No network request working from a docker when building docker image

Question

I'm trying to build docker image with Dockerfile. For the experiment, I added to this file such lines:

RUN ping google.com
RUN ping 8.8.8.8

Then I'm trying to build this image:

docker build -t my-custom-python:latest -f ./Dockerfile

And this code not working properly. For ping commands it says:

ping: bad address 'google.com'

If I remove this lines, then it executes command:

RUN pip wheel --wheel-dir=/wheels -r /requirements/dev.txt

it reads my requiremets/dev.txt file, sees such line:

git+git://github.com/bpython/bpython.git

And after this it says:

Running command git clone -q git://github.com/bpython/bpython.git /tmp/pip-req-build-o8c7n380 fatal: unable to look up github.com (port 9418) (Try again) ERROR: Command errored out with exit status 128: git clone -q git://github.com/bpython/bpython.git /tmp/pip-req-build-o8c7n380 Check the logs for full command output.

It seems there is a problem with DNS, and (as I noticed) it started when I install ExpressVPN. But in my host machine ping and git clone works.

I also tried to disable VPN - nothing changes. I don't know how to ckeck if DNS works insight Docker or how to fix it.

Please, need your help!

Answer 1

This post was very helpfull for me: My docker container has no internet

I changed resolv.conf on my host machine (Ubuntu 18.04):

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

And after this, I recreated Docker configs:

pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
docker -d

Now, everything works fine.