Every time that I start my computer, my DNS does not work. In /etc/resolv.conf I see:
# Generated by Connection Manager
nameserver ::1
nameserver 127.0.0.1
I see that /etc/resolv.conf is a soft link to /run/connman/resolv.conf
With this configuration, my DNS does not work (example: cannot surf the web with Chrome/Firefox, dig google.com gives me no IP, and ping gives me "Name or service not known").
So, I manually change the nameserver ::1 with some valid IP (like 1.1.1.1 or 8.8.8.8). I need to do this every time that I turn on my computer.
I don't know if connman (Intel Connection Manager daemon) comes preinstalled in Ubuntu 17.10, or I have installed it when trying to install a VPN client. Searching on the web, it seems that I don't have a standard configuration. So, I tried stopping the service, but then I lose my connections and don't see the available networks in the (NetworkManager?) Applet.
I can see that connmand is listening on port 53 (but does not resolve well), and systemd-resolve is also listening on port 53 (but attached to 127.0.0.53):
sudo netstat -tulpn | grep ":53 "
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 21159/connmand
tcp6 0 0 ::1:53 :::* LISTEN 21159/connmand
udp 0 0 127.0.0.1:53 0.0.0.0:* 21159/connmand
udp 0 0 127.0.0.53:53 0.0.0.0:* 1451/systemd-resolv
udp6 0 0 ::1:53 :::* 21159/connmand
If I execute systemd-resolve --status, it gives me the correct DNS.
Relinking /etc/resolv.conf to /run/systemd/resolve/resolv.conf also solves my problem.
So, how can I disable connman (at least as the DNS proxy) and reenable systemd-resolve? Is connman installed by default on Ubuntu 17.10?