Generating Virtual Machines within DaDesktop via Virt Manager

Introduction

When preparing training materials, it is common to virtualize a server within DaDesktop, and in some cases, one or two client machines as well. This setup can involve a homogeneous operating system environment or a mixed Windows/Linux configuration.

Creating 'Nested VMs' can be achieved using Virt Manager or VirtualBox, with Vagrant optionally used for Linux environments, or VirtualBox if the DaDesktop host is running Windows 10.

Following rigorous testing, our recommended approach is to use Virt Manager, as VirtualBox presents several bugs in this context; consequently, we currently advise against using VirtualBox for this specific purpose.

The VirtManager application leverages the libvirt library to deliver virtual machine management services. It features a desktop interface that facilitates the creation, deletion, and administration of multiple virtual machines. While it is primarily designed for KVM VMs, it also supports other hypervisors such as Xen and LXC.

Virt Manager also integrates seamlessly with Vagrant, simply by installing the necessary library :        

apt install vagrant-libvirt

It is worth noting that while fewer Vagrant boxes are natively available for libvirt/kvm compared to VirtualBox, these can be easily converted to work with libvirt as demonstrated here : 

https://medium.com/@gamunu/use-vagrant-with-libvirt-unsupported-boxes-12e719d71e8e
 

The user interface offers a comprehensive overview of all VMs, including their status, CPU utilization, live performance graphs for active VMs, and resource usage statistics.

If you are new to Virt Manager, note that it is very similar to VirtualBox but includes several important distinctions detailed below.

This is a solid guide regarding the use of virt-manager on Ubuntu Linux - https://www.debugpoint.com/virt-manager/

 

Why should I choose Virt Manager over VirtualBox?

Advantages

1. Superior performance - Virt Manager utilizes VirtIO drivers for storage, networking, and graphics, which significantly enhances performance. Virtio drivers are KVM's paravirtualized device drivers, available for Linux and Windows guest virtual machines running on KVM hosts. The virtio package supports block (storage) devices, network interface controllers, and graphics. Since VirtIO drivers are open source, they can be easily installed if not already pre-installed on your Linux distribution.
2. Greater configurability options
3. Excellent compatibility with Vagrant
4. Parts of VirtualBox are not fully open source
5. Virt Manager does not require module recompilation after kernel upgrades, unlike VirtualBox.
6. VirtualBox is occasionally known to break following kernel upgrades.

Disadvantages

1. VirtualBox may have a slightly gentler learning curve
2. Configuring 'Host networking' instead of NAT is simpler in VirtualBox, although NAT functions adequately for most networking scenarios in both systems.
3. VirtualBox is available across many platforms, whereas Virt Manager is exclusive to Linux

Overall, we find Virt Manager to be the preferred choice for running servers within a DaDesktop machine.

 

Installation

Since libvirt is continuously improving, it is best to use the latest non-LTS Ubuntu or Debian version.

To install kvm and virt-manager, refer to these brief notes; however, always follow an up-to-date guide for your specific DaDesktop OS. One such guide can be found at https://www.debugpoint.com/virt-manager/

sudo apt install virt-manager

sudo adduser student libvirt
sudo systemctl restart libvirtd

Reboot the DaDesktop machine, then launch Virt Manager from the Applications menu

 

Configuration

1. How can I import or convert virtual machines ? While creating VMs tailored to your OS and specification requirements is straightforward, complex setups often benefit from importing an existing VM configuration for a specific server or appliance. These are frequently provided as VMDK images, which can potentially be added directly to Virt Manager, although this capability is not fully clear in current versions. VirtualBox server images cannot be imported directly but can be easily exported to other virtualization formats, such as Open Virtualisation Format (.OVF), which Virt Manager supports. Alternatively, you may use VmWare Convertor (if available) or Virt-V2V (https://www.redhat.com/en/blog/importing-vms-kvm-virt-v2v). Qemu-convert is also an excellent open-source tool for converting between different virtual machine formats.
   To Convert from VirtualBox to Virt Manager KVM format, follow these instructions https://ostechnix.com/how-to-migrate-virtualbox-vms-into-kvm-vms-in-linux/

2. The most efficient method for importing large files into a standalone environment. Recently, functionality to easily upload files from your host machine to your DaDesktop machine has been added.

   Otherwise, consider utilizing Cloud file services such as Google Drive, Microsoft 365, etc. These services can be accessed by logging in within the DaDesktop machine.

3. When importing virtual machines from other formats, you will often need to modify graphics and/or disk types.  A significant benefit of Virt Manager is its robust support for VirtIO drivers. These open-source, fully virtualized drivers offer significantly better performance compared to standard disk, network, or graphics drivers and are available for nearly all operating systems, including excellent support for guest Windows 10 machines. If your Guest OS supports them, VirtIO drivers are usually the preferred choice for compatibility and performance when using Virt Manager (KVM). https://wiki.archlinux.org/title/Libvirt
4. Optimal settings for virtual machines using Virt Manager VirtIO drivers are included in almost all modern open-source server operating systems and can be easily installed on Windows. While virtio drivers are generally the best option, there are cases where other types may be necessary. NAT is sufficient for most networking needs, unless a complex setup requiring Bridged Host networking is needed, which is typically more challenging to configure. 
   https://wiki.archlinux.org/title/Virt-manager serves as an excellent introductory guide.
   Running Windows requires additional steps, including the slipstreaming of VirtIO drivers to ensure the Windows 10 ISO can boot successfully.
   Regarding hard disk format selection, .raw files offer the best speed unless snapshots are required; in that case, use qcow2 format, which is slightly slower.
5. Although Wayland functions well as a display manager in most scenarios, we advise continuing to use X11 for the time being. However, it may be worth testing Wayland in your specific setup, as distributions are continuously improving their Wayland support.
6. There is no need to use KSM, as although it works in nested and Virt Manager environments, it provides minimal practical benefit.
7. Tech Support is available if you require assistance converting disk images for use with Virt Manager, as well as for setting up Virt Manager for DaDesktop courses.

8. Where are disk image files stored within the filesystem? Virt Manager uses the following default location for image files, though this is configurable and other locations may be preferred.

   /var/lib/libvirt/images