Temporary failure resolving 'deb.debian.org'

i am using debian 9 on bbb over NFS using ethernet cable and not able to access internet, screenshot attached below please help

Screenshot from 2020-10-16 11:44:35.png

WHY a screen grab image? That's a text console, just select the text,
copy, and paste into a message.

  NFS is just a network shared file system.

  apt update/upgrade requires an internet connection -- if you don't have
a viable internet connection there is nothing to be done. If, OTOH, you do
have an internet connection -- you may just have to wait a day and retry,
as something may be down between you and the repository machine.

can you ping
if not, then does /etc/resolv.conf have “nameserver” or “nameserver”?
if nameserver is not in resolv.conf, you need to add one there.
If you have the above, then there is some other issue. need more info
like does your board have an ip.