chattr - change file attributes on a Linux file system

This command can be helpful, when set to use Public Google DNS on your computer.

If your ISP assigned you DNS, it will request every time your computer boots.

chattr - change file attributes on a Linux file system

The  operator `+' causes the selected attributes to be added to the existing attributes of the files; `-' causes them to be removed; and `=' causes them to be the only attributes that the files have.

immutable (i)

A file with the `i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can  be  written to the file.  Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

So you can block your /etc/resolv.conf file as root user.

chattr +i /etc/resolv.conf  


unlock

chattr -i /etc/resolv.conf

More information on chattr man page.