+ <para>The boot menu is shown when a non-zero menu timeout has been configured. If the menu timeout has
+ been set to zero, it is sufficient to press any key — before the boot loader initializes — to bring up
+ the boot menu, except for the keys listed immediately above as they directly boot into the selected boot
+ menu item. Note that depending on the firmware implementation the time window where key presses are
+ accepted before the boot loader initializes might be short. If the window is missed, reboot and try
+ again, possibly pressing a suitable key (e.g. the space bar) continuously; on most systems it should be
+ possible to hit the time window after a few attempts. To avoid this problem, consider setting a non-zero
+ timeout, thus showing the boot menu unconditionally. Some desktop environments might offer an option to
+ directly boot into the boot menu, to avoid the problem altogether. Alternatively, use the command line
+ <command>systemctl reboot --boot-loader-menu=0</command> from the shell.</para>
+