Tricks to avoid DHCP client to override /etc/resolv.conf

I have a laptop installed with Ubuntu and is using DHCP client to connect to the Internet in couples of locations. Most of the DHCP server love to offer DHCP IP bundled with DNS addresses which is kind of convenience if one dont have their own DNS. For some reason, I have to use my own DNS server to perform DNS lookup and this DHCP kindness is getting annoying as I have to update the resolv.conf everytime I got the DHCP IP.

Just think of a trick to lock the /etc/resolv.conf from overwriting by doing chattr +i, i.e.

[root@ ~]# lsattr /etc/resolv.conf
------------- /etc/resolv.conf
[root@ ~]# chattr +i /etc/resolv.conf
[root@ ~]# lsattr /etc/resolv.conf
----i-------- /etc/resolv.conf

After that the file /etc/resolv.conf would be locked from writing until removal of this tag. I tested it by appending some crap to the /etc/resolv.conf but it doesnt allow me to write over.

[root@ ~]# echo some-crap >> /etc/resolv.conf
-bash: /etc/resolv.conf: Permission denied

Now I could keep using my own DNS and no need to update the file all the time.

Falling back is easy.

[root@ ~]# chattr -i /etc/resolv.conf
[root@ ~]# lsattr /etc/resolv.conf
------------- /etc/resolv.conf