If you want to learn virtualization, there are many avenues.

You can use Oracle VirtualBox, VMWare, KVM, Xen, HyperV, etc.

Since I was already familiar with other virtualization routes like Oracle VirtualBox, VMWare and HyperV, I decided to take the KVM plunge.

KVM stands for Kernel-based Virtual Machine and has been around since early 2007.

Before diving into KVM, first check if your CPU supports VT features in virtualization (Intel VT or AMD-V)

Use the below command to find whether your CPU supports VT features.

$ egrep '(vmx|svm)' /proc/cpuinfo
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf eagerfpu pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf eagerfpu pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm

As we can see from the above output, my CentOS 7.5 system has vmx.

So I’m good to go with KVM.

To manage the KVM virtual machines, I went ahead and installed the open source Virt Manager GUI for KVM.

Besides KVM, Virt-Manager is also said to support Xen and LXC (Linux Containers).

Here are the commands I used to install KVM on my CentOS 7.5 system.

$ sudo yum install -y qemu-kvm qemu-img virt-manager libvirt libvirt-python libvirt-client virt-install virt-viewer

Package 10:qemu-kvm-1.5.3-156.el7_5.5.x86_64 already installed and latest version
Package 10:qemu-img-1.5.3-156.el7_5.5.x86_64 already installed and latest version
Package bridge-utils-1.5-9.el7.x86_64 already installed and latest version
Resolving Dependencies
--> Running transaction check

[output truncated]

Good, you’ve now got KVM installed. It’s time to test it.

So I went and downloaded the lightweight Lubuntu 18.04.1.

If you’re on the Gnome 3.28 desktop, go to Applications—>System Tools—>Virtual Machine Manager.

This will open the Virtual Machine Manager and allow you to add whatever virtual machine you want to KVM.

I quickly attached Lubuntu 18.04.1 to KVM through the Virtual Machine Manager.

Voila, that’s it.

I was delighted that I had added one more item to my virtualization jewel-box.

The whole process of installing KVM and adding/updating Lubuntu took less than 15 minutes.

By the way, the above KVM installation was tested on CentOS 7.5 (kernel 3.10.0-862.11.6) running on an old Dell Optiplex 780SFF.

Useful Resources:
KVM
KVM on Wikipedia
Virt Manager

Anyone who has installed Oracle’s VirtualBox virtualization software inevitably encounters a few vexing problems.

The main problem is that your monitor settings (screen resolution) will be off and the desktop will not occupy the full screen.

Plus, there are usually issues with your mouse with the guest OS.

Here’s where the concept of Guest Additions comes into the picture.

Unless you install Guest Additions, you’ll continue to have problems with your installation of the guest OS under VirtualBox.

Guest Additions

So what exactly are Guest Additions?

Guest Additions are basically drivers for the guest OS and enabled shared folders.

Before installing Guest Additions, you must install a few prerequisites.

If you’re running CentOS, run the below command as root or sudo to install prerequisites like Dynamic Kernel Module Support, GNU Compiler Collection, etc on the guest OS.

# yum install gcc g++ dkms kernel-devel

Once the installation of dkms, gcc, etc is complete, open the VirtualBox VM for the guest OS, then select Devices tab in the top row, scroll down and pick the Insert Guest Additions option.

What happens now is that the Guest Additions ISO is mounted in the virtual CD drive of the virtual machine (guest OS). Continue reading »