qubes-doc/StickMounting.md

---
layout: doc
title: StickMounting
permalink: /doc/StickMounting/
redirect_from: /wiki/StickMounting/
---

How to Mount USB Sticks to AppVMs
=================================

(**Note:** In the present context, the term "USB stick" denotes any [USB mass storage device](https://en.wikipedia.org/wiki/USB_mass_storage_device_class). In addition to smaller flash memory sticks, this includes things like USB external hard drives.)

Qubes supports the ability to attach a USB stick (or just one or more of its partitions) to any AppVM easily, no matter which VM actually handles the USB controller. (The USB controller may be assigned on the **Devices** tab of an AppVM's settings page in Qubes VM Manager or by using the [qvm-pci command](/doc/AssigningDevices/).)

As of Qubes R2 Beta 3, USB stick mounting has been integrated into the Qubes VM Manger GUI. Simply insert your USB stick, right-click the desired AppVM in the Qubes VM Manager list, click **Attach/detach block devices**, and select your desired action and device. This, however, only works for the whole device. If you would like to attach individual partitions you must use the command-line tool (shown below). The reason for this is that when attaching a single partition, it used to be that Nautilus file manager would not see it and automatically mount it (see [this ticket](https://github.com/QubesOS/qubes-issues/issues/623)). This problem, however, seems to be resolved (see [this issue comment](https://github.com/QubesOS/qubes-issues/issues/1072#issuecomment-124270051)). If for some reason it does not show up in nautilus for you and you still need to attach just a single partition to a device, you will need to mount it manually; the device will show up as /dev/xvdi (or /dev/xvdj if there is already one device attached--/dev/xvdk and so on).

The command-line tool you may use to mount whole USB sticks or their partitions is `qvm-block`. This tool can be used to assign a USB stick to an AppVM as follows:

1.  Insert your USB stick.

1.  In a dom0 console (running as normal user), list all available block devices:

        qvm-block -l

    This will list all available block devices connected to any USB controller
    in your system, no matter in which VM hosts the controller. The name of the
    VM hosting the USB controller is displayed before the colon in the device
    name. The string after the colon is the name of the device used within the
    VM.

    **Note:** If your device is not listed here, you may refresh the list by calling (from the VM to which device is connected):

        sudo udevadm trigger --action=change


1.  Assuming our USB stick is sdb, we attach the device to an AppVM like so:

       qvm-block -a personal dom0:sdb
   
    This will attach the device as "/dev/xvdi", if not already taken by another attached device, in the AppVM. You may also mount one partition at a time by using the same command with the partition number after sdb.

    **Warning: when working with single partitions, it is possible to assign the same partition to multiple VMs.** For example, you could attach sdb1 to VM1 and then sdb to VM2. It is up to the user not to make this mistake. Xen block device framework currently does not provide an easy way around this. Point 2 of [this ticket comment](https://github.com/QubesOS/qubes-issues/issues/1072#issuecomment-124119309) gives details on this.

1.  The USB stick is now attached to the AppVM. If using a default AppVM, you may open Nautilus file manager in the AppVM, and your stick should be visible in the **Devices** panel on the left.

1.  When you finish using your USB stick, click the eject button or right-click and select **Unmount**.

1.  In a dom0 console, detach the stick:

        qvm-block -d <device> <vmname>

1.  You may now remove the device.

**Warning: Do not remove the device before detatching it from the VM!** Otherwise you
will not be able to attach it anywhere later. See [this
ticket](https://github.com/QubesOS/qubes-issues/issues/1082) for details.


What if I removed the device before detaching it from the VM?
------------------------------------------------------------

Currently (until [this
ticket](https://github.com/QubesOS/qubes-issues/issues/1082) got implemented),
if you remove the device before detaching it from the VM, Qubes (more precisely
- libvirtd) will think that the device is still attached to the VM and will not
allow attaching further devices under the same name. The easiest way to recover
from such situation is to reboot the VM to which device was attached. But if
this isn't an option, you can manually recover from the situation by following
this steps:

1. Physically connect the device back. You can use any device as long as it
   will be detected under the same name (for example `sdb`).
2. Attach the device manually to the same VM using `xl block-attach` command.
   It is important to use the same "frontend" device name (by default `xvdi`) -
   you can get it from `qvm-block` listing:

       [user@dom0 ~]$ qvm-block
       sys-usb:sda DataTraveler_2.0 () 246 MiB (attached to 'testvm' as 'xvdi')
       [user@dom0 ~]$ xl block-attach testvm phy:/dev/sda backend=sys-usb xvdi

   In above example all `xl block-attach` parameters can be deducted from
   `qvm-block` output. In order:

   * `testvm` - name of target VM to which device was attached - listed in brackets by `qvm-block` command
   * `phy:/dev/sda` - physical path at which device appears in source VM (just after source VM name in `qvm-block` output) 
   * `backend=sys-usb` - name of source VM, can be omitted in case of dom0
   * `xvdi` - "frontend" device name (listed at the end of line in `qvm-block` output

3. Now properly detach the device, either using Qubes Manager, or `qvm-block -d` command.