3 (on Debian /etc/udev/rules.d/50-udev.rules)
4 (on Ubuntu this should be in /etc/udev/rules.d/20-names.rules)
6 make sure there is the following:
8 KERNEL=="event[0-9]*", NAME="input/%k", GROUP="audio"
10 i.e. add GROUP="audio" to the lines, so that any user in the group "audio" can open the device.