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Seatd is a minimal seat management daemon, and a universal seat management library. Seat management takes care of mediating access to shared devices (graphics, input), without requiring applications like Wayland compositors being granted root privileges.
USE flags for sys-auth/seatd Minimal seat management daemon and universal library
emerge --ask sys-auth/seatd
To use seatd service, builtin and server USE flags are required. In addition, to have access to seatd, it is required to be part of the video and seat groups:
gpasswd -a larry video
gpasswd -a larry seat
Add the seatd daemon to the default runlevel so that seat management is provided on system startup:
rc-update add seatd default
Start the seatd daemon now:
rc-service seatd start