Cfrgtkky

During Ubuntu Server 18.04 installation, I provided the wrong DNS server, say 192.168.0.1. I now want to change it to a different server, say 8.8.8.8, but cannot find the correct spot to do this.

I know that I can configure the global DNS settings in /etc/systemd/resolved.conf. Although this fixes the problem, I am still seeing the original wrong server entry in systemd-resolve --status:

Global

     DNS Servers: 8.8.8.8

      DNSSEC NTA: 10.in-addr.arpa

                  16.172.in-addr.arpa

                  168.192.in-addr.arpa

                  17.172.in-addr.arpa

                  18.172.in-addr.arpa

                  19.172.in-addr.arpa

                  20.172.in-addr.arpa

                  21.172.in-addr.arpa

                  22.172.in-addr.arpa

                  23.172.in-addr.arpa

                  24.172.in-addr.arpa

                  25.172.in-addr.arpa

                  26.172.in-addr.arpa

                  27.172.in-addr.arpa

                  28.172.in-addr.arpa

                  29.172.in-addr.arpa

                  30.172.in-addr.arpa

                  31.172.in-addr.arpa

                  corp

                  d.f.ip6.arpa

                  home

                  internal

                  intranet

                  lan

                  local

                  private

                  test



Link 2 (ens3)

   Current Scopes: DNS

   LLMNR setting: yes

   MulticastDNS setting: no

   DNSSEC setting: no

   DNSSEC supported: no

   DNS Servers: 192.168.0.1

   DNS Domain: xyz.com

If I try to use sudo systemd-resolve --interface ens3 --set-dns 8.8.8.8 to change it, I get an error message:

The specified interface ens3 is managed by systemd-networkd. Operation refused.

Please configure DNS settings for systemd-networkd managed interfaces directly in their .network files.

Unfortunately, the /etc/systemd/network/ directory is empty. There are no *.network files there.

However, I found a config file in /run/systemd/network/10-netplan-ens3.network where I can change the entry, but it gets reset to the wrong value after I do

sudo systemctl daemon-reload

sudo systemctl restart systemd-networkd

sudo systemctl restart systemd-resolved

Now, how do I change the link specific setting permanently?

Edit: Thanks for the input!

I changed the DNS server in /etc/netplan/01-netcfg.yaml

Output cat /etc/netplan/01-netcfg.yaml:

# This file describes the network interfaces available on your system

# For more information, see netplan(5).

network:

  version: 2

  renderer: networkd

  ethernets:

    ens3:

      addresses: [ 192.168.0.2/24 ]

      gateway4: 192.168.0.1

      nameservers:

        search: [ xyz.com ]

        addresses:

            - "8.8.8.8"

(Maybe the spaces are not entirely correct because of pasting...)

Edit 2: I double checked the spaces

Edit 3: The answer of @George Udosen fixed the problem, thank you very much.

Output of sudo netplan --debug apply:

** (generate:10422): DEBUG: 00:54:03.168: Processing input file //etc/netplan/01-netcfg.yaml..

** (generate:10422): DEBUG: 00:54:03.168: starting new processing pass

** (generate:10422): DEBUG: 00:54:03.169: ens3: setting default backend to 1

** (generate:10422): DEBUG: 00:54:03.169: Generating output files..

** (generate:10422): DEBUG: 00:54:03.169: NetworkManager: definition ens3 is not for us (backend 1)

DEBUG:netplan generated networkd configuration exists, restarting networkd

DEBUG:no netplan generated NM configuration exists

DEBUG:device lo operstate is unknown, not replugging

DEBUG:netplan triggering .link rules for lo

DEBUG:device ens3 operstate is up, not replugging

DEBUG:netplan triggering .link rules for ens3

systemd-resolve --status now lists the correct DNS server:

...

Link 2 (ens3)

  Current Scopes: DNS

   LLMNR setting: yes

   MulticastDNS setting: no

   DNSSEC setting: no

   DNSSEC supported: no

   DNS Servers: 8.8.8.8

   DNS Domain: xyz.com

Edit your netplan configuration file and remove the old dns server names and add new ones. Edit the file with sudo nano /etc/netplan/01-netcfg.yaml and yours should be similar to the example below:

networks:

    version:2 

    renderer: networkd

    ethernets:

         enp0s3:

             dhcp4: true

             nameservers:

                  search: [mydomain, otherdomain]

                  addresses: [10.10.10.1, 1.1.1.1]

The line of interest is the one that says addresses under the settings nameserver. It might also be written like so:

nameservers:

     search: 

         - mydomain

         - otherdomain

     addresses:

         - "10.10.10.1"

         - "1.1.1.1"

Change the address there to the one you desire. Make sure to observe the indentations as ther are. Now after thatv save the file and aplly the changes:

sudo netplan --debug apply