Resolving the “USB Redirection Error: Not Authorized” in KVM become simple with our latest blog. Bobcares, as a part of our Server Management Service offers solutions to every query that comes our way.

Overview

1. Resolving the “USB Redirection Error: Not Authorized” in KVM
2. Impacts of the Error
3. Causes and Fixes
4. Prevention Measures
5. Conclusion

Resolving the “USB Redirection Error: Not Authorized” in KVM

We may face the “USB redirection error: Not authorized” in KVM (Kernel-based Virtual Machine) environments can be frustrating, especially when USB devices are critical to the workflow. This error usually indicates that the user lacks the necessary permissions to redirect USB devices to a virtual machine. Let’s delve into its impacts, causes, and practical solutions to restore functionality.

Impacts of the Error

1. Inaccessibility of USB Devices: Users cannot access USB devices in virtual machines, hindering essential tasks.

2. Reduced Productivity: Inability to use peripherals like printers or USB drives can delay data transfer or critical tasks.

3. Limited Functionality: Applications relying on USB devices, such as scanners or specialized tools, may fail to work.

4. Challenges for Developers and Testers: Testing hardware-dependent applications becomes impossible without USB access.

5. Potential Security Risks: Users attempting unauthorized workarounds may unintentionally expose the system to vulnerabilities.

Causes and Fixes

1. Insufficient User Permissions: The user isn’t part of the necessary groups.

Fix: Add the user to the required groups (libvirt, kvm, qemu):

sudo usermod -aG libvirt,kvm,qemu

Replace with the actual username. Log out and log back in for changes to take effect.

2. PolicyKit Configuration: PolicyKit settings restrict USB access.

Fix: Modify the PolicyKit rule file:

sudo nano /usr/share/polkit-1/actions/org.spice-space.lowlevelusbaccess.policy

Update <allow_any> and <allow_inactive> to yes:

<allow_any>yes</allow_any>
<allow_inactive>yes</allow_inactive>

Save and restart services:

sudo systemctl restart libvirtd

3. USB Device Already in Use: The device is occupied by another process.

Fix: Identify and stop the process:

sudo fuser /dev/bus/usb//
sudo kill

Replace , , and with appropriate values from lsusb and the fuser command.

4. Incorrect USB Redirection Method: Using the wrong approach to attach USB devices.

Fix: Use the “Redirect USB device” option in the VM menu:

Start the VM.

Navigate to Virtual Machine Menu > Redirect USB Device.

5. Missing or Disabled Service: The libvirtd service isn’t running.

Fix: Start and enable the service:

sudo systemctl start libvirtd
sudo systemctl enable libvirtd

6. Device Filters in VM Configuration: Filters in the VM configuration block the USB device.

Fix: Edit the VM configuration using virsh:

sudo virsh edit

Locate <redirfilter> entries and adjust or remove restrictive filters. Ensure your USB device is allowed:

<redirfilter>
<usbdev allow=’yes’/>
</redirfilter>

Save the configuration and exit.

7. Driver Issues or Conflicts: USB drivers or services like pcscd interfere with the device.

Fix: Stop conflicting services:

sudo systemctl stop pcscd.socket
sudo systemctl stop pcscd

Prevention Measures

To avoid this error in the future, implement these strategies:

1. Regular updates ensure compatibility and security for virtualization software.

2. Ensure all relevant users are part of required groups for USB access.

3. Monitor and stop services that might conflict with USB redirection.

4. Keep records of any adjustments to PolicyKit or VM settings for troubleshooting.

[Need to know more? Get in touch with us if you have any further inquiries.]

Conclusion

Resolving the “USB redirection error: Not authorized” in KVM requires a methodical approach. By addressing permissions, configurations, and conflicts, we can restore USB device functionality and prevent future disruptions. This not only improves productivity but also ensures a seamless virtual machine experience.