Q. I’m getting following error on my Debian Linux system:

mv cannot move /etc/resolv.conf.dhclient-new to /etc/resolv.conf: Operation not permitted

How do I fix this problem?

A. This error indicate that dhclient (Dynamic Host Configuration Protocol Client) is not able to update your name resolution configuration file /etc/resolv.conf. To fix this error

Run dhclient as root user

Use sudo command to run dhclient, enter:
$ sudo dhclient eth0

Make sure /etc/resolv.conf is not write protected

Use lsattr, command to view file attributes:
$ lsattr /etc/resolv.conf
Output:

----i------------- /etc/resolv.conf

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 for any user including root user. Clear i attribute, enter:
$ sudo chattr -i /etc/resolv.conf
Now run dhclient again to update file and to obtained new IP address.