Without virtualisation, life at Linux Format towers would be a lot more complicated. Testing the DVD would be a nightmare, reviewing new distros would require us to wipe the machine on which we installed last issue’s distros, and if we wanted to test new software on different distros, we’d probably need yet more hardware and yet more time. Yet if you rewind back to the late Mesolithic LXF age – the early 2000s – these were exactly the kind of hardware logistics that the team had to wrangle, all the while living the wild lifestyle encouraged by the heady golden era of dead-tree publishing. Back then tech journalists were made of stronger stuff.
Nowadays things are much more straightforward. If you want to try a new OS, or even if you just want to do something a bit crazy with your current one, all you need do is fire up a virtual machine, and within minutes you have a device that for all intents and purposes behaves like a regular computer. Only you don’t need to worry about breaking it – anything you do can be undone, and no one will come at you with pointed questions/sticks if it breaks.
For beginners, a virtual machine is a great way to try Linux. You can run VirtualBox for free on Windows or macOS. If you’re already running Linux you may prefer to use Red Hat’s Virtual Machine Manager, which uses QEMU (an emulator) and KVM (Linux’s powerhouse of a hypervisor) behind the scenes. Whatever your tastes, we’ve got something for you.
Nobody can tell you what virtualisation is – you have to experience it for yourself. Or you could just read this…
Virtualisation has been around since the 1960s. Of course, computing then was all done on mainframes and OSes were a lot different, so it’s harder for youngsters to get their trendy heads around how this worked. The idea then is essentially the same as it is now: compute resources were to be shared (fairly) amongst users in such a way that concurrently running jobs would not interfere with one another. Operating system kernels used to be called ‘supervisors’, and each separate job was more or less its own entity (today we expect our OSes to multitask programs as a matter of course, but this wasn’t the case back then). So the underlying OS which governed these jobs was referred to as a hypervisor, a term still used today.
Modern hypervisors such as Xen and Microsoft’s Hyper-V are thin OSes that run on bare metal with the sole purpose of hosting guest VMs strictly and securely, much like the time-sharing schema of the mainframe days. These are called Type-1 hypervisors, which correctly implies the existence of Type-2 hypervisors. The latter, exemplified by VirtualBox, Parallels and QEMU run on a regular operating system and are probably more familiar to everyday users. Things are not binary, though; the Linux’s KVM (Kernel-based Virtual Machine) doesn’t fit nicely into either category, since it turns the kernel into something like a Type-1 hypervisor, but the host OS still runs as intended.
In 2006, Intel and AMD started shipping processors with, respectively, VT-x and AMD-V extensions. These enabled operating systems to run virtualised without modification, in contrast to previous approaches such as paravirtualisation (which modified the OS to run in a guest environment) or complex software workarounds. Since then, virtually (ahem) all desktop CPUs have shipped with these hardware virtualisation extensions. And they have evolved to enable not only faster virtualisation, but deeper too, with hardware interrupts, memory management units (MMUs) and onboard graphics – via Intel’s iGVT-g on Iris Pro graphics – now being virtualisable.
It’s even possible to blur the boundaries between physical and virtual; actual hardware can be handed off to a virtual machine and used seamlessly. A popular example of this is running a Windows 10 VM with a second (usually high spec) graphics card. This trick, known as PCIe passthrough, enables Linux users to play AAA games at very close to native speeds. PCIe and the general area of Virtual Function I/O (VFIO) require different CPU extensions, called VT-d on Intel and AMD-Vi on AMD. Some of Intel’s overclocker focused chips (the ones ending in K) lack these.
One new project worth keeping an eye on is Looking Glass (https://looking-glass.hostfission.com) which aims to streamline passthrough setup for Windows VMs. In particular, the need for a separate monitor and keyboard is obviated.
Learn the basics of virtualisation no matter which OS you’re running, or which OS you want to try.
One of the easiest ways to fire up your first virtual machine is with Oracle’s VirtualBox. This is free (GPL2-licensed) software available for Windows, macOS and Linux. Mac and Windows users should download it from https://virtualbox.org, and Linux users should install it with: $ sudo apt install virtualbox
It looks and works the same for all platforms, so no matter what your OS (or which OS you want to virtualise), you can make use of our handy six-step guide opposite. If you’re stuck for a distro to try, why not copy the Solus or OpenMandriva ISO files off the LXFDVD? If you were to tell VirtualBox to use it straight from the disc things would be awfully slow.
If you find yourself stuck in fullscreen mode, use Right Ctrl+F to return to windowed mode. If you find yourself with a mouse cursor trapped in the guest window, just press the Right Ctrl key to escape. Most Linux distributions today support seamless mouse integration, so the latter shouldn’t happen to you – taking the mouse past the edge of the screen in the guest should relinquish control to the host.
It’s straightforward to fire up a VM, but let’s look at some of the options VirtualBox provides to make your virtual life as smooth as your real one. First of all, if you store your virtual drive image on a traditional spinningrust hard disk, I/O-heavy workloads will be very slow and you’ll probably notice a lot of disk activity while they’re underway. For such tasks, and indeed if you’re brave enough to run a Windows VM, your life will be markedly better if you store the image on an SSD.
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