How to Install KVM on AlmaLinux

Learn how to install KVM on AlmaLinux for powerful virtualization. This detailed guide covers setup, network configuration, and VM creation with KVM.

How to Install KVM on AlmaLinux: A Step-by-Step Guide

Kernel-based Virtual Machine (KVM) is a robust virtualization technology built into the Linux kernel. With KVM, you can transform your AlmaLinux system into a powerful hypervisor capable of running multiple virtual machines (VMs). Whether you’re setting up a lab, a production environment, or a test bed, KVM is an excellent choice for virtualization.

In this guide, we’ll walk you through the steps to install KVM on AlmaLinux, including configuration, testing, and troubleshooting tips.


What is KVM?

KVM (Kernel-based Virtual Machine) is an open-source hypervisor that allows Linux systems to run VMs. It integrates seamlessly with the Linux kernel, leveraging modern CPU hardware extensions such as Intel VT-x and AMD-V to deliver efficient virtualization.

Key Features of KVM:

  • Full virtualization for Linux and Windows guests.
  • Scalability and performance for enterprise workloads.
  • Integration with tools like Virt-Manager for GUI-based management.

Step 1: Prerequisites

Before installing KVM on AlmaLinux, ensure the following prerequisites are met:

  1. Hardware Requirements:

    • A 64-bit CPU with virtualization extensions (Intel VT-x or AMD-V).
    • At least 4 GB of RAM and adequate disk space.
  2. Verify Virtualization Support: Use the lscpu command to check if your CPU supports virtualization:

    lscpu | grep Virtualization
    

    Output should indicate VT-x (Intel) or AMD-V (AMD).

    If not, enable virtualization in the BIOS/UEFI settings.

  3. Administrative Access:

    • Root or sudo privileges are required.

KVM installation involves setting up several components, including the hypervisor itself, libvirt for VM management, and additional tools for usability.

  1. Update the System: Begin by updating the system:

    sudo dnf update -y
    
  2. Install KVM and Dependencies: Run the following command to install KVM, libvirt, and Virt-Manager:

    sudo dnf install -y qemu-kvm libvirt libvirt-devel virt-install virt-manager
    
  3. Enable and Start Libvirt Service: Enable the libvirtd service to start on boot:

    sudo systemctl enable libvirtd
    sudo systemctl start libvirtd
    
  4. Verify Installation: Check if KVM modules are loaded:

    lsmod | grep kvm
    

    Output should display kvm_intel (Intel) or kvm_amd (AMD).


Step 3: Configure Network Bridge (Optional)

To allow VMs to connect to external networks, configure a network bridge:

  1. Install Bridge Utils:

    sudo dnf install bridge-utils -y
    
  2. Create a Bridge Configuration: Edit the network configuration file (replace eth0 with your network interface):

    sudo nano /etc/sysconfig/network-scripts/ifcfg-br0
    

    Add the following content:

    DEVICE=br0
    TYPE=Bridge
    BOOTPROTO=dhcp
    ONBOOT=yes
    
  3. Edit the Physical Interface: Update the interface configuration (e.g., /etc/sysconfig/network-scripts/ifcfg-eth0) to link it to the bridge:

    DEVICE=eth0
    TYPE=Ethernet
    BRIDGE=br0
    BOOTPROTO=dhcp
    ONBOOT=yes
    
  4. Restart Networking:

    sudo systemctl restart network
    

Step 4: Create Your First Virtual Machine

With KVM installed, you can now create VMs using the virt-install command or Virt-Manager (GUI).

  1. Using Virt-Manager (GUI):

    • Launch Virt-Manager:
      virt-manager
      
    • Connect to the local hypervisor and follow the wizard to create a new VM.
  2. Using virt-install (Command Line): Create a VM with the following command:

    sudo virt-install \
      --name testvm \
      --ram 2048 \
      --disk path=/var/lib/libvirt/images/testvm.qcow2,size=10 \
      --vcpus 2 \
      --os-type linux \
      --os-variant almalinux8 \
      --network bridge=br0 \
      --graphics none \
      --cdrom /path/to/installer.iso
    

Step 5: Managing Virtual Machines

  1. Listing VMs: To see a list of running VMs:

    sudo virsh list
    
  2. Starting and Stopping VMs: Start a VM:

    sudo virsh start testvm
    

    Stop a VM:

    sudo virsh shutdown testvm
    
  3. Editing VM Configuration: Modify a VM’s settings:

    sudo virsh edit testvm
    
  4. Deleting a VM:

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

Step 6: Performance Tuning (Optional)

  1. Enable Nested Virtualization: Check if nested virtualization is enabled:

    cat /sys/module/kvm_intel/parameters/nested
    

    If disabled, enable it by editing /etc/modprobe.d/kvm.conf:

    options kvm_intel nested=1
    
  2. Optimize Disk I/O: Use VirtIO drivers for improved performance when creating VMs:

    --disk path=/var/lib/libvirt/images/testvm.qcow2,bus=virtio
    
  3. Allocate Sufficient Resources: Ensure adequate CPU and memory resources for each VM to prevent host overload.


Troubleshooting Common Issues

  1. Issue: “KVM Not Supported”

    • Verify virtualization support in the CPU.
    • Enable virtualization in the BIOS/UEFI settings.
  2. Issue: “Permission Denied” When Managing VMs

    • Ensure your user is part of the libvirt group:
      sudo usermod -aG libvirt $(whoami)
      
  3. Issue: Networking Problems

    • Check firewall settings to ensure proper traffic flow:
      sudo firewall-cmd --add-service=libvirt --permanent
      sudo firewall-cmd --reload
      

Conclusion

Installing KVM on AlmaLinux is a straightforward process that unlocks powerful virtualization capabilities for your system. With its seamless integration into the Linux kernel, KVM provides a reliable and efficient platform for running multiple virtual machines. By following this guide, you can set up KVM, configure networking, and create your first VM in no time.

Whether you’re deploying VMs for development, testing, or production, KVM on AlmaLinux is a robust solution that scales with your needs.