Debugging udev rules under Debian

I've been playing with the Finch, however today I was unhappy to discover that the robot stopped working again for non-root users. The Finch documentation helpfully links to this blog post on how to write a udev rule, which is the script I was using in the first place.

SUBSYSTEM=="usb", SYSFS{idVendor}=="2354", SYSFS{idProduct}=="1111", MODE="0660", GROUP="plugdev"

Time to figure out how to debug udev rules! The debian wiki hints at a tool called udevtest, which doesn't exist on my system or in aptitude. Turns out nowadays one should use udevadm test instead. Here we go: thanks to lsusb I know that the Finch is on bus 001, device 007.

# udevadm test /dev/bus/001/007

In the output around the rules file for the finch, there is this:

add_rule: unknown key 'SYSFS{idVendor}' in /etc/udev/rules.d/55-finch.rules:1
add_rule: invalid rule '/etc/udev/rules.d/55-finch.rules:1'

Looking for documentation on how to write udev rules, one would find the following guide, which indicates that ATTR should be used instead of SYSFS. Let's rewrite the rule:

SUBSYSTEM=="usb", ATTR{idVendor}=="2354", ATTR{idProduct}=="1111", MODE="0660", GROUP="plugdev"

The error doesn't show in the udevadm test output anymore, and unplugging/replugging the Finch makes it usable by non-root users again. Victory!

< Back to main >

Thanks for the post! I found you on google and this solved my udev problem I started having since I upgraded my Ubuntu install. #1. Posted by Cole Brodine on Fri 11 May 2012, 4:56

I'm glad it was helpful :) #2. Posted by jpichon (Website) on Fri 11 May 2012, 5:34

Thanks, just what I was looking for. Internet "recipes" can only get you so far. #3. Posted by Todd on Sat 25 May 2013, 14:03

Thanks! This was exactly the issue I was having~ and good pointer for the testing tool #4. Posted by Neil (Website) on Fri 01 Nov 2013, 3:52

Hello! This text is normally hidden with CSS. If you can see this, you'll also see two additional fields with no label on the form. Leave them as is, as those are aimed at catching form-filling spam bots. Thank you!

    Name: (or OpenID Sign in with OpenID)
      Email: (Not published)

          < Back to main | Up >