title: Docker run - apk update - could not connect to server
body: <p>I'm trying to run a simple alpine docker image on rhel 7, but i'm stuck in this error when i run apk update: </p>
  
  <pre><code>fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
  ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.10/main: could not connect to server (check repositories file)
  WARNING: Ignoring APKINDEX.00740ba1.tar.gz: No such file or directory
  fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
  ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.10/community: could not connect to server (check repositories file)
  WARNING: Ignoring APKINDEX.d8b2a6f4.tar.gz: No such file or directory
  2 errors; 14 distinct packages available
  </code></pre>
  
  <p>I run these commands:</p>
  
  <pre><code>docker run -it --rm --env="http_proxy=http://127.0.0.1:3128" alpine /bin/sh
  apk update
  </code></pre>
  
  <p>I'm behind a ssh tunnel proxy in the virtual machine.
  I've set /etc/docker/daemon_config.json, /etc/systemd/system/docker.service.d/http.proxy.d, enviroment variables and dns.</p>
  
  <p>What can i do?</p>