if you want a file not to be modified by anyone even the root user

Suppose you have a file which you never want any one to delete, modify, move here is the option you have......

This is called an immutable file which is supported in linux ext2/ext3

which you can do as follow:

suppose you want to create a file called configuration which you never wanted to be modified move or removed the what you can do is follows:

chattr +i configuration

after doing that this file configuration cant be deleted,moved or changed

if you want it to simple file again you  can do

chattr -i configuration