KVM stands for Kernel Virtual Machine, a hypervisor which runs on Linux servers. This hypervisor is used by many in production, including multiple cloud providers.
KVM is actually made up two pieces: KVM and QEMU, though colloquially, the entire stack is generally simply refered to as “KVM”. KVM is the core kernel hypervisor module, and QEMU is an emulator along with the related userland components. They are closely intertwined but distinct software projects. Strictly speaking, QEMU could be run on it’s own, as an emulator, but KVM increases speed via hardware hypervisor functionality.
First, you must run a few pre-checks to ensure that your host properly supports all of the features to fully take advantage of VM hosting.
This ensures that your processor supports VT-x (Intel) or AMD-V (AMD), the hardware virtualization extensions. This outputs an integer: 0 means zero supported cores found, ` or more means your CPU supports these virtualization extensions.
egrep -c '(vmx|svm)' /proc/cpuinfo
Next, install the
sudo apt-get install -y qemu-kvm libvirt-bin virtinst bridge-utils cpu-checker
Additionally, you will probably want to install the following package, which provides
virt-* tools, which allow you to access guest disk images without booting the VM
virt-df, etc). These are not strictly required, however.
sudo apt-get install -y libguestfs-tools
Run the following command to ensure KVM is installed:
This should output
KVM acceleration can be used. If it does, you’ve successfully
By default, only root has permission to modify VMs. However, when using tools like
virt-manager remotely, you do not want to SSH as root, as this is insecure.
Instead, add any users needing to modify VMs to the
sudo usermod -aG libvirt [username]
This will not take affect until after the user’s session is restarted.
The user can check their own groups by simply running
groups, which outputs the groups
that the user is part of.
Additionally, you can run
groups [username] to check the group membership of another
You’re done and ready to run VMs. There are many management tools available for KVM,
virt-manager (GUI), and a host of web based tools.
By default, VMs will exist on a NAT network on the host - that is - they have internet access, but are not easily accessable from outside the host.
Most configurations use a bridge network - Checkout the next guide to set this up: