How to set grub menu password so that no one can change your password through recovery mode option in an ubuntu.it is very important for security reasons. i am going to show you how it can be done.The steps are given below to set grub menu password in an ubuntu.

1.first gain the root privilages by typing
$sudo su
you will be asked for password give it

2.By default root doesn't have a password ,so first set the root password by going to the termina
# passwd
you will be asked for a password two times
now you have set the root password.

3.go to the file called shadow by typing
~#cd /etc && nano shadow
4.copy the root password from there
the second field something like
root:$$45678888999$$$:kfjf

5.go to the menu.lst file by typing
~#cd /boot/grub/ && nano menu.lst

6.now find the line
##password --m5 passwd

uncomment that line and paste root password in the place of passwd
7.find the line #password topsecret
uncomment that also

8.now you are done next time when you go into the recovery mode you will be asked for password
9.now you have saved your computer of being getting hacked
10.ok thanks bye-bye

If someone has physical access, that won't be sufficient, they'll just use the install media in rescue mode.
To be more secure you need to disable the cd drive at least.
Maybe add a bios passwd. If they can take the disk out, you need encryption....

yes if someone has physical access to your pc,it'll easy to hack ur pc in rescue mode...

If you give someone physical access to your server/computer then you are just asking for trouble if you are trying to be security conscious and you don't trust the people around your computer. If you give me physical access to your computer, there is no type of software or encryption device that can keep me away from your data! Simple! If it can be made, it can be cracked! The first rule of computer security is common sense. If you cannot trust your environment, pick another environment! Good luck!