Git-Mirrors/qubes-doc
1
0
Fork 0
mirror of https://github.com/QubesOS/qubes-doc.git synced 2025-05-02 06:46:11 -04:00
Code Issues Projects Releases Packages Wiki Activity

Added rearranged documentation on devices in R4.0

Browse source
This commit is contained in:
GammaSQ 2019-01-05 10:30:04 +01:00
parent c551a862aa
commit e2258ac74c
No known key found for this signature in database
GPG key ID: D552FD2F98647C64
6 changed files with 841 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

164
common-tasks/block-devices.md Normal file
View file

@ -0,0 +1,164 @@
---
layout: doc
title: Block or Storage Devices in Qubes R4.0
permalink: /doc/block-devices/
redirect_from:
- /doc/block-devices-in-qubes-R4.0/
---
Block or Storage Devices in Qubes R4.0
======================================
If you don't know what a "block device" is, just think of it as a fancy way to say "something that stores data".
#Using The GUI to Attach a Drive
(**Note:** In the present context, the term "USB drive" denotes any [USB mass storage device][mass-storage].
In addition to smaller flash memory sticks, this includes things like USB external hard drives.)
Qubes OS supports the ability to attach a USB drive (or just its partitions) to any qube easily, no matter which qube handles the USB controller.
Attaching USB drives is integrated into the Devices Widget: ![device manager icon]
Simply insert your USB drive and click on the widget.
You will see multiple entries for your USB drive; typically, `sys-usb:sda`, `sys-usb:sda1`, and `sys-usb:2-1` for example.
Entries starting with a number (e.g. here `2-1`) are the [whole usb-device][USB]. Entries without a number (e.g. here `sda`) are the whole block-device. Other entries are partitions of that block-device (e.r. here `sda1`).
The simplest option is to attach the entire block drive.
In our example, this is `sys-usb:sda`, so hover over it.
This will pop up a submenu showing running VMs to which the USB drive can be connected.
Click on one and your USB drive will be attached!
**Note:** attaching individual partitions (e.g. `sys-usb:sda1`) can be slightly more secure because it doesn't force the target AppVM to parse the partition table.
However, it often means the AppVM won't detect the new partition and you will need to manually mount it inside the AppVM.
See below for more detailed steps.
#Block Devices in VMs
If not specified otherwise, block devices will show up as `/dev/xvdi*` in a linux VM, where `*` may be the partition-number. If a block device isn't automatically mounted after attaching, open a terminal in the VM and execute:
cd ~
mkdir mnt
sudo mount /dev/xvdi2 mnt
where `xvdi2` needs to be replaced with the partition you want to mount.
This will make your drive content accessible under `~/mnt`.
Beware that when you attach a whole block device, partitions can be identified by their trailing integer (i.e. `/dev/xvdi2` for the second partition, `/dev/xvdi` for the whole device), whereas if you attach a single parition, the partition has *no trailing integer*. <!--TODO: really? Didn't have a drive to test this quickly.-->
If several different block-devices are attached to a single VM, the last letter of the device node name is advanced through the alphabet, so after `xvdi` the next device will be named `xvdj`, the next `xvdk`, and so on.
To specify this device node name, you can pass `--option frontend-dev=[custom-node-name]` to `qvm-block attach`.
#Commandline Tool Guide
The command-line tool you may use to mount whole USB drives or their partitions is `qvm-block`, a shortcut for `qvm-device block`.
`qvm-block` only sees device-nodes and may not use names you expect! So make sure to have the drive available in the sourceVM before listing available block devices (step 1.) to find out it's its ID.
In case of a USB-drive, make sure it's attached to your computer. If you don't see anything that looks like your drive, run `sudo udevadm trigger --action=change` in your USB-qube (typically `sys-usb`)
1. In a dom0 console (running as a normal user), list all available block devices:
qvm-block
This will list all available block devices in your system across all VMs, no matter whether hosted by a USB controller or `losetup`.
The name of the qube hosting the block device is displayed before the colon in the device ID.
The string after the colon is the ID of the device used within the qube, like so:
sourceVM:sdb Cruzer () 4GiB
sourceVM:sdb1 Disk () 2GiB
2. Assuming your block device is attached to `sys-usb` and its device node is `sdb`, we attach the device to a qube with the name `work` like so:
qvm-block attach work sys-usb:sdb
This will attach the device to the qube as `/dev/xvdi` if that name is not already taken by another attached device, or `/dev/xvdj`, etc.
You may also mount one partition at a time by using the same command with the partition number, e.g. `sdb1`.
3. The block device is now attached to the qube.
If using a default qube, you may open the Nautilus file manager in the qube, and your drive should be visible in the **Devices** panel on the left.
If you've attached a single partition (e.g. `sdb2` instead of `sdb` in our example), you may need to manually mount before it becomes visible:
cd ~
mkdir mnt
sudo mount /dev/xvdi mnt
4. When you finish using the block device, click the eject button or right-click and select **Unmount**.
If you've manually mounted a single partition in the above step, use:
sudo umount mnt
5. In a dom0 console, detach the device
qvm-block detach work sys-usb:sdb
6. You may now remove the device or attach it to another qube.
<!--TODO: what happens if USB-device removed before detaching? How about attaching a blockdevice to two qubes?-->
#Attaching a File
To attach a file as block device to another qube, first turn it into a loopback device inside the sourceVM.
1. In the linux sourceVM run
sudo losetup /dev/loop0 /path/to/file
(increase the trailing integer if `loop0` is already in use or use other name. This is just a generic device-id.)
2. If you want to use the GUI, you're done. Click the Device Manager ![device manager icon] and select the `loop0`-device to attach it to another qube.
If you rather use the commandline, continue:
In dom0, run `qvm-block` to display known block devices. The newly created loop device should show up:
~]$ qvm-block
BACKEND:DEVID DESCRIPTION USED BY
sourceVM:loop0 /path/to/file
3. Attach the `loop0`-device using qvm-block as usual:
qvm-block a targetVM sourceVM:loop0
4. After detaching, destroy the loop-device inside the sourceVM as follows:
sudo losetup -d /dev/loop0
#Additional Attach Options
Attaching a block device through the commandline offers additional customisation options, specifiable via the `--option`/`-o` option. (Yes, confusing wording, there's an [issue for that](https://github.com/QubesOS/qubes-issues/issues/4530).)
##frontend-dev
This option allows you to specify the name of the device node made available in the targetVM. This defaults to `xvdi` or, if already occupied, the first available device node name in alphabetical order. (The next one tried will be `xvdj`, then `xvdk`, and so on ...)
usage example:
qvm-block a work sys-usb:sda1 -o frontend-dev=xvdz
This command will attach the partition `sda1` to `work` as `/dev/xvdz`.
##read-only
Attach device in read-only mode. Protects the block device in case you don't trust the targetVM.
If the device is a read-only device, this option is forced true.
usage example:
qvm-block a work sys-usb:sda1 -o read-only=true
There exists a shortcut to set read-only `true`, `--ro`:
qvm-block a work sys-usb:sda1 --ro
The two commands are equivalent.
##devtype
Usually, a block device is attached as disk. In case you need to attach a block device as cdrom, this option allows that.
usage example:
qvm-block a work sys-usb:sda1 -o devtype=cdrom
This option accepts `cdrom` and `disk`, default is `disk`.
[mass-storage]: https://en.wikipedia.org/wiki/USB_mass_storage_device_class
[device manager icon]:https://raw.githubusercontent.com/hrdwrrsk/adwaita-xfce-icon-theme/master/Adwaita-Xfce/22x22/devices/media-removable.png <!--TODO: find actual icon used in qubes!-->
[USB]:/dock/usb-devices-in-qubes-R4.0/

118
common-tasks/device-handling.md Normal file
View file

@ -0,0 +1,118 @@
---
layout: doc
title: Device Handling in Qubes R4.0
permalink: /doc/device-handling/
redirect_from:
- /doc/device-handling-in-qubes-R4.0/
---
Device Handling in Qubes R4.0
=============================
**Note:** This is an overview for device-handling in QubesOS. For specific devices ([block], [USB] and [PCI] devices), please visit the respective page.
**Important security warning:** Device handling comes with many security implications! Please make sure you carefully read and understood the **[security considerations]**!
----------------------
The interface to deal with devices of all sorts was unified in Q4.0 with the `qvm-device` command and the Qubes Devices Widget. In Q3.X, the Qubes VM Manager dealt with attachment as well. This functionality was moved to the Qubes Device Widget, the tool tray icon with a yellow square located in the top right of your screen by default.
There are currently four categories of devices Qubes understands:
- Microphones
- Block devices
- USB devices
- PCI devices
Microphones, block devices and USB devices can be attached with the GUI-tool. PCI devices require the command line tool.
#Security Considerations
#General Qubes Device Widget Behavior And Handling
When clicking on the tray icon (looking similar to this: ![SD card and thumbdrive][device manager icon] several device-classes seperated by lines are displayed as tooltip. Block devices are displayed on top, microphones one below and USB-devices at the bottom.
On most laptops, integrated hardware such as cameras and fingerprint-readers are implemented as USB-devices and can be found here.
##Attaching Using The Widget
Click the tray icon. Hover on a device you want to attach to a VM. A list of running VMs (except dom0) appears. Click on one and your device will be attached!
##Detaching Using The Widget
To detach a device, click the Qubes Devices Widget icon again. Attached devices are displayed in bold. Hover the one you want to detach. A list of VMs appears, one showing the eject symbol: ![eject icon]
##Attaching a Device to Several VMs
<!--TODO: This seems like a very bad idea, but it's possible? When would I want to do that? What are the security-implications?-->
#General `qvm-device` Commandline Tool Behavior
All devices, including PCI-devices, may be attached from the commandline using the `qvm-device`-tools.
##Device Classes
`qvm-device` expects DEVICE_CLASS as first argument. DEVICE_CLASS can be one of
- `pci`
- `usb`
- `block`
- `mic`
##Actions
`qvm-device` supports three actions:
- `list` (ls, l) - list all devices of DEVICE_CLASS
- `attach` (at, a) - attach a specific device of DEVICE_CLASS
- `detach` (dt, d) - detach a specific device of DEVICE_CLASS
##Global Options
These three options are allways available:
- `--help`, `-h` - show help message and exit
- `--verbose`, `-v` - increase verbosity
- `--quiet`, `-q` - decrease verbosity
A full command consits of one DEVICE_CLASS and one action. If no action is given, list is implied. DEVICE_CLASS however is required.
**SYNOPSIS**:
`qvm-device DEVICE_CLASS {action} [action-specific arguments] [options]`
##Actions
Actions are applicable to every DEVICE_CLASS and expose some additional options.
###Listing Devices
The `list` action lists known devices in the system. `list` accepts VM-names to narrow down listed devices. <!--TODO: are specified VMs searched for AVAILABLE or also attached devices? Would after `qvm-usb a work sys-usb:1-1` the command `qvm-usb l work` yield any result?-->
`list` accepts two options:
- `--all` - equivalent to specifying every VM name after `list`. No VM-name implies `--all`.
- `--exclude` - exclude VMs from `--all`. Requires `--all`.
**SYNOPSIS**
`qvm-device DEVICE_CLASS {list|ls|l} [--all [--exclude VM [VM [...]]] | VM [VM [...]]]`
###Attaching Devices
The `attach` action assigns an exposed device to a VM. This makes the device available in the VM it's attached to. Required argument are targetVM and sourceVM:deviceID. (sourceVM:deviceID can be determined from `list` output)
`attach` accepts two options:
- `--persistent` - attach device on targetVM-boot. If the device is unavailable (physically missing or sourceVM not started), booting the targetVM fails.
- `--option`, `-o` - set additional options specific to DEVICE_CLASS.
**SYNOPSIS**
`qvm-device DEVICE_CLASS {attach|at|a} targetVM sourceVM:deviceID [options]`
###Detaching Devices
The `detach` action removes an assigned device from a targetVM. It won't be available afterwards anymore. Though it tries to do so gracefully, beware that data-connections might be broken unexpectedly, so close any transaction before deatching a device!
`detach` accepts no options.
**SYNOPSIS**
`qvm-device DEVICE_CLASS {detach|dt|d} targetVM sourceVM:deviceID`
<!--TODO: Is sourceVM:deviceID still required? -->
[block]:/doc/block-devices-in-qubes-R4.0/
[USB]:/dock/usb-devices-in-qubes-R4.0/
[PCI]:/doc/pci-devices-in-qubes-R4.0/
[security considerations]: /doc/device-considerations/
[device manager icon]: https://raw.githubusercontent.com/hrdwrrsk/adwaita-xfce-icon-theme/master/Adwaita-Xfce/22x22/devices/media-removable.png <!--TODO: find actual icon used in qubes!-->
[eject icon]: https://raw.githubusercontent.com/hrdwrrsk/adwaita-xfce-icon-theme/master/Adwaita-Xfce/22x22/actions/media-eject.png

146
common-tasks/pci-devices.md Normal file
View file

@ -0,0 +1,146 @@
---
layout: doc
title: PCI Devices in Qubes R4.0
permalink: /doc/pci-devices/
redirect_from:
- /doc/pci-devices-in-qubes-R4.0/
---
PCI Devices in Qubes R4.0
======================================
(In case you were looking for the [R3.2 documentation](/doc/assigning-devices/).)
**Warning:** Only dom0 exposes PCI devices. Some of them are strictly required in dom0! (e.g. host bridge)
You may end up with an unusable system by attaching the wrong PCI device to a VM.
**Security warning:** PCI passthrough should be safe by default, but none-default options may be required. Please make sure you carefully read and understood the **[security considerations]** before deviating from default behavior!
Unlike other devices ([USB], [block], mic), PCI devices need to be attached on VM-bootup. Similar to how you can't attach a new soundcard after your computer booted (and expect it to work properly), attaching PCI devices to already booted VMs isn't possible in any meaningful way.
The Qubes installer attaches all network class controllers to `sys-net` and all USB controllers to `sys-usb` by default, if you chose to create the network and USB qube during install.
While this covers most use cases, there are some occasions when you may want to manually attach one NIC to `sys-net` and another to a custom NetVM, or have some other type of PCI controller you want to manually attach.
Note that one can only attach full PCI or PCI Express devices by default.
This limit is imposed by the PC and VT-d architectures.
This means if a PCI device has multiple functions, all instances of it need to be attached to the same qube unless you have disabled the strict requirement with the `no-strict-reset` option during attachment.
In the steps below, you can tell if this is needed if you see the BDF for the same device listed multiple times with only the number after the "." changing.
While PCI device can only be used by one powered on VM at a time, it *is* possible to *assign* the same device to more than one VM at a time.
This means that you can use the device in one VM, shut that VM down, start up a different VM (to which the same device is now attached), then use the device in that VM.
This can be useful if, for example, you have only one USB controller, but you have multiple security domains which all require the use of different USB devices.
#Attaching Devices Using the GUI
The qube settings for a VM offers the "Devices"-tab. There you can attach PCI-devices to a qube.
1. To reach the settings of any qube either
- Press Alt+F3 to open the application finder, type in the VM name, select the "![appmenu]\[VM-name\]: Qube Settings" menu entry and press enter or click "Launch"!
- Select the VM in Qube Manager and click the settings-button or right-click the VM and select `Qube settings`.
- Click the Domain Manager ![device manager icon], hover the VM you want to assing a device to and select "settings" in the additional menu. (only running VMs!)
2. Select the "Devices" tab on the top bar.
3. Select a device you want to attach to the qube and click the single arrow right! (`>`)
4. You're done. If everything worked out, once the qube boots (or reboots if it's running) it will start with the pci device attached.
5. In case it doesn't work out, first try disabeling memory-balancing in the settings ("Advanced" tab). If that doesn't help, read on to learn how to disable the strict reset requirement!
#`qvm-pci` Usage
The `qvm-pci` tool allows PCI attachment and detachment. It's a shortcut for [`qvm-device pci`][qvm-device].
To figure out what device to attach, first list the available PCI devices by running (as user) in dom0:
qvm-pci
This will show you the `backend:BDF` (Bus_Device.Function) address of each PCI device.
It will look something like `dom0:00_1a.0`.
Once you've found the address of the device you want to attach, then attach it like this:
qvm-pci attach targetVM sourceVM:[BDF] --persistent
Since PCI devices have to be attached on bootup, attaching has to happen with the `--persistant` option.
For example, if `00_1a.0` is the BDF of the device you want to attach to the "work" domain, you would do this:
qvm-pci attach work dom0:00_1a.0 --persistent
#Possible Issues
##DMA Buffer Size
VMs with assigned PCI devices in Qubes have allocated a small buffer for DMA operations (called swiotlb).
By default it is 2MB, but some devices need a larger buffer.
To change this allocation, edit VM's kernel parameters (this is expressed in 512B chunks):
# qvm-prefs netvm |grep kernelopts
kernelopts : iommu=soft swiotlb=2048 (default)
# qvm-prefs -s netvm kernelopts "iommu=soft swiotlb=8192"
This is [known to be needed][ml1] for the Realtek RTL8111DL Gigabit Ethernet Controller.
##PCI Passthrough Issues
Sometimes the PCI arbitrator is too strict.
There is a way to enable permissive mode for it.
See also: [this thread][ml2] and the Xen wiki's [PCI passthrough] page.
At other times, you may instead need to disable the FLR requirement on a device.
Both can be acchieved during attachment with `qvm-pci` as described below.
#Additional Attach Options
Attaching a PCI device through the commandline offers additional options, specifiable via the `--option`/`-o` option. (Yes, confusing wording, there's an [issue for that](https://github.com/QubesOS/qubes-issues/issues/4530).)
`qvm-pci` exposes two additional options. Both are intended to fix device or driver specific issues, but both come with [heavy security implications][security considerations]! **Make sure you understand them before continuing!**
##no-strict-reset
Do not require PCI device to be reset before attaching it to another VM. This may leak usage data even without malicious intent!
usage example:
qvm-pci a work dom0:00_1a.0 --persistent -o no-strict-reset=true
##permissive
Allow write access to full PCI config space instead of whitlisted registers. This increases attack surface and possibility of [side channel attacks].
usage example:
qvm-pci a work dom0:00_1a.0 --persistent -o no-strict-reset=true
#Bringing PCI device back to dom0
By default, when a device is detached from a VM (or when a VM with an attached PCI device is shut down), the device is *not* automatically attached back to dom0.
This is an intended feature.
A device which was previously assigned to a VM less trusted than dom0 (which, in Qubes, is *all* of them) could attack dom0 if it were automatically reassigned there.
In order to re-enable the device in dom0, either:
* Reboot the physical machine. (Best practice)
or
* Go to the sysfs (`/sys/bus/pci`), find the right device, detach it from the pciback driver, and attach it back to the original driver.
Replace `<BDF>` with your full device, for example `0000:00:1c.2`:
echo <BDF> > /sys/bus/pci/drivers/pciback/unbind
MODALIAS=`cat /sys/bus/pci/devices/<BDF>/modalias`
MOD=`modprobe -R $MODALIAS | head -n 1`
echo <BDF> > /sys/bus/pci/drivers/$MOD/bind
It is **strongly discouraged to reattach PCI devices to dom0**, especially if they don't support resetting!
<!--TODO: Is this still needed?-->
[security considerations]: /doc/device-considerations/#pci-security
[block]:/doc/block-devices-in-qubes-R4.0/
[USB]:/dock/usb-devices-in-qubes-R4.0/
[appmenu]: https://raw.githubusercontent.com/QubesOS/qubes-artwork/master/icons/32x32/apps/qubes-appmenu-select.png
[domain manager icon]: https://raw.githubusercontent.com/QubesOS/qubes-artwork/master/icons/32x32/apps/qubes-logo-icon.png
[qvm-device]: /doc/device-handling-in-qubes-R4.0/#general-qubes-device-widget-behavior-and-handling
[side channel attacks]: https://en.wikipedia.org/wiki/Side-channel_attack
[ml1]: https://groups.google.com/group/qubes-devel/browse_thread/thread/631c4a3a9d1186e3
[ml2]: https://groups.google.com/forum/#!topic/qubes-users/Fs94QAc3vQI
[PCI passthrough]: https://wiki.xen.org/wiki/Xen_PCI_Passthrough

142
common-tasks/usb-devices.md Normal file
View file

@ -0,0 +1,142 @@
---
layout: doc
title: USB Devices in Qubes R4.0
permalink: /doc/usb-devices/
redirect_from:
- /doc/usb-devices-in-qubes-R4.0/
---
USB Devices in Qubes R4.0
==========================
(In case you were looking for the [R3.2 documentation](/doc/usb/).)
**Important security warning:** USB passthrough comes with many security implications! Please make sure you carefully read and understood the **[security considerations]**! Especially, whenever possible, attach a [block device] instead!
Examples for valid cases for USB-passthrough:
- [microcontroller programming]
- using [extarnal audio devices]
- [optical drives] for recording
(If you are thinking to use a two-factor-authentification device, [there is an app for that][qubes u2f proxy]. But it has some [issues][4661].)
#Attaching And Detaching a USB Device
##With Qubes Device Manager
Click the device-manager-icon: ![device manager icon]
A list of available devices appears. USB-devices have a USB-icon to their right. <!--TODO: Where is that icon????-->
Hover on one device to display a list of VMs you may attach it to.
Click one of those. The USB device will be attached to it. You're done.
After you finished using the USB-device, you can detach it the same way by clicking on the Devices Widget.
You will see an entry in bold for your device such as **`sys-usb:2-5 - 058f_USB_2.0_Camera`**.
Hover on the attached device to display a list of running VMs.
The one to which your device is connected will have an eject button ![eject icon] next to it.
Click that and your device will be detached.
##With The Command Line Tool
In dom0, you can use `qvm-usb` from the commandline to attach and detach devices.
Listing available USB devices:
[user@dom0 ~]$ qvm-usb
sys-usb:2-4 04ca:300d 04ca_300d
sys-usb:2-5 058f:3822 058f_USB_2.0_Camera
sys-usb:2-1 03f0:0641 PixArt_HP_X1200_USB_Optical_Mouse
Attaching selected USB device:
[user@dom0 ~]$ qvm-usb attach work sys-usb:2-5
[user@dom0 ~]$ qvm-usb
work:2-1 058f:3822 058f_USB_2.0_Camera
sys-usb:2-4 04ca:300d 04ca_300d
sys-usb:2-5 058f:3822 058f_USB_2.0_Camera (attached to work)
sys-usb:2-1 03f0:0641 PixArt_HP_X1200_USB_Optical_Mouse
Now, you can use your USB device (camera in this case) in the `work` qube.
If you see the error `ERROR: qubes-usb-proxy not installed in the VM` instead, please refer to the [Installation Section].
When you finish, detach the device.
[user@dom0 ~]$ qvm-usb detach work sys-usb:2-5
[user@dom0 ~]$ qvm-usb
sys-usb:2-4 04ca:300d 04ca_300d
sys-usb:2-5 058f:3822 058f_USB_2.0_Camera
sys-usb:2-1 03f0:0641 PixArt_HP_X1200_USB_Optical_Mouse
#Maintainence And Customisation
##Creating And Using a USB qube
If you've selected to install a usb-qube during system installation, everything is already set up for you in `sys-usb`. If you've later decided to create a usb-qube, plese follow [this guide][USB-qube howto].
##Installation Of `qubes-usb-proxy`
To use this feature, the[`qubes-usb-proxy`][qubes-usb-proxy] package needs to be installed in the templates used for the USB qube and qubes you want to connect USB devices to.
This section exists for reference or in case something broke and you need to reinstall `qubes-usb-proxy`. Under normal conditions, `qubes-usb-proxy` should already be installed and good to go.
If you receive this error: `ERROR: qubes-usb-proxy not installed in the VM`, you can install the `qubes-usb-proxy` with the package manager in the VM you want to attach the USB device to.
Note: you cannot pass through devices from dom0 (in other words: a [USB qube][USB-qube howto] is required).
`qubes-usb-proxy` should be installed by default in the template VM.
- Fedora: `sudo dnf install qubes-usb-proxy`
- Debian/Ubuntu: `sudo apt-get install qubes-usb-proxy`
##Using USB Keyboards And Other Input Devices
**Warning:** especially keyboards need to be accepted by default when using them to login! Please make sure you carefully read and understood the **[security considerations]** before continuing!
Mouse and keyboard setup are part of [setting up a USB-qube][keyboard setup].
##Finding the right USB controller
<!--TODO: This looks super old. Somebody please have a look! -->
Some USB devices are not compatible with the USB pass-through method Qubes employs.
In situations like these, you can try to pass through the entire USB controller to a qube as PCI device.
However, with this approach one cannot attach single USB devices but has to attach the whole USB controller with whatever USB devices are connected to it.
If you have multiple USB controllers, you must first figure out which PCI device is the right controller.
First, find out which USB bus the device is connected to (note that these steps need to be run from a terminal inside your USB qube):
lsusb
For example, I want to attach a broadband modem to the NetVM.
In the output of `lsusb` it may be listed as something like:
Bus 003 Device 003: ID 413c:818d Dell Computer Corp.
(In this case, the device isn't fully identified)
The device is connected to USB bus \#3.
Check which other devices are connected to the same bus, since *all* of them will be attach to the same VM.
To find the right controller, follow the usb bus:
readlink /sys/bus/usb/devices/usb3
This should output something like:
../../../devices/pci-0/pci0000:00/0000:00:1a.0/usb3
Now you see the BDF address in the path (right before final `usb3`).
Strip the leading `0000:` and pass the rest to the [`qvm-pci` tool][qvm-pci] to attach the controller to the targetVM.
[block device]: /doc/block-devices-in-qubes-R4.0/
[security considerations]: /doc/device-considerations/#usb-security
[usb-challenges]: https://blog.invisiblethings.org/2011/05/31/usb-security-challenges.html
[microcontroller programming]: https://www.arduino.cc/en/Main/Howto
[extarnal audio devices]: /doc/external-audio/
[optical drives]: /doc/recording-optical-discs/
[qubes u2f proxy]: https://www.qubes-os.org/news/2018/09/11/qubes-u2f-proxy/
[4661]: https://github.com/QubesOS/qubes-issues/issues/4661
[device manager icon]:https://raw.githubusercontent.com/hrdwrrsk/adwaita-xfce-icon-theme/master/Adwaita-Xfce/22x22/devices/media-removable.png <!--TODO: find actual icon used in qubes!-->
[eject icon]:https://raw.githubusercontent.com/hrdwrrsk/adwaita-xfce-icon-theme/master/Adwaita-Xfce/22x22/actions/media-eject.png
[Installation Section]:#installation-of-qubes-usb-proxy
[USB-qube howto]: /doc/usb-qube-howto/
[keyboard setup]: /doc/usb-qube-howto/#enable-a-usb-keyboard-for-login
[qvm-pci]: /doc/pci-devices-in-qubes-R4.0/