The GRUB password only is useful at the bootloader, before any operating
system is booted. If you have access to the bootloader interface, then you
have a physical access to the computer and there basically is no security
(you can boot a live system and do whatever you want). In other words, the
GRUB password is useless. I would even say it is an annoyance when a broken
system is to be recovered. That is why, on my systems, I commented all lines
in /etc/grub.d/01_PASSWORD. Notice that the developers of GNU GRUB do not say
otherwise ( https://www.gnu.org/software/grub/manual/grub.html#Security ):
By default, the boot loader interface is accessible to anyone with physical
access to the console: anyone can select and edit any menu entry, and anyone
can get direct access to a GRUB shell prompt. For most systems, this is
reasonable since anyone with direct physical access has a variety of other
ways to gain full access, and requiring authentication at the boot loader
level would only serve to make it difficult to recover broken systems.
If you want potential robbers of your physical disk to not be able to read
your data, then encrypt the /home partition (and the swap partition if you
have one). Again: the GRUB password is no security.
Once the operating system is booted, the GRUB password is totally useless. As
other users explained you, Trisquel does not have a root user by default. You
just precede commands with 'sudo' when a user with administrative privileges
has to perform some administrative tasks. His/her password is then asked (it
must be a good password:
http://www.baekdal.com/insights/password-security-usability) and
administrative tasks can only be performed during a short period of time
(five minutes is the default I believe) without reentering the password. It
is therefore more secure than a root terminal.
Anyway you can get a root terminal if you wish:
$ sudo -i
You can even get a root user if you really want to. Just give that user a
password:
$ passwd root
