How to Use the Command 'virt-manager' (with Examples)

Virt-manager is a graphical utility that assists administrators and users in managing KVM (Kernel-based Virtual Machine), Xen virtual machines, and LXC (Linux Containers). Serving as a tool for both novice and experienced users, it simplifies complex virtualization tasks by offering a user-friendly interface. This command can be invoked using various arguments to address different management scenarios, from connecting to hypervisors to modifying virtual machine details. Below, we’ll explore practical examples of using virt-manager, offering a step-by-step guide to its versatile capabilities.

Use case 1: Launch the GUI

Code:

virt-manager

Motivation:

Starting the graphical user interface of virt-manager is the first step for users needing to visually manage virtual machines and containers. The graphical representation helps users efficiently navigate, initiate, and maintain VMs without delving into complex command-line tasks.

Explanation:

• virt-manager: This command, when executed without any arguments, launches the main interface of the virt-manager application. It is useful for beginners who prefer using GUIs over other complex command-line interfaces.

Example Output:

When you execute the command, the virt-manager window opens, displaying any previously configured virtual machines and available options for creating new ones or connecting to existing hypervisors.

Use case 2: Connect to a Hypervisor

Code:

virt-manager --connect hypervisor_uri

Motivation:

Connecting to a hypervisor is crucial for managing or creating virtual machines remotely. If you have multiple hypervisors in your setup (locally or across a network), you might need to specify the particular one you want to manage.

Explanation:

• --connect hypervisor_uri: This flag is followed by the URI of the hypervisor you intend to manage. The URI format typically specifies the type of connection protocol and the host, such as qemu:///system for a local QEMU hypervisor or something like xen+ssh://remotehost for a remote Xen hypervisor.

Example Output:

Upon successful connection, the virt-manager GUI updates to show the domains (virtual machines) running on the specified hypervisor, allowing you to interact with or modify them as needed.

Use case 3: Don’t Fork virt-manager Process into Background on Startup

Code:

virt-manager --no-fork

Motivation:

By default, virt-manager might fork and run as a background process. While this is generally beneficial for everyday usage, during debugging or development, running it in the foreground might give immediate feedback on command interactions or permit easier process management.

Explanation:

• --no-fork: This parameter retains the virt-manager process in the foreground, making it easier to monitor the output and errors directly in the terminal window, which can be essential for debugging purposes.

Example Output:

Instead of executing in the background, the application logs are shown directly in the terminal, which might include startup messages and error outputs if any arise during initialization.

Use case 4: Print Debug Output

Code:

virt-manager --debug

Motivation:

When encountering issues or unexpected behavior within virt-manager, enabling debug output allows users to receive detailed logs and messages that might pinpoint the source of errors or irregular performance.

Explanation:

• --debug: This flag enhances the verbosity of the output by including debugging information which can be crucial for troubleshooting problems related to virtual machine management and configurations.

Example Output:

The terminal displays detailed logs concerning every operation and step taken by the application, which can help in diagnosing faults or fine-tuning performance issues.

Use case 5: Open the “New VM” Wizard

Code:

virt-manager --show-domain-creator

Motivation:

For users frequently creating new virtual machines, having a swift option to directly launch the “New VM” wizard can save time and streamline the virtual environment setup process.

Explanation:

• --show-domain-creator: This argument directly invokes the wizard interface to guide users through the steps necessary to create a new virtual machine, including configuring resources and selecting source images.

Example Output:

The virt-manager window opens directly to the “New VM” wizard, beginning with selecting an installation method and proceeding through various configurations needed for creating a new virtual machine.

Use case 6: Show Domain Details Window for a Specific Virtual Machine/Container

Code:

virt-manager --show-domain-editor name|id|uuid

Motivation:

This use case relates to the need for viewing or adjusting the detailed configuration of a specific virtual machine or container. Easy access to these settings can help in managing resources, networking, or adjusting machine profiles without navigating through the GUI tree manually.

Explanation:

• --show-domain-editor: Activates the domain editor directly for a specific virtual machine.
• name|id|uuid: A specific identifier, either the name, ID, or UUID of the virtual machine or container, is specified to determine which machine’s details to display.

Example Output:

Upon execution, the domain editor window appears with detailed information and configuration options for the specified virtual machine, allowing edits to settings like CPU allocation, memory sizing, or virtual disk management.

Use case 7: Show Domain Performance Window for a Specific Virtual Machine/Container

Code:

virt-manager --show-domain-performance name|id|uuid

Motivation:

Monitoring the performance metrics of specific virtual machines is crucial for maintaining optimal configuration and preventing resource bottlenecks. It can detect whether the resources allocated are under or over-utilized, allowing for resource adjustments.

Explanation:

• --show-domain-performance: Opens the performance window for tracking metrics like CPU usage, memory consumption, or I/O operations.
• name|id|uuid: Directly identifies the machine or container whose performance you wish to monitor, using its name, numeric ID, or UUID.

Example Output:

The performance monitoring window appears, displaying real-time resource usage statistics for the identified virtual machine or container, potentially including graphs and historical data if supported.

Use case 8: Show Connection Details Window

Code:

virt-manager --show-host-summary

Motivation:

Viewing the connection details provides critical insights into the host’s setup, available resources, and overall system information. This can be important for validating configuration, troubleshooting, and understanding what capabilities might be possible with the current hypervisor setup.

Explanation:

• --show-host-summary: Activates a window displaying overarching information about the connected hypervisor, including details about available resources, system type, and potentially ongoing tasks.

Example Output:

A window emerges showing the summary of the host’s configuration, letting users immediately understand the capabilities and current resource allocation of their hosting environment, potentially illustrating CPU, memory, and storage capacity.

Conclusion:

The virt-manager command is a robust tool for managing virtual machines and containers. It serves a wide audience by offering numerous use-case specific commands, allowing users to tailor their experience based on individual needs and preferences. From simple tasks like launching a GUI to detailed performance monitoring or hypervisor connection, it remains an essential utility in the virtualization landscape.