I’ve already written about creating a partition size larger than 2TB under Linux using GNU parted command with GPT. In this tutorial, I will provide instructions for booting to a flat 2TB or larger RAID array under Linux using the GRUB boot loader.
Describes how to boot dual boot FreeBSD and Linux operating system using GNU boot loader called Grub (GRand Unified Bootloader)
You can set a password for the GRUB bootloader. This prevents users from entering single user mode or changing settings at boot time.
When your system is rebooted, grub presents the boot option menu. From this menu one can easily login into a single user mode without the password which might result into compromise system security.
For example, anyone can access the data or change the settings. However you can setup a password for grub with password option. This option forces grub to ask for a password before making any changes or entering into single user mode. You need to type p followed by password.