Install QEMU and libvirt on Debian-based Systems

This guide offers detailed steps for installing and configuring KVM, along with QEMU and the libvirt software suite, on a Debian-based system. Since KVM kernel modules are already integrated into the Linux kernel, the installation process primarily involves setting up QEMU and libvirt.

KVM (Kernel-based Virtual Machine) is a virtualization module in the Linux kernel that enables the kernel to act as a Type-1 hypervisor. This functionality allows you to run guest operating systems at speeds nearly equivalent to the host machine.

QEMU is a generic and open source machine emulator and virtualizer. QEMU can emulate an entire system, including the CPU, memory, and other hardware components, but paired with KVM it can achieve near-native performance.

libvirt is a toolkit that provides a common API for managing virtualized environments.

What you’ll need

Το complete this guide, you will need the following:

A Debian-based system with root access.

Note

This project is tested on Debian 12 (Bookworm). It should work on other Debian-based distributions but it will require some modifications. We also plan to support Rocky Linux in the future.

Procedure

Follow the steps below to install QEMU and the libvirt software suite on your Debian-based system. The steps check if your CPU supports virtualization technology, install the required packages, and enable the libvirtd virtualization daemon.

Change to root user:
```
user:~$ sudo su -
root:~#
```
Check if your CPU supports virtualization technology. If virtualization is supported, the output should be greater than 0:
```
root:~# egrep -c '(vmx|svm)' /proc/cpuinfo
56
```

Check if KVM virtualization is supported:

root:~# kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used

Warning

If the kvm-ok utility is missing, install the cpu-checker package:

root:~# apt update && apt install -y cpu-checker

Install QEMU and the libvirt software suite:
```
root:~# apt update && \
    apt install -y qemu-system-x86 libvirt-daemon-system \
    virtinst virt-viewer ovmf swtpm qemu-utils guestfs-tools \
    libosinfo-bin tuned
```
This command will install the following packages:
- qemu-system-x86: An open-source emulator for hardware resources of a computer.
- libvirt-daemon-system: A daemon that manages virtual machines and the hypervisor, as well library calls.
- virtinst: A command-line tool for creating guest virtual machines.
- virt-viewer: A graphical console for connecting to a running virtual machine.
- ovmf: A set of firmware files for UEFI support in QEMU.
- swtpm: A TPM emulator for Virtual Machines.
- qemu-utils: A tool to create, convert, modify, and snapshot offline disk images.
- guestfs-tools: A set of extended command-line tools for managing virtual machines.
- libosinfo-bin: A library for managing OS information for virtualization.
- tuned: A system tuning service that optimizes system performance.
Enable and start the libvirtd virtualization daemon:
```
root:~# systemctl enable --now libvirtd
```
Enable the tuned service:
```
root:~# systemctl enable --now tuned
```

Find the default profile for the tuned service:

root:~# tuned-adm list
...
Current active profile: balanced

Optimize the system for virtualization:
```
root:~# tuned-adm profile virtual-host
```
Change back to your user account:
```
root:~# exit
user:~$
```

Add your user account to the kvm and libvirt groups:

user:~$ sudo usermod -aG kvm,libvirt $USER

Set the default libvirt URI to qemu:///system:

user:~$ echo "export LIBVIRT_DEFAULT_URI='qemu:///system'" >> ~/.bashrc

user:~$ . ~/.bashrc

Set the ACL for the default images directory:

a. Remove the existing ACLs:
```
user:~$ sudo setfacl -R -b /var/lib/libvirt/images
```
b. Grant regular user permission to the directory recursively:
```
user:~$ sudo setfacl -m u:$USER:rwx /var/lib/libvirt/images
```

Verify

Follow the steps below to verify that QEMU/KVM is correctly installed on your system, and launch the Virtual Machine Manager desktop application:

Verify that the libvirtd service is running:

user:~$ sudo systemctl status libvirtd
● libvirtd.service - Virtualization daemon
 Loaded: loaded (/lib/systemd/system/libvirtd.service; enabled; preset: enabled)
 Active: active (running) since Thu 2024-02-08 08:07:20 EET; 7h ago
...skipping...

Check that QEMU is correctly installed by querying its version:

user:~$ qemu-system-x86_64 --version
QEMU emulator version 7.2.9 (Debian 1:7.2+dfsg-7+deb12u5)
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers

Validate the host virtualization setup:

user:~$ sudo virt-host-validate qemu
QEMU: Checking for hardware virtualization                                 : PASS
QEMU: Checking if device /dev/kvm exists                                   : PASS
QEMU: Checking if device /dev/kvm is accessible                            : PASS
QEMU: Checking if device /dev/vhost-net exists                             : PASS
QEMU: Checking if device /dev/net/tun exists                               : PASS
QEMU: Checking for cgroup 'cpu' controller support                         : PASS
QEMU: Checking for cgroup 'cpuacct' controller support                     : PASS
QEMU: Checking for cgroup 'cpuset' controller support                      : PASS
QEMU: Checking for cgroup 'memory' controller support                      : PASS
QEMU: Checking for cgroup 'devices' controller support                     : PASS
QEMU: Checking for cgroup 'blkio' controller support                       : PASS
QEMU: Checking for device assignment IOMMU support                         : PASS
QEMU: Checking if IOMMU is enabled by kernel                               : PASS
QEMU: Checking for secure guest support                                    : WARN (Unknown if this platform has Secure Guest support)

Note

If you have an Intel CPU, you may see a warning about secure guest support. This is expected as it checks only for AMD and IBM processors.

Check the libvirt instance you are connected to:
```
user:~$ virsh uri
qemu:///system
```

Review the ACL permissions for the default images directory:

user:~$ getfacl /var/lib/libvirt/images
getfacl: Removing leading '/' from absolute path names
# file: var/lib/libvirt/images
# owner: root
# group: root
user::rwx
user:dimpo:rwx
group::--x
mask::rwx
other::--x
default:user::rwx
default:user:user:rwx
default:group::--x
default:mask::rwx
default:other::--x