Prevent files from being changed (chattr)

Note: Please only do this if you know what you are doing. Using this method on the wrong files could result in unexpected behavior of your system, make sure you understand what you are doing before you continue.

In this example we will use the "/etc/resolv.conf" file.

# To "lock" a file:
$ sudo chattr +i /etc/resolv.conf

# To "unlock" a file:
$ sudo chattr -i /etc/resolv.conf