skúšal som to, mne tu funguje takto:
do sudoers som pridal NOPASSWD: /sbin/halt, takže teraz mi vyzerá takto
# /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
# Host alias specification
# User alias specification
# Cmnd alias specification
# Defaults
Defaults !lecture,tty_tickets,!fqdn
# User privilege specification
root ALL=(ALL) ALL
# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL, NOPASSWD: /usr/sbin/hibernate, /sbin/halt
s tým, že som členom členom skupiny admin a na ploche vytvoril späšťač s príkazom "sudo /sbin/halt"