I noticed on my existing tumbleweed desktop, when I login a setfacl appears to be setting permissions on /dev/i2c-1 and they are reassigned to sddm on logout. % getfacl /dev/i2c-1 getfacl: Removing leading '/' from absolute path names # file: dev/i2c-1 # owner: root # group: root user::rw- user:michael:rw- group::--- mask::rw- other::--- This appears to happen for all users. But on a recently installed tumbleweed I don't see this behavior - no users have access to the i2c devices, no ACL's are assign on login. There is no i2c related group on either the old or new machine. Both machines are on the latest tumbleweed, both run Nvidia's driver. So I would expect the same behaviour on both. I do see that the nvidia devices have ACL's set on login (so perhaps this is X11 or nvidia related): getfacl /dev/nvidia0 getfacl: Removing leading '/' from absolute path names # file: dev/nvidia0 # owner: root # group: video user::rw- user:michael:rw- group::rw- mask::rw- other::--- It's possible I setup something years ago and have forgotten about it. I think I have used i2c in the past for sensors. More recently I've started using it with ddcutil and vdu_controls (which I wrote) - I was puzzled that they work with no permission changes required on my desktop, but not on this new machine. I'm looking for clues that might throw some light on the situation. Michael