Virtualization with KVM

Introduction to KVM

KVM is a kernel module that provides hardware-assisted virtualization support on x86 hardware with virtualization extensions (Intel VT or AMD-V). It transforms the Linux kernel into a hypervisor, allowing it to run multiple virtual machines securely and efficiently.

KVM has several advantages over other virtualization solutions:

• Performance: KVM provides near-native performance for virtual machines due to hardware-assisted virtualization.
• Open-source: KVM is an open-source solution and part of the Linux kernel, making it free and accessible.
• Integration: KVM is tightly integrated with the Linux kernel, allowing for easy management and monitoring of virtual machines.
• Security: KVM leverages the Linux kernel’s built-in security features, providing a secure and isolated environment for virtual machines.

Installing KVM on Fedora Linux

Before you can use KVM on Fedora Linux, you need to ensure that your system meets the necessary hardware and software requirements.

Hardware Requirements

• A CPU that supports hardware virtualization (Intel VT or AMD-V)
• Sufficient RAM and storage space for the host system and virtual machines

To check if your CPU supports hardware virtualization, run the following command:

egrep -c '(vmx|svm)' /proc/cpuinfo

If the output is greater than 0, your CPU supports hardware virtualization.

Software Requirements

KVM is included in the Fedora Linux distribution by default, but you need to install a few additional packages:

1. Open a terminal and update the package lists:

   sudo dnf update
   

2. Install the required packages:

   sudo dnf install @virtualization
   

   This command installs the KVM hypervisor, QEMU emulator, and other necessary components.

3. Verify the installation by checking the KVM module status:

   lsmod | grep kvm
   

   You should see output similar to the following, indicating that the KVM module is loaded:

   kvm_intel             286720  0
   kvm                   690176  1 kvm_intel
   

Congratulations! You have successfully installed KVM on your Fedora Linux system.

Creating a Virtual Machine

Now that you have KVM installed, you can create and manage virtual machines. There are several ways to create and manage VMs with KVM, including command-line tools like virt-manager and virsh, as well as graphical tools like the GNOME Boxes application.

In this section, we’ll focus on using the virt-manager graphical tool, as it provides a user-friendly interface for managing virtual machines.

1. Install the virt-manager package:

   sudo dnf install virt-manager
   

2. Launch the virt-manager application from the application menu or by running the following command:

   virt-manager
   

3. In the virt-manager window, click on the “Create a new virtual machine” button.

4. Follow the wizard to configure your virtual machine:

   • Choose the installation source (ISO image, CDROM, or network install)
   • Set the RAM and CPU allocation for the virtual machine
   • Configure storage for the virtual machine (disk size and location)
   • Customize additional options like network configuration and video settings

5. Once you’ve completed the wizard, click the “Finish” button to create the virtual machine.

6. The virtual machine will start, and you can proceed with installing the guest operating system as you would on a physical machine.

During the installation process, you may be prompted to install additional drivers or software for better integration between the host and guest operating systems.

Managing Virtual Machines

After creating your virtual machines, you can manage them using the virt-manager application or the command-line virsh tool.

Using virt-manager

The virt-manager graphical tool provides a user-friendly interface for managing virtual machines. Here are some common tasks you can perform with virt-manager:

• Start, pause, and stop virtual machines
• View performance metrics like CPU, memory, and disk usage
• Take snapshots of virtual machines for backup or rollback purposes
• Attach additional storage devices or network interfaces
• Configure virtual machine settings like CPU, memory, and device allocation

Using virsh

The virsh command-line tool provides a more powerful and scriptable way to manage virtual machines. Here are some common virsh commands:

• virsh list - List all virtual machines and their states
• virsh start <vm-name> - Start a virtual machine
• virsh shutdown <vm-name> - Gracefully shut down a virtual machine
• virsh destroy <vm-name> - Forcefully stop a virtual machine
• virsh undefine <vm-name> - Remove a virtual machine definition from KVM
• virsh edit <vm-name> - Edit the XML configuration of a virtual machine

You can find more virsh commands and their usage by running virsh help or referring to the virsh manual pages.

Advanced KVM Configuration

While the default KVM configuration works well for most use cases, you may need to customize certain settings for advanced scenarios or specific workloads.

CPU and Memory Allocation

KVM allows you to allocate specific CPU and memory resources to virtual machines. You can configure these settings during virtual machine creation or modify them later using virt-manager or the virsh tool.

To modify CPU and memory allocation using virsh, run the following commands:

# Change CPU allocation
virsh setvcpus <vm-name> <number-of-cpus>

# Change memory allocation
virsh setmaxmem <vm-name> <memory-size>

Replace <vm-name> with the name of your virtual machine, <number-of-cpus> with the desired number of CPUs, and <memory-size> with the desired memory size (e.g., 4096M for 4 GB).

Storage Configuration

KVM supports various storage options, including file-based disk images, physical storage devices (LUNs), and networked storage (iSCSI, NFS). You can configure storage during virtual machine creation or add/remove storage devices later using virt-manager or virsh.

To add a new disk to a virtual machine using virsh, run the following command:

virsh attach-disk <vm-name> <source-path> <target-device> --persistent

Replace <vm-name> with the name of your virtual machine, <source-path> with the path to the disk image or device, and <target-device> with the target device name (e.g., vda, vdb).

Network Configuration

KVM supports various network configurations, including bridged networking, NAT (Network Address Translation), and virtual networks. You can configure network settings during virtual machine creation or modify them later using virt-manager or virsh.

To create a new virtual network using virsh, run the following command:

virsh net-define <network-xml-file>

Replace <network-xml-file> with the path to an XML file defining your network configuration.

Snapshots and Live Migration

KVM supports taking snapshots of virtual machines, which can be useful for backup or rollback purposes. You can create and manage snapshots using virt-manager or the virsh tool.

To create a snapshot of a virtual machine using virsh, run the following command:

virsh snapshot-create-as <vm-name> <snapshot-name> <description>

Replace <vm-name> with the name of your virtual machine, <snapshot-name> with a name for the snapshot,