Systemd comes with its own implementation: systemd-resolved. Ubuntu included systemd-resolved in version 16.10 and it’s now present in latest 18.04. These cause resolv.conf use 127.0.0.53 and in many case make system cannot resolve name.
I found some tricks to slove this issue.
/etc/systemd/resolved.confreplace DNS_IPx with your DNS’s IP
[Resolve] DNS=DNS_IP1 DNS_IP2 DNS_IP3 #FallbackDNS= #Domains= #LLMNR=no #MulticastDNS=no #DNSSEC=no #Cache=yes #DNSStubListener=yes
- Make link resolv.conf
ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf
- Restart systemd-resolved
systemctl restart systemd-resolved