In Linux /etc/resolv.conf get often overwritten when we setup the DNS, because of the multitude of programs managing the DNS servers, making a proper setup complicated sometimes.
DNS Config Under Linux
DNS usage on linux is done over a set of routines in the C library that provide access to the Internet Domain Name System (DNS). The resolver configuration file (resolv.conf) contains information that is read by the resolver routines the first time they are invoked by a process. In short each process requesting DNS will read /etc/resolv.conf over library. The NSS is layered on top of this, and is configured by /etc/nsswitch.conf.
On a Linux system using EXT3, EXT4, BTRFS or else there are multiple tools to recover deleted or lost files, the BTRFS file system makes the recovery process more easy and with a higher success rate compared to EXT3/EXT4 where file recovery can be sometimes impossible.