISO file.

3. Access the VM Console: Use virsh or a VNC viewer to access the VM:

   sudo virsh list
   sudo virsh console testvm
   

Step 5: Managing Virtual Machines

After creating a VM, use these commands to manage it:

1. List Running VMs:

   sudo virsh list
   

2. Start or Stop a VM:

   • Start:

     sudo virsh start testvm
     

   • Stop:

     sudo virsh shutdown testvm
     

3. Edit VM Configuration: Modify settings such as CPU or memory allocation:

   sudo virsh edit testvm
   

4. Delete a VM: Undefine and remove the VM:

   sudo virsh undefine testvm
   sudo rm -f /var/lib/libvirt/images/testvm.qcow2
   

Step 6: Troubleshooting Common Issues

1. Issue: “KVM Not Found”:

   • Ensure the KVM modules are loaded:

     sudo modprobe kvm
     

2. Issue: Virtual Machine Won’t Start:

   • Check system logs for errors:

     sudo journalctl -xe
     

3. Issue: No Internet Access for the VM:

   • Ensure the virbr0 network is active:

     sudo virsh net-list
     

4. Issue: Poor VM Performance:

   • Enable nested virtualization:

     echo "options kvm_intel nested=1" | sudo tee /etc/modprobe.d/kvm.conf
     sudo modprobe -r kvm_intel
     sudo modprobe kvm_intel
     

Conclusion

Creating a KVM virtual machine on AlmaLinux is a straightforward process that can be accomplished using either a graphical interface or command-line tools. With KVM, you can efficiently manage resources, deploy test environments, or build a virtualization-based infrastructure for your applications.

By following this guide, you now have the knowledge to create and manage VMs using Virt-Manager or virt-install, troubleshoot common issues, and optimize performance for your virtualization needs.

Start building your virtualized environment with KVM today and unlock the potential of AlmaLinux for scalable and reliable virtualization.