Docker build “Could not resolve 'archive.ubuntu.com'” apt-get fails to install anything

Question

I\'ve been trying to run Docker build on various files which previously worked before, which are now no longer working.

As soon as the Docker file included any line

Answer 1

Uncommenting DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4" in /etc/default/docker as Matt Carrier suggested did NOT work for me. Nor did putting my corporation's DNS servers in that file. But, there's another way (read on).

First, let's verify the problem:

$ docker run --rm busybox nslookup google.com   # takes a long time
nslookup: can't resolve 'google.com'   # <--- appears after a long time
Server:    8.8.8.8
Address 1: 8.8.8.8

If the command appears to hang, but eventually spits out the error "can't resolve 'google.com'", then you have the same problem as me.

The nslookup command queries the DNS server 8.8.8.8 in order to turn the text address of 'google.com' into an IP address. Ironically, 8.8.8.8 is Google's public DNS server. If nslookup fails, public DNS servers like 8.8.8.8 might be blocked by your company (which I assume is for security reasons).

You'd think that adding your company's DNS servers to DOCKER_OPTS in /etc/default/docker should do the trick, but for whatever reason, it didn't work for me. I describe what worked for me below.

SOLUTION:

On the host (I'm using Ubuntu 16.04), find out the primary and secondary DNS server addresses:

$ nmcli dev show | grep 'IP4.DNS'
IP4.DNS[1]:              10.0.0.2
IP4.DNS[2]:              10.0.0.3

Using these addresses, create a file /etc/docker/daemon.json:

$ sudo su root
# cd /etc/docker
# touch daemon.json

Put this in /etc/docker/daemon.json:

{                                                                          
    "dns": ["10.0.0.2", "10.0.0.3"]                                                                           
}     

Exit from root:

# exit

Now restart docker:

$ sudo service docker restart

VERIFICATION:

Now check that adding the /etc/docker/daemon.json file allows you to resolve 'google.com' into an IP address:

$ docker run --rm busybox nslookup google.com
Server:    10.0.0.2
Address 1: 10.0.0.2
Name:      google.com
Address 1: 2a00:1450:4009:811::200e lhr26s02-in-x200e.1e100.net
Address 2: 216.58.198.174 lhr25s10-in-f14.1e100.net

REFERENCES:

I based my solution on an article by Robin Winslow, who deserves all of the credit for the solution. Thanks, Robin!

"Fix Docker's networking DNS config." Robin Winslow. Retrieved 2016-11-09. https://robinwinslow.uk/2016/06/23/fix-docker-networking-dns/