Network calls fail during image build on corporate network

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I was able to figure out the issue. On Ubuntu, Docker sets the DNS servers for container to Google’s servers at 8.8.8.x. As I understand it, this is a workaround on Ubuntu due to the fact that Ubuntu sets /etc/resolv.conf to be 127.0.0.1.

Those Google servers weren’t accessible from behind our firewall, which is why we couldn’t resolve any URLs.

The fix is to tell Docker which DNS servers to use. This fix depends on how you installed Docker:

Ubuntu Package

If you have the Ubuntu package installed, edit /etc/default/docker and add the following line:

DOCKER_OPTS="--dns <your_dns_server_1> --dns <your_dns_server_2>"

You can add as many DNS servers as you want to this config. Once you’ve edited this file you’ll want to restart your Docker service:

sudo service docker restart

Binaries

If you’ve installed Docker via the binaries method (i.e. no package), then you set the DNS servers when you start the Docker daemon:

sudo docker -d -D --dns <your_dns_server_1> --dns <your_dns_server_2> &

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