ReaR バックアップがエラー "ERROR: No nameserver or only loopback addresses in /root/rear.xxx/rootfs/etc/resolv.conf" で失敗する理由

Issue

• Rear バックアップの作成が、以下のエラーで失敗します。

ERROR: No nameserver or only loopback addresses in /root/rear.xxx/rootfs/etc/resolv.conf, specify a real nameserver via USE_RESOLV_CONF
Some latest log messages since the last called script 630_verify_resolv_conf_file.sh:
  2023-06-09 18:18:25.606255145 Including build/GNU/Linux/630_verify_resolv_conf_file.sh
Aborting due to an error, check /var/log/rear/rear-xxx.log for details
Exiting rear mkbackup (PID xxx) and its descendant processes ...
Running exit tasks
Terminated