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/
newgrp docker
instead of doing a full log off then login after giving myselfsudo usermod -aG docker myuserid
... its an edge case for sure however it does happen – Outcrydocker compose build
fixed the problem. I don't know which requests should be allowed. – Wivern