Basic KVM Virtual Machine Operations on AlmaLinux

Learn how to manage KVM virtual machines on AlmaLinux. This guide covers starting, stopping, resizing, networking, snapshots, and troubleshooting.
By İbrahim Korucuoğlu ( @siberoloji) |
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How to Perform Basic Operations on KVM Virtual Machines in AlmaLinux

Kernel-based Virtual Machine (KVM) is a powerful open-source virtualization platform that transforms AlmaLinux into a robust hypervisor capable of running multiple virtual machines (VMs). Whether you’re managing a home lab or an enterprise environment, understanding how to perform basic operations on KVM VMs is crucial for smooth system administration.

In this guide, we’ll cover essential operations for KVM virtual machines on AlmaLinux, including starting, stopping, managing storage, networking, snapshots, and troubleshooting common issues.

Why Choose KVM on AlmaLinux?

KVM’s integration into the Linux kernel makes it one of the most efficient and reliable virtualization solutions available. By running KVM on AlmaLinux, users benefit from a stable, enterprise-grade operating system and robust hypervisor capabilities.

Key advantages include:

  • Native performance for VMs.
  • Comprehensive management tools like virsh (CLI) and Virt-Manager (GUI).
  • Scalability and flexibility for diverse workloads.

Prerequisites

Before managing KVM VMs, ensure your environment is set up:

  1. KVM Installed:

  2. Virtual Machines Created:

  3. Access:

    • Root or sudo privileges on the host system.

Step 1: Start and Stop Virtual Machines

Managing VM power states is one of the fundamental operations.

Using virsh (Command Line Interface)

  1. List Available VMs: To see all VMs:

    sudo virsh list --all

    Output:

    Id   Name      State
-------------------------
-    testvm    shut off

  2. Start a VM:

    sudo virsh start testvm

  3. Stop a VM: Gracefully shut down the VM:

    sudo virsh shutdown testvm

  4. Force Stop a VM: If the VM doesn’t respond to shutdown:

    sudo virsh destroy testvm

Using Virt-Manager (GUI)

  1. Launch Virt-Manager:

    virt-manager

  2. Select the VM, then click Start to boot it or Shut Down to power it off.

Step 2: Access the VM Console

Using virsh

To access the VM console via CLI:

sudo virsh console testvm

To exit the console, press Ctrl+].

Using Virt-Manager

In Virt-Manager, right-click the VM and select Open, then interact with the VM via the graphical console.

Step 3: Manage VM Resources

As workloads evolve, you may need to adjust VM resources like CPU, memory, and disk.

Adjust CPU and Memory

Using virsh:

  1. Edit the VM configuration:

    sudo virsh edit testvm

  2. Modify <memory> and <vcpu> values:

    <memory unit='MiB'>2048</memory>
<vcpu placement='static'>2</vcpu>

Using Virt-Manager:

  1. Right-click the VM, select Details, and navigate to the Memory or Processors tabs.
  2. Adjust the values and save changes.

Expand Virtual Disk

Using qemu-img:

  1. Resize the disk:

    sudo qemu-img resize /var/lib/libvirt/images/testvm.qcow2 +10G

  2. Resize the partition inside the VM using a partition manager.

Step 4: Manage VM Networking

List Available Networks

sudo virsh net-list --all

Attach a Network to a VM

  1. Edit the VM:

    sudo virsh edit testvm

  2. Add a <interface> section:

    <interface type='network'>
  <source network='default'/>
</interface>

Using Virt-Manager

  1. Open the VM’s details, then navigate to the NIC section.
  2. Choose a network (e.g., NAT, Bridged) and save changes.

Step 5: Snapshots

Snapshots capture the state of a VM at a particular moment, allowing you to revert changes if needed.

Create a Snapshot

Using virsh:

sudo virsh snapshot-create-as testvm snapshot1 "Initial snapshot"

Using Virt-Manager:

  1. Open the VM, go to the Snapshots tab.
  2. Click Take Snapshot, provide a name, and save.

List Snapshots

sudo virsh snapshot-list testvm

Revert to a Snapshot

sudo virsh snapshot-revert testvm snapshot1

Step 6: Backup and Restore VMs

Backup a VM

Export the VM to an XML file:

sudo virsh dumpxml testvm > testvm.xml

Backup the disk image:

sudo cp /var/lib/libvirt/images/testvm.qcow2 /backup/testvm.qcow2

Restore a VM

  1. Recreate the VM from the XML file:

    sudo virsh define testvm.xml

  2. Restore the disk image to its original location.

Step 7: Troubleshooting Common Issues

  1. Issue: VM Won’t Start

    • Check logs for errors:

      sudo journalctl -xe

    • Verify resources (CPU, memory, disk).

  2. Issue: Network Connectivity Issues

    • Ensure the network is active:

      sudo virsh net-list

    • Restart the network:

      sudo virsh net-start default

  3. Issue: Disk Space Exhaustion

    • Check disk usage:

      df -h

    • Expand storage or move disk images to a larger volume.

Step 8: Monitoring Virtual Machines

Use virt-top to monitor resource usage:

sudo virt-top

In Virt-Manager, select a VM and view real-time statistics for CPU, memory, and disk.

Conclusion

Managing KVM virtual machines on AlmaLinux is straightforward once you master basic operations like starting, stopping, resizing, networking, and snapshots. Tools like virsh and Virt-Manager provide both flexibility and convenience, making KVM an ideal choice for virtualization.

With this guide, you can confidently handle routine tasks and ensure your virtualized environment operates smoothly. Whether you’re hosting development environments, testing applications, or running production workloads, KVM on AlmaLinux is a powerful solution.

Last modified 09.01.2025: msfconsoel translations ongoing... (f7e18da)