Docker container with internet connection but no working DNS server

I’ve met a network setup where common DNS servers like 8.8.8.8 were not working and domain names could not be resolved inside Docker containers.

Find out the DNS servers on your system (I was using Ubuntu 16.04):

# Get the name of the interface you're using to connect to your network
ifconfig

# Then get DNS servers associated to it (I've used the first one in this list)
nmcli device show <interfacename> | grep IP4.DNS | awk '{print $2}'

Now you have two options (“x.x.x.x” will be the DNS you chose from above):

• You can run containers with the dns flag:

  docker run -tid --dns x.x.x.x ubuntu:16.04 bash

• Or, as I did, you can configure the DNS to be used automatically by all future containers:
  • open /etc/network/interfaces
  • add “dns-nameservers x.x.x.x” after “iface lo inet loopback”
  • restart interfaces: sudo ifdown -a && sudo ifup -a

    sudo sed -i '/iface lo inet loopback/a dns-nameservers x.x.x.x' /etc/network/interfaces
    sudo ifdown -a && sudo ifup -a