Proxy Settings for Docker Private Registry in VMs

Question

Hi folks and colleagues I'm running out of ideas.

My main problem is that my docker client VM can't connect to the private registry in another VM and throws the error:

user@ubuntu:~$ docker push 192.168.14.147:5000/hello-world The push refers to repository [192.168.14.147:5000/hello-world] Get https://192.168.14.147:5000/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

My current setup:

• One VM (Ubuntu 16.03) where I run my docker registry on port 5000 (VM-IP: 192.168.14.147)
• When I tried to push/pull on the registry VM with docker push 127.0.0.1:5000/hello-world it pushes and pulls the tagged image correct, so the registry is working
• One VM (Ubuntu 16.03) where I run my docker "client" and want to push/pull (VM-IP: 192.168.14.148)
• I can contact both VM successful via ping 192.168.14.147 (.148) in the terminal
• Both VMs have following (fully working) proxy settings provided via bash script:

echo "export http_proxy=http://10.8.31.1:8080
export https_proxy=http://10.8.31.1:8080" >> /etc/bash.bashrc
echo "export http_proxy=http://10.8.31.1:8080
export https_proxy=http://10.8.31.1:8080" >> /etc/environment
echo "Acquire::http::Proxy \"http://10.8.31.1:8080\";
Acquire::https::Proxy \"http://10.8.31.1:8080\";" >> /etc/apt/apt.conf

and the (working) Docker Environment is specified as

 echo "[Service]
 Environment=\"HTTP_PROXY=http://10.8.31.1:8080/\""  /etc/systemd/system/docker.service.d/http-proxy.conf
 touch /etc/systemd/system/docker.service.d/https-proxy.conf
 echo "[Service]
 Environment=\"HTTPS_PROXY=https://10.8.31.1:8080/\""  /etc/systemd/system/docker.service.d/https-proxy.conf

• Both VM are running on on the same host machine
• Self signed certificates are provided following this guide

At home I cloned this setup without the proxy and it works very well. so it seems to be a lack of knowledge regarding the network/proxy issue and not the certificates.

I tried this solution in the docker http(s)-proxy.conf

[Service] Environment="HTTP_PROXY=http://10.8.31.1:8080/" Environment="NO_PROXY=192.168.14.147"

because maybe it's forwarded to the proxy and can't find the registry IP there but that didn't work.

I invested a lot of effort in this topic and any help would be very appreciated.