Thank you @nedkonz for sharing your experience, and welcome to the forum! Sorry to hear that you ran into an issue, but great that you were able to fix it! I am a little confused as to why it worked though. The original udev rule grants Joulescope read/write access to everyone, so the GROUP specification shouldn’t matter.
If you have a moment, I would be interested in knowing the resulting permissions on your computer. You need to issue two commands:
$ lsusb -d 16d0:0e88
$ ls -al /dev/bus/usb/{bus}/{device}
Replacing {bus} and {device} with the values returned by lsusb. On my system, I see:
$ lsusb -d 16d0:0e88
Bus 002 Device 021: ID 16d0:0e88 MCS
$ ls -al /dev/bus/usb/002/021
crw-rw-rw- 1 root root 189, 148 Jun 26 19:07 /dev/bus/usb/002/021
root is the owner with read/write permissions, root is the group with read/write permissions and everyone has read/write permissions. I would expect your rules to generate the same permissions, except the group should be plugdev. However, the behavior you described indicates 0660 permissions were applied instead.
I agree that it’s better security practices to grant 0660 permissions, assign a GROUP and ensure that your account is part of that group, but it also means that I would also have to ask people to do:
sudo usermod -a -G plugdev `whoami`
and then log out and back in again. I will add , GROUP="plugdev" to the rules regardless and add comments for how to add users to the plugdev group. Here is what I added:
# This file grants everyone read/write access. If you want to restrict access,
# you should modify MODE to "0660". You can then grant access to specific user
# accounts by adding them to the plugdev group. To grant yourself permission:
#
# sudo usermod -a -G plugdev `whoami`
#
# You will have to log out and then back in for the group change to take effect.
# To grant permission to a specific {user}:
#
# sudo usermod -a -G plugdev {user}
#
# replacing {user} with the actual username.
Thanks again, and I hope that you enjoy using your Joulescope!