virt-manager

Resources

virt-manager is a lightweight GUI application designed for managing virtual machines and containers via the libvirt API.

It provides a comprehensive view of all domains (VMs and containers), displaying their current state (running or inactive), along with real-time performance data and resource utilization stats. Users can easily create and configure new domains, storage, and network interfaces, while also reallocating host resources between guest domains as needed.

Primarily tailored for managing KVM-based VMs, virt-manager also supports Xen and LXC containers. The interface presents an overview of live domain performance, as well as resource allocation metrics.

Domain creation and configuration are streamlined with intuitive wizards, allowing for fine-grained control over resource allocation and virtual hardware settings.

For hands-on management, virt-manager includes an embedded VNC and SPICE client, providing full graphical console access to guest domains.

Overview

virt-manager serves as a powerful front-end for QEMU, providing an intuitive interface to manage virtual machines (VMs) and containers.

VM Management: virt-manager facilitates the creation, deletion, and maintenance of multiple VM instances.

Lifecycle Control: Start, stop, and manage the lifecycle of both VMs and containers with ease.

ISO Mounting: Attach and mount CD-ROM ISO images to VMs for installation or other purposes.

Networking Configurations: Configure various networking options for guest OS, including bridges, MACVLAN, static netdev, and NAT’ed IP interfaces.

Storage Pool Management: Create, delete, and maintain storage pools with support for a wide range of filesystems, including directory, direct hard drive, GlusterFS, iSCSI, LVM, multipath devices, netfs, SCSI, RADOS/Ceph, and Sheepdog.

For the main interface, the primary window of virt-manager offers a clear, concise overview of the VM and container environments, allowing users to manage resources and configurations efficiently.

Installation

BIOS/UEFI

Ensure that your host hardware has the necessary virtualization support by executing the following command:

host-platform-root#grep --color -E "vmx|svm" /proc/cpuinfo

The presence of the vmx (Intel) or svm (AMD) CPU flags should be highlighted in red, indicating that hardware virtualization is supported.

Additionally, verify that the /dev/kvm device file exists:

host-platform-root#ls /dev/kvm

/dev/kvm

Return back to QEMU for compliance.

USE flags

USE flags for app-emulation/virt-manager Desktop tool for managing libvirt virtual machines

`gui`	Enable support for a graphical user interface
`policykit`	Enable PolicyKit (polkit) authentication support
`sasl`	Enable connecting to SASL-enabled (e.g. Kerberos-protected) instances
`verify-sig`	Verify upstream signatures on distfiles

Data provided by the Gentoo Package Database · Last update: 2025-03-27 12:11 More information about USE flags

Note
If virt-manager is going to be used, be sure to enable the usbredir and spice USE flags on the qemu package for correct operation.

Emerge

root #emerge --ask app-emulation/virt-manager

Additional software

The virt-manager application requires the app-emulation/libvirt package for proper functionality. For installation instructions, refer to the libvirt documentation.

Configuration

Environment variables

The virt-manager command utilizes the following environment variables:


Environment variable name	Description
`HOME`	path of home directory.
`DISPLAY`	the display X server and screen to which graphical applications should be sent.
`WAYLAND_DISPLAY`	the display Wayland server and screen to which graphical applications should be sent.
`LANG`	the default system locale and language settings.
`LANGUAGE`	the user's preferred language(s) for software localization, overriding the default language defined by $LANG
`GSETTINGS_BACKEND`	which backend is used for the GSettings system, which is part of the GNOME configuration system. Valid values are dconf and memory.
`GSETTINGS_SCHEMA_DIR`	the directory where GSettings schemas are located.
`SSH_ASKPASS_REQUIRE`	controls whether SSH uses an external program to prompt for a password when accessing a remote system. When set to yes, SSH will require a password prompt and will use the SSH_ASKPASS program to request the password. When set to no, it disables the password prompt, allowing for key-based authentication or other non-interactive methods. Example: SSH_ASKPASS_REQUIRE=yes ensures that an SSH password prompt will be shown when needed.

Ensure these variables are correctly set in your environment for optimal operation of virt-manager.

Environment variables - Test

VIRTINST_TEST_SUITE
VIRTINST_TEST_SUITE_FORCE_LIBOSINFO
VIRT_MANAGER_DEFAULT_FORK

Files

The virt-manager command uses the following files:

$HOME/.cache/virt-manager/virt-manager.log
/proc/sys/kernel/cap_last_cap
/sys/devices/system/cpu/possible
/sys/devices/system/node/node0/meminfo
/sys/devices/system/node
$HOME/.cache/gstreamer-1.0/registry.x86_64.bin
$HOME/.config/dconf/user
$HOME/.config/gtk-3.0/colors.css
$HOME/.config/gtk-3.0/gtk.css
$HOME/.config/gtk-3.0/settings.ini
$HOME/.config/gtk-3.0/window_decorations.css
$HOME/.config/user-dirs.dirs
$HOME/.local/share/mime//mime.cache

User permissions

Usage

The virt-manager utility can be run in either system (root) or session (user) mode. For persistent domain operation, it is recommended to use system mode.

User-mode:

To run virt-manager in user mode, simply execute the following:

host-platform$virt-manager

System-mode:

For the system-mode, add the --connect=qemu:///system option to virt-manager command.

host-platform$virt-manager --connect=qemu:///system

Starting VM

To launch virt-manager, simply execute:

host-platform$virt-manager

To start virt-manager with the configuration window to gentoo guest, using default QEMU UNIX socket connection, run:

host-platform$virt-manager --connect qemu:///system --show-domain-editor gentoo

Shutting down VM

From the host platform:

Use Virtual Machine -> Shutdown in the virt-manager main menu bar.

From within the guest virtual machine:

Use Shutdown icon from the window manager (Start -> Shutdown).

Invocation

To view the full set of options and arguments available for virt-manager, run:

user $virt-manager --help

usage: virt-manager [options]

optional arguments:
  -h, --help            show this help message and exit
  --version             show program's version number and exit
  -c URI, --connect URI
                        Connect to hypervisor at URI
  --debug               Print debug output to stdout (implies --no-fork)
  --no-fork             Don't fork into background on startup
  --show-domain-creator
                        Show 'New VM' wizard
  --show-domain-editor NAME|ID|UUID
                        Show domain details window
  --show-domain-performance NAME|ID|UUID
                        Show domain performance window
  --show-domain-console NAME|ID|UUID
                        Show domain graphical console window
  --show-domain-delete NAME|ID|UUID
                        Show domain delete window
  --show-host-summary   Show connection details window

Also accepts standard GTK arguments like --g-fatal-warnings

Troubleshooting

virt-manager gui doesn't start or "virt-manager: command not found"

Version 4.1.0 changed USE flags, switching from gtk flag to gui. In order to (re)enable gui, the user must enable the gui flag before (re)build the package.

host-platform-root#echo "app-emulation/virt-manager gui" >> /etc/portage/package.use/app-emulation

no polkit agent available to authenticate action 'org.libvirt.unix.manage'

This usually results from the user not being in the libvirt group. Add the user to the group with:

host-platform-root#usermod -aG libvirt larry

QEMU/KVM not connected

Virt-manager uses libvirt as its backend to manage virtual machines. Therefore the libvirt daemon needs to be started.

host-platform-root#libvirtd

Or to start libvirtd at startup, add the daemon to the OpenRC runlevel / systemd target:

In OpenRC boot environment:

host-platform-root#rc-update add libvirtd default

In SystemD boot environment:

host-platform-root#systemctl enable libvirtd

'NoneType' object has no attribute 'conn'

This is typically a result in the cursor settings being misconfigured. The simplest fix is installing x11-themes/adwaita-icon-theme and updating gsettings to use the Adwaita cursor theme.

root #emerge --ask x11-themes/adwaita-icon-theme

host-platform$gsettings set org.gnome.desktop.interface cursor-theme "Adwaita"

Removal

root #emerge --ask --depclean --verbose app-emulation/virt-manager