+=head2 Implementation/Debugging
+
+Implementation of delayed power off is a bit tricky because it uses
+C<sudo> in combination with several systemd services and timers. Here
+is a summary of the call chains in various situations. This might be
+useful for debugging.
+
+Powering on (via I<on> or I<console> subcommands):
+
+ novaboot-shell -c on
+ systemctl --user start novaboot-delayed-power-off.service
+ sudo novaboot-power on
+ systemctl stop "novaboot-power-off@${SUDO_USER}.timer"
+ systemctl start "novaboot-power@${SUDO_USER}.service"
+ novaboot-shell -c on (with $PPID = 1)
+ eval "$on_cmd"
+
+Powering off via explicit I<off> subcommand:
+
+ novaboot-shell -c off
+ sudo novaboot-power off
+ systemctl stop "novaboot-power@${SUDO_USER}.service"
+ novaboot-shell -c off (with $PPID = 1)
+ eval $off_cmd
+
+Delayed off (executed automatically as a stop job of
+novaboot-delayed-power-off.service at session end):
+
+ sudo novaboot-power delayed-off
+ systemctl start "novaboot-power-off@${SUDO_USER}.timer"
+ ...
+ novaboot-power-off@${SUDO_USER}.service conflicts novaboot-power@${SUDO_USER}.service
+ novaboot-shell -c off (with $PPID = 1)
+ eval $off_cmd
+