NetworkManager writing to resolv.conf every reboot, breaking dnsmasq?

Question

I am on Ubuntu 18.04 using the netplan configuration which renders using NetworkManager:

# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

Every time I restart, the following output is automatically generated and written to /etc/resolv.conf, breaking my dnsmasq configuration in that I can no longer resolve domains on the internet:

# Generated by NetworkManager
nameserver 127.0.0.53

I can fix this manually by simply commenting out the nameserver line in /etc/resolv.conf. Before I write a script to perform this commenting out every reboot, I should understand what's going on.

This is my simple /etc/dnsmasq.conf:

port=53
domain-needed
bogus-priv
strict-order

server=/mydomain.net/10.0.0.2
server=/#/8.8.8.8

listen-address=127.0.0.1

bind-interfaces 

1) Why is this being written by NetworkManager every reboot?

2) Why is it breaking dnsmasq anyway because the strict-order server settings should forward all other requests to google's DNS server? When dnsmasq is running, does the system look in resolv.conf first or after dnsmasq.conf?

Solution

Same problem with dnsmasq:

1. Edit /etc/NetworkManager/NetworkManager.confand after [Main] add or change to dns=none. Save the file.
2. Execute systemctl restart NetworkManager.service (please note uppercase and lowercase).
3. Edit /etc/resolv.conf with your values. Save the file.

Optional testing: reboot and confirm.

Hope be useful, thanks for your attention.

Comments

[Boris Hamanov]

The problem is due to a couple of problems. Understand that DNS in 18.xx is kinda screwball. Edit your question with the output from ls -al /etc/resolv.conf and ps auxc | grep dns and ps auxc | grep resolv and cat /run/resolvconf/resolv.conf and cat /run/systemd/resolve/resolv.conf. Are you using dnsmasq for DNS, or DHCP? Did you install it, or did it come over from an upgrade?

[sphere]

I totally don't understand what's going on - why does dnsmasq only work when the contents of /etc/resolv.conf are empty if systemd-resolvd is disabled?

[Boris Hamanov]

If you respond to my earlier comment, I'll have some info to go on. Also show me cat /etc/NetworkManager/NetworkManager.conf.

[MBulava]

OMG thatnks a ton! NetworkManager and dnsmasq have been a thorn in my side for the last week