I'm struggling to connect a usb device, that gets detected correctly by the host, to a kvm vm.

I have a freshly installed Ubuntu Server 14.10 as KVM/QEMU host. I set up an Ubuntu vm using this command:

virt-install --connect qemu:///system \
            -n test01 \
            -r 1024 \
            --vcpus=2 \
            --disk path=/vmstorage/01/test01.img,size=5 \
            --vnc \
            --noautoconsole \
            --os-variant=ubuntuutopic \
            --hvm \
            --cdrom /path/to/ubuntu-14.10-server-i386.iso

After the successful installation a virsh dumpxml test01 returns

<domain type='kvm' id='16'>
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
  <vcpu placement='static'>2</vcpu>
    <type arch='x86_64' machine='pc-i440fx-utopic'>hvm</type>
    <boot dev='hd'/>
  <cpu mode='custom' match='exact'>
    <model fallback='allow'>SandyBridge</model>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/vmstorage/01/test01.img'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <alias name='usb0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x7'/>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <alias name='usb0'/>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0' multifunction='on'/>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <alias name='usb0'/>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x1'/>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <alias name='usb0'/>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x2'/>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    <controller type='ide' index='0'>
      <alias name='ide0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    <interface type='bridge'>
      <mac address='52:54:00:11:b2:c1'/>
      <source bridge='br0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target port='0'/>
      <alias name='serial0'/>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes' listen=''>
      <listen type='address' address=''/>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
  <seclabel type='dynamic' model='apparmor' relabel='yes'>

I now want to attach an USB stick. After some googleing I found some sources that basically all suggest the following approach:

  1. attach stick to host
  2. get vendor- and product-id

    root@host01:~# lsusb
    Bus 002 Device 004: ID 13fe:5100 Kingston Technology Company Inc. Flash Drive
    Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
    Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 001 Device 004: ID 0624:0249 Avocent Corp.
    Bus 001 Device 003: ID 0624:0248 Avocent Corp.
    Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  3. add new config-snippet to vm via virsh edit test01

      <!- ... ->
      <hostdev mode='subsystem' type='usb' managed='yes'>
          <vendor id='0x13fe'/>
          <product id='0x5100'/>
  4. restart vm

After that the vm should see the stick via lsusb, but nothing changes. If I try to attach the device to a second vm though, virsh start <othervm> fails with error: Requested operation is not valid: USB device 002:003 is in use by driver QEMU, domain test01 BUT I can still mount and access the stick on the host. I tried different sticks and different vm-operating systems (ubuntu and windows), no success.

Some instructions suggest to turn off apparmor, but a /etc/init.d/apparmor stop didn't change anything.

This is driving me nuts, since I don't get any error or log messages and I have no clue how to find out what's wrong. Any ideas on how to get the usb connected to the vm, or at least, how to analyse it further?

3 Answers 3


It's probably a problem with access rights. Your QEMU deamon is not allowed to access the USB devices. Try:

chown libvirt-qemu /dev/bus/usb/ -R

or whichever user your KVM is running as. This should do the trick.

  • This would only work temporarily until the next reboot; see my answer for a permanent solution.
    – user186340
    Feb 12, 2015 at 11:34
  • I had the same issue with ubuntu 16.04 and this didn't work for me. I found I need to modify the apparmor configuration as described in Ubuntu KVM passthrough wiki: help.ubuntu.com/community/KVM/…
    – Max
    Jul 15, 2017 at 20:01

To grant permanent access to the raw USB device nodes to the user the hypervisor runs as, you need to create an udev rule; the chown-based answer will only work until the next reboot.

In /lib/udev/rules.d, create a file like 51-usb_passthrough.rules :

SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ATTRS{busnum}=="2" ATTRS{devpath}=="1" GROUP="kvm"

Here I used physical bus and port numbers to target the device (as I prefer passing through the physical port no matter what device is plugged in rather than reconfiguring my VM each time I connect a new device), but of course you can use whatever attributes you want; the GROUP argument determines the group that will own the device node, this should be whatever user runs the virtual machines.

Run udevadm control --reload-rules to make the new rule effective immediately (you still need to disconnect/reconnect the USB devices) or simply reboot the host.

  • 1
    this didn't solve the problem for me
    – Natus Drew
    Jan 22, 2016 at 0:23

Easy solution: connect with

nc -U socket-file

to your QEMU monitor, where socket-file is the path to monitor. How to find: ps -FA | grep qemu. You will find there at the command line.

And run the command at the monitor:

device_add usb-host,id=<ANY string>,hostbus=<BUS>,hostport=<PORT>

this is pass-through by port number. You can pass through any device with any VID/PID. You can also pass-through particular devices using

device_add usb-host,id=<ANY string>,vendorid=0x0461,productid= 0x0010

and they can be plugged in to any port of your host.

Helpful commands also:

info usbhost
info usb
  • Note that instead of using netcat, you can likely use libvirt and virsh directly with something like virsh -c qemu:///system qemu-monitor-command --hmp test01 "device_add usb-host,...".
    – rabexc
    Nov 26, 2017 at 4:56

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