Error Code:
# chmod 644 resolv.conf
chmod: changing permissions of 'resolv.conf': Operation not permitted
Analysis:
This file is locked by chattr command
Solution:
Step One: Cancel the lock
# chattr -i /etc/resolv.conf
Step Two: Change the file’s privilege
# chmod 644 resolv.conf
Step Three: Relock this file
# chattr +i /etc/resolv.conf