Warum PyUSB / libusb erfordern root (sudo) Berechtigungen für Linux?

Question

Ich habe Herumspielen mit PyUSB in letzter Zeit, und fand, dass es schön auf Linux funktioniert (Ubuntu hat < a href = "http://www.libusb.org/" rel = "noreferrer"> libusb 0,1 und 1,0 sowie OpenUSB ) ... aber nur, wenn ich das Programm mit root-Rechten (mit sudo laufen, natürlich).

Kann mir jemand sagen, warum es erhöhte Rechte erfordert und, was noch wichtiger ist, wenn ich die Berechtigungen irgendwie ändern kann, um es für den normalen Benutzer-Accounts funktioniert?

Answer 1

libusb allows you to manipulate arbitrary USB devices in arbitrary ways. You could format an external USB harddisk, for example.

In general, all direct hardware access requires root privileges, although I guess that actually full root privileges are not required, you should be fine with just CAP_SYS_RAWIO.

Answer 2

You can change the permissions of your usb device node by creating a udev rule. e.g. I added the following line to a file in /etc/udev/rules.d/

SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", MODE="0664", GROUP="usbusers"

This sets the owner of the device node to root:usbusers rather than root:root

After adding myself to the usbusers group, I can access the device.

Answer 3

See the answer that I gave here:
How can I comunicate with this device using pyusb?

Namely:
Set up a udev rules file for the specific device that you want normal users to be able to access. This will define the vendor id, the product id and a group.
The vendor and product id's can be found using the lsusb command.

1. Create a udev rules file

ACTION=="add", SUBSYSTEMS=="usb", ATTRS{idVendor}=="171b", ATTRS{idProduct}=="2001", MODE="660", GROUP="plugdev"

Put this in a file called (for example) /lib/udev/rules.d/50-YourSoftwareName.rules (dig around in man udev for file naming rules)
NOTE: The old naming convention used /etc/udev/rules.d/filename.rules, that has changed.

2. add the user names to the plugdev group

adduser username plugdev

3. force the udev system to see your changes

sudo udevadm control --reload (that is minus minus reload)
sudo udevadm trigger

4. unplug and replug the device or reboot your machine

The end result should be that all members of the group plugdev will now be able to access the device.

EDIT: Note that on some systems the group plugdev may not be the group that you need. It can also be the group input in my experience, depending on what you are plugging in.