I have been using VirtualBox for the longest time when it comes to virtual machines, and never really felt like I needed anything more functionally. The only minor “issue” that I really noticed was the performance (boot time, latency, etc.) that I quickly dismissed once I got used to it. This is where QEMU comes into the picture, as it has existed as an alternative that offers superior performances, but at the cost of a more complicated setup process. For that reason, I had regrettably put it on the back burner for a while, until I finally gave it a try and was very surprised at how pleasant the installation process was. This guide was made mostly as a self-reminder, but also for anyone who are interested in trying QEMU & Virt-manager and are looking for a reasonably simple guide to get started.

Disclaimer: I’m still a Linux beginner as of the time of writing, so constructive criticisms are greatly appreciated. If anything, this should serves as a supplement to better, official documentations such as Arch Linux’s wiki for QEMU & Virt-manager, not to replace them.

Installation

Install the required packages. On Arch, qemu-desktop has only x86_64 emulation by default which is what I used, but can be replaced with qemu-full for the entire suite. For a minimal install, replace with qemu-base, but will require extra manual configurations for QXL/SPICE which will not be covered in this guide.

$ sudo pacman -S qemu-desktop virt-manager virt-viewer dmidecode dnsmasq bridge-utils iptables vde2 openbsd-netcat

Setup

Libvirt is the toolkit for managing virtualization platforms and is required for QEMU. Enable & start libvirtd.service, which will consequently do the same for libvirtd.socket.

$ sudo systemctl enable --now libvirtd.service

Add the current user to the libvirt group, otherwise Virt-manager will throw an error when trying to make a connection.

$ sudo usermod -a -G libvirt $(whoami)
$ newgrp libvirt

With this, you are ready to use QEMU! There are a few things you want to ensure are properly configured to everything to work:

  • QEMU/KVM > Details > Virtual Networks - Ensure virbr0 is Active (enable it if it isn’t).jj
  • If you have separate root & home partitions, it is recommended to add a new pool and set any directory in home for your VM disks to avoid using up root disk space. Go to QEMU/KVM > Details > Storage, click ‘Add Pool’ at the bottom left corner and change ‘Target path’ as desired.
  • As best practice suggested by the Arch wiki, ensure external directories outside the default pool are owned by libvirt-qemu group:
$ chown "$USER":libvirt-qemu /path/to/vm/folder

To create a new VM, just click the first icon in the toolbar and configure the settings as you would on other virtualization platforms.

Troubleshoot

  • VPN Blocking Connection: One problem I had was qemu:///system not being able to establish a connection since I was using a VPN. Libvirt’s virbr0 expects to route traffic from a specific subnet (which was 192.168.122.0/24 by default for me) through my actual internet connection, not my VPN tunnel. On Mullvad VPN, this can be fixed by enabling local network sharing (allowing network communication outside the tunnel to local ranges) or split tunneling (bypass the VPN tunnel entirely). These options may be different or unavailable on other VPN providers.
  • Firewall (UFW) Blocking Connection: Same problem as above, but with UFW (Uncomplicated Firewall) this time. A fresh Arch Linux setup should not have UFW, and upon install the firewall will block all incoming traffic by default. For the VM to communicate with our host, we need to allow traffic between virbr0 and the host machine by adding the following rules & :
$ sudo ufw allow in on virbr0
$ sudo ufw route allow in on virbr0 out on wlan0  
# change wlan0 to your network interface (check with `ip addr`)
# or wg0-mullvad for Mullvad VPN

An alternative to ufw route would be to just enable forwarding policy by default (from DROP to ACCEPT), though I prefer to keep default configurations and add individual rules instead.

/etc/default/ufw
DEFAULT_FORWARD_POLICY="ACCEPT"