Complete Guide to KVM Virtualization on Ubuntu 24.04 LTS

Introduction

KVM (Kernel-based Virtual Machine) is a powerful open-source virtualization technology that transforms Linux into a type-1 (bare-metal) hypervisor. With Ubuntu 24.04 LTS, KVM provides enterprise-grade virtualization capabilities that rival proprietary solutions while maintaining the flexibility and cost-effectiveness of open source.

This comprehensive guide will walk you through setting up KVM on Ubuntu 24.04, creating virtual machines, and mastering essential management techniques. Whether you're building a home lab, deploying production workloads, or migrating from VMware, this tutorial provides everything you need to get started.

Prerequisites

Before installing KVM, ensure your system meets these requirements:

Hardware Requirements

CPU: 64-bit processor with hardware virtualization support
- Intel: VT-x (vmx flag)
- AMD: AMD-V (svm flag)
RAM: Minimum 4GB (8GB+ recommended)
Storage: At least 20GB free space for host OS and VMs
Network: Ethernet adapter for bridge networking

Verify Hardware Virtualization Support

Check if your CPU supports virtualization:

# Check for Intel VT-x or AMD-V support
egrep -c '(vmx|svm)' /proc/cpuinfo

# If the output is greater than 0, virtualization is supported
# For detailed CPU flags
lscpu | grep Virtualization

1. Installing KVM on Ubuntu 24.04

Step 1: Update System Packages

sudo apt update && sudo apt upgrade -y

Step 2: Install KVM and Related Packages

sudo apt -y install qemu-kvm libvirt-daemon-system libvirt-daemon virtinst bridge-utils libosinfo-bin

Package breakdown:

qemu-kvm: The main KVM hypervisor
libvirt-daemon-system: System daemon for managing VMs
libvirt-daemon: Virtualization management daemon
virtinst: Command-line tools for creating VMs
bridge-utils: Utilities for configuring network bridges
libosinfo-bin: Database of operating systems for optimal configurations

Step 3: Add User to Required Groups

# Add your user to libvirt and kvm groups
sudo usermod -aG libvirt $USER
sudo usermod -aG kvm $USER

# Apply group changes without logging out
newgrp libvirt
newgrp kvm

Step 4: Verify Installation

# Check if KVM modules are loaded

lsmod | grep kvm

# Verify libvirt service is running

sudo systemctl status libvirtd

# Test virsh command

virsh list --all

2. Configuring Bridge Networking

Bridge networking allows VMs to appear as physical hosts on your network, getting IP addresses from your DHCP server.

Step 1: Identify Your Network Interface

ip addr show

# Note your primary interface name (e.g., enp1s0, eth0)

Step 2: Configure Netplan for Bridge Networking

Edit your Netplan configuration:

sudo nano /etc/netplan/01-netcfg.yaml

Replace the content with:

network:
  ethernets:
    enp1s0:  # Replace with your interface name
      dhcp4: false
      dhcp6: false
  
  bridges:
    br0:
      interfaces: [enp1s0]
      dhcp4: false
      addresses: [10.0.0.30/24]  # Your static IP
      routes:
        - to: default
          via: 10.0.0.1  # Your gateway
          metric: 100
      nameservers:
        addresses: [10.0.0.10, 8.8.8.8]  # Your DNS servers
        search: [yourdomain.local]
      parameters:
        stp: false
      dhcp6: false
  version: 2

Step 3: Apply Network Configuration

# Apply the new configuration

sudo netplan apply

# Verify bridge creation

ip addr show br0

brctl show

3. Creating Your First Virtual Machine

Option 1: Command-Line Installation with virt-install

This method provides full control over VM creation:

# Create a directory for VM images

sudo mkdir -p /var/kvm/images

# Download Ubuntu 24.04 Server ISO
wget https://releases.ubuntu.com/24.04/ubuntu-24.04-live-server-amd64.iso

# Create VM with virt-install
sudo virt-install \
--name ubuntu-vm1 \
--ram 4096 \
--disk path=/var/kvm/images/ubuntu-vm1.img,size=20 \
--vcpus 2 \
--os-variant ubuntu24.04 \
--network bridge=br0 \
--graphics none \
--console pty,target_type=serial \
--location /path/to/ubuntu-24.04-live-server-amd64.iso,kernel=casper/vmlinuz,initrd=casper/initrd \
--extra-args 'console=ttyS0,115200n8'

Option 2: Using virt-manager GUI

For desktop users, install the graphical interface:

sudo apt install virt-manager

# Launch virt-manager

virt-manager

Understanding virt-install Parameters

Parameter	Description
`--name`	VM name (must be unique)
`--ram`	Memory allocation in MB
`--disk`	Disk configuration (path and size)
`--vcpus`	Number of virtual CPUs
`--os-variant`	OS type for optimization
`--network`	Network configuration
`--graphics`	Display type (none for headless)
`--console`	Console connection type

4. Essential VM Management Commands

Starting and Stopping VMs

# Start a VM

virsh start ubuntu-vm1

# Start and connect to console

virsh start ubuntu-vm1 --console

# Graceful shutdown

virsh shutdown ubuntu-vm1

# Force stop (use cautiously)

virsh destroy ubuntu-vm1

# Reboot VM

virsh reboot ubuntu-vm1

Listing and Monitoring VMs

# List running VMs

virsh list

# List all VMs (including stopped)

virsh list --all

# Show VM information

virsh dominfo ubuntu-vm1

# Display VM configuration

virsh dumpxml ubuntu-vm1

Console Access

# Connect to VM console

virsh console ubuntu-vm1

# Exit console: Ctrl + ]

Auto-start Configuration

# Enable auto-start

virsh autostart ubuntu-vm1

# Disable auto-start

virsh autostart --disable ubuntu-vm1

5. Storage Management

Creating Storage Pools

# Create a new storage pool directory

sudo mkdir -p /var/lib/libvirt/images/vmpool

# Define the storage pool

virsh pool-define-as vmpool dir - - - - "/var/lib/libvirt/images/vmpool"

# Start the pool

virsh pool-start vmpool

# Enable auto-start

virsh pool-autostart vmpool

# List storage pools

virsh pool-list --all

Managing Virtual Disks

# Create a new disk

virsh vol-create-as vmpool ubuntu-vm2.qcow2 30G --format qcow2

# List volumes in a pool

virsh vol-list vmpool

# Delete a volume

virsh vol-delete ubuntu-vm2.qcow2 --pool vmpool

6. Advanced VM Management Tools

Install Management Utilities

sudo apt -y install libguestfs-tools virt-top

Using libguestfs Tools

# List files in VM

virt-ls -l -d ubuntu-vm1 /etc

# View file content

virt-cat -d ubuntu-vm1 /etc/hostname

# Edit files in VM (while stopped)

virt-edit -d ubuntu-vm1 /etc/hosts

# Check disk usage

virt-df -d ubuntu-vm1

# Mount VM filesystem

sudo guestmount -d ubuntu-vm1 -i /mnt

sudo umount /mnt

Real-time Monitoring with virt-top

# Monitor VM performance

virt-top

# Sort by CPU usage: shift + P

# Sort by memory: shift + M

# Help: h

# Quit: q

7. VM Cloning and Snapshots

Cloning VMs

# Clone a VM

virt-clone --original ubuntu-vm1 --name ubuntu-vm2 --file /var/kvm/images/ubuntu-vm2.img

# Clone with auto-generated storage

virt-clone --original ubuntu-vm1 --name ubuntu-vm3 --auto-clone

Managing Snapshots

# Create snapshot

virsh snapshot-create-as ubuntu-vm1 --name "before-updates" --description "Clean install"

# List snapshots

virsh snapshot-list ubuntu-vm1

# Revert to snapshot

virsh snapshot-revert ubuntu-vm1 "before-updates"

# Delete snapshot

virsh snapshot-delete ubuntu-vm1 "before-updates"

8. Nested Virtualization

Enable nested virtualization to run VMs inside VMs:

Check Current Status

# For Intel

cat /sys/module/kvm_intel/parameters/nested

# For AMD

cat /sys/module/kvm_amd/parameters/nested

Enable Nested Virtualization

# For Intel CPUs

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

# For AMD CPUs

echo 'options kvm_amd nested=1' | sudo tee /etc/modprobe.d/kvm-amd.conf

# Reload module (Intel example)

sudo modprobe -r kvm_intel

sudo modprobe kvm_intel

Configure VM for Nested Virtualization

# Edit VM configuration

virsh edit ubuntu-vm1

# Add or modify CPU configuration:

<cpu mode='host-passthrough' check='none' migratable='on'/>

9. Performance Optimization

CPU Pinning

# Pin vCPUs to physical CPUs

virsh vcpupin ubuntu-vm1 0 0

virsh vcpupin ubuntu-vm1 1 1

Memory Optimization

# Set memory balloon

virsh setmem ubuntu-vm1 2048M --config

# Enable hugepages

echo 'vm.nr_hugepages = 1024' | sudo tee -a /etc/sysctl.conf

sudo sysctl -p

Disk I/O Optimization

Use VirtIO drivers and cache modes:

<disk type='file' device='disk'>

  <driver name='qemu' type='qcow2' cache='writeback' io='threads'/>

  <source file='/var/kvm/images/ubuntu-vm1.img'/>

  <target dev='vda' bus='virtio'/>

</disk>

10. Backup and Migration

Backup VMs

# Backup VM configuration

virsh dumpxml ubuntu-vm1 > ubuntu-vm1.xml

# Backup disk image

sudo cp /var/kvm/images/ubuntu-vm1.img /backup/

# Create compressed backup

sudo qemu-img convert -c -O qcow2 /var/kvm/images/ubuntu-vm1.img /backup/ubuntu-vm1-backup.qcow2

Live Migration (requires shared storage)

# Migrate to another host

virsh migrate --live ubuntu-vm1 qemu+ssh://dest-host/system

Troubleshooting Common Issues

VM Won't Start

# Check logs

journalctl -u libvirtd -f

# Verify VM configuration

virsh domblklist ubuntu-vm1

virsh domiflist ubuntu-vm1

# Check for errors

virsh start ubuntu-vm1 --console

Network Issues

# Verify bridge configuration

brctl show

ip addr show br0

# Check VM network

virsh domiflist ubuntu-vm1

virsh domifaddr ubuntu-vm1

Permission Issues

# Fix ownership
sudo chown -R libvirt-qemu:kvm /var/lib/libvirt/images/
# Check AppArmor
sudo aa-status

Security Best Practices

Regular Updates
sudo apt update && sudo apt upgrade
Firewall Configuration
sudo ufw allow 22/tcp sudo ufw enable
SELinux/AppArmor
- Keep security modules enabled
- Update policies as needed
Resource Limits
- Set CPU and memory limits
- Use cgroups for resource control
Network Isolation
- Use VLANs for network segmentation
- Implement firewall rules between VMs

Conclusion

KVM on Ubuntu 24.04 provides a robust, enterprise-ready virtualization platform that's both powerful and free. With features like live migration, snapshots, and nested virtualization, it rivals commercial hypervisors while maintaining the flexibility of open source.

Whether you're running a home lab, development environment, or production infrastructure, KVM offers the tools and performance needed for modern virtualization workloads. The combination of command-line tools and graphical interfaces makes it accessible to both beginners and advanced users.

As you continue your virtualization journey, explore advanced features like:

GPU passthrough for graphics-intensive workloads
SR-IOV for high-performance networking
Integration with cloud platforms like OpenStack
Automation with tools like Terraform and Ansible

With Ubuntu 24.04 LTS's five-year support cycle, you have a stable foundation for building and maintaining your virtualized infrastructure.