I've recently upgraded to 17.10. When I try to browse to a website, or ping a domain it fails saying the site cannot be resolved.

network-admin shows the contents of /etc/resolv.conf to be nameserver: 127.0.0.53

If I change that to 8.8.8.8 or 208.67.222.222 then everything works. Until I reboot.

Upon reboot or resume, the nameserver is reset to 127.0.0.53.

How do I permanently set the nameserver to something that works?

For systemd fans, if I run systemd-resolve --status I get

Link 3 (wlo1)

      Current Scopes: LLMNR/IPv4 LLMNR/IPv6

       LLMNR setting: yes

MulticastDNS setting: no

      DNSSEC setting: no

    DNSSEC supported: no

If I follow the advice at this question - DNS keeps resetting after reboot. Ubuntu 17.10 - DNS still fails to resolve.

You can install a package resolvconf, which will modify the way /etc/resolv.conf is built up at system boot.

sudo apt install resolvconf

You can then create or modify a file /etc/resolvconf/resolv.conf.d/tail. If you put in this file a line nameserver 8.8.8.8, this line will be added at the end of /run/resolvconf/resolv.conf at boot. /etc/resolv.conf will now be a symbolic link to this file.

I use Lubuntu & Kubuntu 18.04. I was able to overcome the DNS problem in 2 steps:

First step: Install unbound and set it to replace systemd-resolved as Grégoire C shows here.

sudo systemctl disable systemd-resolved

sudo systemctl stop systemd-resolved

sudo systemctl enable unbound-resolvconf

sudo systemctl enable unbound

reboot

Open as root the file /etc/NetworkManager/NetworkManager.conf

(sudo leafpad /etc/NetworkManager/NetworkManager.conf in Lubuntu 18.04 or in Kubuntu 18.04 SUDO_EDITOR=kate sudoedit /etc/NetworkManager/NetworkManager.conf)

and below [main] put this line:

dns=unbound

reboot again

Second step: If after the reboot the problem is still not solved, as it was in my case, start the file manager as root, go to /etc, delete resolv.conf and create a new resolv.conf. Leave it empty and reboot the OS. In my case after this reboot the problem disappeared.

In Kubuntu 18.04 you can't start Dolphin as root, so you can first go to /etc and open the terminal from there, then type sudo su and press Enter to use it as root and then delete resolv.conf with the command rm resolv.conf. Then you can create a new empty file on your desktop, name it resolv.conf and open a terminal from there. Use the sudo su command to enter the root mode for the terminal and then copy the new resolv.conf from your desktop to /etc with the command cp resolv.conf /etc.

I have to add that I did not try to do the second step before installing unbound, so the next time I will do so, just to see if it will be enough or not.

working within the systemd paradigm add a DNS to a link / device

• systemd.network manual page

using ubuntu 17.10+ add a *.network file:

sudo nano /lib/systemd/network/100-somecustom.network:

100-somecustom.network ( 100 can be any number for priority, and it requires the .network file extension ):

[Match]

Name=wlo1 # the device name here



[Network] # add multiple DNS 

DNS=8.8.8.8

DNS=208.67.222.222

Then restart:

sudo service systemd-networkd restart

Also look into:

netplan apply

Then check:

systemd-resolve --status wlo1

From info page info systemd.network :

In addition to /etc/systemd/network, drop-in ".d" directories can be
placed in /lib/systemd/network or /run/systemd/network directories.
Drop-in files in /etc take precedence over those in
/run which in turn take precedence over those in /lib. Drop-in files under any of these directories take precedence over the main
netdev file wherever located. (Of course, since /run is
temporary and /usr/lib is for vendors, it is unlikely drop-ins should be used in either of those places.)

Another approach disable the DNSStubListener for usage with dnsmasq:

sudo nano /etc/systemd/resolved.conf:

#

DNSStubListener=false

related:

• https://superuser.com/questions/1153203/ubuntu-17-04-systemd-resolved-dns-lookups-randomly-fail


• DNS at systemd's 127.0.0.53 is ignoring some lookups


• https://unix.stackexchange.com/questions/304050/how-to-avoid-conflicts-between-dnsmasq-and-systemd-resolved

Why won't you just fix resolved and avoid trying to cure migraine with a guillotine?

Just put 8.8.8.8 or whatever you need in DNS= configuration of /etc/systemd/resolved.conf, then restart systemd-resolved.service.