GRUB_DEFAULT
Sets the default menu entry that will be booted next time the computer is rebooted.
It can be a numeric value, a complete menu entry quotation, or “saved”. A few
examples follow:
GRUB_DEFAULT=2 boots the third (counted from zero) boot menu entry.
GRUB_DEFAULT=2>0 boots the rst entry from the third submenu.
GRUB_DEFAULT="Example boot menu entry" boots the menu entry
whose title matches the quotation.
GRUB_DEFAULT=saved boots the entry specied by the grub2-reboot or
grub2-set-default commands. While grub2-reboot sets the default
boot entry for the next reboot only, grub2-set-default sets the default boot
entry until changed.
GRUB_SAVEDEFAULT
If set to true, it will automatically choose the last selected OS from the boot menu
as the default boot entry on the next boot. For this to work, you also need to specify
GRUB_DEFAULT=saved.
GRUB_HIDDEN_TIMEOUT
Waits the specied number of seconds for the user to press a key. During the period
no menu is shown unless the user presses a key. If no key is pressed during the
time specied, the control is passed to GRUB_TIMEOUT.
GRUB_HIDDEN_TIMEOUT=0 rst checks whether Shift is pressed and shows the
boot menu if yes, otherwise immediately boots the default menu entry. This is the
default when only one bootable OS is identied by GRUB2.
GRUB_HIDDEN_TIMEOUT_QUIET
If false is specied, a countdown timer is displayed on a blank screen when the
GRUB_HIDDEN_TIMEOUT feature is active.
GRUB_TIMEOUT
Time period in seconds the boot menu is displayed before automatically booting
the default boot entry. If you press a key, the timeout is cancelled and GRUB2
waits for you to make the selection manually. GRUB_TIMEOUT=-1 will cause
the menu to be displayed until you select the boot entry manually.
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