How to disable systemd-resolved in Ubuntu?

This method works on the Ubuntu releases 17.04 (Zesty), 17.10 (Artful), 18.04 (Bionic), 18.10 (Cosmic), 19.04 (Disco) and 20.04 (Focal):

Disable and stop the systemd-resolved service:

sudo systemctl disable systemd-resolved
sudo systemctl stop systemd-resolved

Then put the following line in the [main] section of your /etc/NetworkManager/NetworkManager.conf:

dns=default

Delete the symlink /etc/resolv.conf

rm /etc/resolv.conf

Restart NetworkManager

sudo systemctl restart NetworkManager

Also be aware that disabling systemd-resolvd might break name resolution in VPN for some users. See this bug on launchpad (Thanks, Vincent).

I've recently upgraded to (k)Ubuntu 17.04 and I also stumbled upon the change to systemd.

My setup is fairly typical I think, in that I have a DNS provider in my broadband HUB and this is my primary source of information for all the devices on my network (of which I have a few).

There is some beauty in systemd, it's not all bad but what is really bad is the documentation, the lack of communication from the Ubuntu team and the gung-ho "let's just change it despite it breaks for everyone" mentality.

The solution for me after tearing some hair out was to edit /etc/systemd/resolved.conf:

[Resolve]
DNS=192.168.1.254   # <-- change to your router address
#FallbackDNS=8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844
Domains=lan         # <-- change to your localdomain name (maybe .local)
#LLMNR=yes  <-- I dabbled with this for a while but it doesn't matter
#DNSSEC=no
#Cache=yes
#DNSStubListener=udp

After not understanding why this wouldn't work I figured out that what was also needed was to switch /etc/resolv.conf to the one provided by systemd. This isn't the case in an out-of-a-box install (for reasons unknown to me).

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

The local DNS server is then not used and all DNS requests are sent to my HUB.

I think this is a much better solution than cutting out and putting in some other solution since systemd-resolv is now the default onwards.

A related problem btw is that the /etc/nsswitch.conf is neutered.

It should read:

hosts: files mdns4_minimal dns [NOTFOUND=return] resolve [!UNAVAIL=return] dns

This is a confusing configuration since [NOTFOUND=return] means processing ends there. The entries after it will never be used.

If you are using Ubuntu 18.04 Server, none of these answers apply. The one by user2427436 comes closest.

The issue is that systemd-resolved is/runs a stub resolver, and I just need to completely disable that (per the question). I need to do this because Zimbra 8.8.15 (FOSS) comes with its own integrated resolver (unbound).

In my situation I am starting from a stock (naive) install of server 18.04, with minimal options on bare metal (well, actually a VM).

so here's the recipe:

   vi /etc/systemd/resolved.conf
     edit line #DNSStubListener=yes
         to be DNSStubListener=no
   systemctl stop systemd-resolved
   systemctl status systemd-resolved
   rm /etc/resolv.conf
   reboot to test...

This is what /etc/systemd/resolved.conf looks like now:

# See resolved.conf(5) for details
[Resolve]
#DNS=
#FallbackDNS=
#Domains=
#LLMNR=no
#MulticastDNS=no
#DNSSEC=no
#Cache=yes
#DNSStubListener=yes
DNSStubListener=no

that's all it took.

Feel free to install any other resolver you want after this.