Executing script to affect non-root x session as root

X can have two ways of authorizing clients. One way is using cookies; then you have to set DISPLAY=:0 and XAUTHORITY=/home/yourusername/.Xauthority.

In your case I assume it is done with xhost, otherwise setting DISPLAY would not be enough. Type xhost to see who is authorized.

Maybe you have an ~/.Xauthority cookie along with xhost +SI:localuser:toothrot authorization.

You can allow root to access display :0 with DISPLAY=:0 xhost +SI:localuser:root, but you have to do it as normal user. Using the cookie is the better way:

DISPLAY=:0 XAUTHORITY=/home/toothrot/.Xauthority notify-send hullo 

To execute notify-send as user:

su toothrot -c 'DISPLAY=:0 XAUTHORITY=/home/toothrot/.Xauthority notify-send hullo' 

Presumably you solved your issue long ago, but for the sake of completion a general solution is (adapted from here):

$ my_user="toothrot" $ my_user_id=$(more /etc/passwd | awk -F: '/^'${my_user}':/ {print $3}') $ sudo -u $my_user DISPLAY=':0' DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/${my_user_id}/bus /usr/bin/notify-send "hullo" 

If you have several displays of screen sessions, your mileage may vary as far as DISPLAY=":0" is concerned in the above. That'd be for a different post though.

The above answers are kind of crufty, and don't work cleanly for multiple users or multiple displays. There could be a privilege escalation attack if a user symlinks ~/.Xauthority to a protected file. An alternative might be to forget udev entirely and instead use uudev, which runs as non-root in your own X session. You just set up a ~/.config/uudev.conf file that contains:

* ACTION="bind", DRIVER="whatever", ... notify-send hullo 

If you run systemctl --user restart uudev from within your ~/.xsession or ~/.xinitrc file, then notify-send will just get run with the appropriate DISPLAY and XAUTHORITY variables already set.