Пробовал уже практически все - ничего не помогает. Пукты «выключить» и «перезагрузить» недоступны. Приходится логиниться в рута и выключать через него.
/etc/sudoers:
#
# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults env_reset
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:$
Defaults env_keep += "HOME"
##
## X11 resource path settings
Defaults env_keep += "XAPPLRESDIR XFILESEARCHPATH XUSERFILESEARCHPATH"
##
## Desktop path settings
Defaults env_keep += "QTDIR KDEDIR"
##
## Allow sudo-run commands to inherit the callers' ConsoleKit session
Defaults env_keep += "XDG_SESSION_COOKIE"
##
## Uncomment to enable special input methods. Care should be taken as
## this may allow users to subvert the command being run via sudo.
Defaults env_keep += "XMODIFIERS GTK_IM_MODULE QT_IM_MODULE QT_IM_SWITCHER"
# Host alias specification
# User alias specification
# Cmnd alias specification
# User privilege specification
root ALL=(ALL:ALL) ALL
alex ALL=(ALL:ALL) ALL
# Allow members of group sudo to execute any command
%sudo ALL=(ALL:ALL) ALL
# See sudoers(5) for more information on "#include" directives:
alex AC-XFCE-LAPTOP = NOPASSWD: /usr/lib/xfce4/session/xfsm-shutdown-helper
#includedir /etc/sudoers.d
