如何将FTDI串口转USB桥接设备挂载至Docker容器？（适配pyusb/libusb，避免privileged模式）

Hey there! Since you're new to Ubuntu, Docker, and Python, let's break this down step by step to get your FTDI USB device working in a Docker container without using privileged: true. The key issue here is that your FTDI device isn't showing up as a TTY (like Arduino does), so we need to mount the raw USB device node instead, and set up the right permissions for libusb to access it.

1. First: Confirm Your FTDI Device's Details on the Host #

You already started this, but let's formalize it to get all the info we need:

• Run lsusb to find your FTDI device. You should see a line like:

  Bus 003 Device 007: ID 0403:601c Future Technology Devices International, Ltd
  

  Note down the Bus number (003), Device number (007), Vendor ID (0x0403), and Product ID (0x601c).
• The raw USB device path on your host is /dev/bus/usb/<BUS_NUMBER>/<DEVICE_NUMBER> — in this example, that's /dev/bus/usb/003/007.

2. Option 1: Mount a Single FTDI Device to Your Container (Recommended) #

This is the safest approach since it only gives the container access to the specific device, not all system resources.

Update your docker-compose.yml #

Modify your service section to include:

services:
  your-service-name:
    # ... your existing config (image, volumes, command, etc.) ...
    devices:
      # Mount the raw USB device node from host to container (keep the same path)
      - "/dev/bus/usb/003/007:/dev/bus/usb/003/007"
    # Grant permission to access USB devices (189 is the major number for USB)
    device_cgroup_rules:
      - 'c 189:* rwm'
    # Run the container with your host user's UID/GID to avoid permission issues
    user: "${UID}:${GID}"

• Quick breakdown of each setting:
  • devices mounts the exact USB device node into the container, so libusb can locate it the same way it does on the host.
  • device_cgroup_rules: 'c 189:* rwm' gives the container read/write/modify access to all USB devices (you can narrow this to your specific device if needed, but this is simpler for starters).
  • user: "${UID}:${GID}" ensures the container user has the same permissions as your host user. To get your UID/GID, run id -u and id -g on the host.

Install Dependencies in the Container #

Make sure your Dockerfile (or container setup) installs the required libraries for pyusb and libusb. If you're using a Debian/Ubuntu-based image:

RUN apt-get update && apt-get install -y \
    libusb-1.0-0-dev \
    python3-pip
RUN pip3 install pyusb

Test the Python Script in the Container #

Run your script again. If you still hit the NoBackendError, try explicitly specifying the libusb backend in your code (this ensures pyusb uses the correct library in the container):

import usb.core
import usb.util
import usb.backend.libusb1

# Point to the libusb shared library in the container
backend = usb.backend.libusb1.get_backend(find_library=lambda x: "/usr/lib/x86_64-linux-gnu/libusb-1.0.so.0")

# Find the device using the specified backend
device = usb.core.find(idVendor=0x0403, idProduct=0x601c, backend=backend)

if device is None:
    raise ValueError('Device not found')
else:
    print(device)

3. Option 2: Mount All USB Devices to the Container (Less Secure, But Convenient) #

If you want the container to access all USB devices on the host (not just the FTDI one), use these settings in docker-compose.yml:

services:
  your-service-name:
    # ... existing config ...
    volumes:
      - "/dev/bus/usb:/dev/bus/usb"
    device_cgroup_rules:
      - 'c 189:* rwm'
    user: "${UID}:${GID}"

This mounts the entire USB bus directory into the container, so any USB device connected to the host will be visible inside.

4. Troubleshooting Tips #

• Device not found in container?
  • Double-check the bus/device numbers — they can change if you unplug/replug the device. Run lsusb again to confirm.
  • Make sure your host user is in the plugdev or dialout group. Run sudo usermod -aG plugdev $USER and log out/in to apply.
  • In the container, run ls /dev/bus/usb/003/007 to confirm the device node exists. If not, check your devices or volumes mount in docker-compose.
• Permission errors?
  • Verify the device_cgroup_rules is set correctly.
  • Ensure the container user has the same UID/GID as your host user (the user field in docker-compose helps with this).

内容的提问来源于stack exchange，提问作者ThunderBolt84