#6 Docker container can reach DNS but not resolve Hosts

closed
Josep Maria Bernabe
None
Doubt
PaaS4SLA
2016-10-03
2016-09-30
David Aleixo
No

when running the following command, the Docker Container cannot compile returning the following output:

Cmd: docker run --rm -v $(pwd):/tmp/component c2netproject.eu/runtime/java/dev:1_0_0 -c 'cd /tmp/component && npm install’

Cmd output:Attached

1 Attachments
log compilation.log

Discussion

  • Josep Maria Bernabe
    Josep Maria Bernabe
    2016-10-03

    Just for the record, this doubt has been previously sent and resolved via email.

    In this case, the problem came from the name resolution server (DNS) configuration mixed with some sort of external DNS blocking performed by UNINOVA's internal network. The solution, found by David Aleixo, was to change that configuration to use the global DNS used by the internal network. The steps suggested by David Aleixo are the following:

    1. The docker host must have IP Forwarding enabled:
      $ net.ipv4.ip_forward = 1
    2. I have disabled the dnsmasq in order to use the global DNS
    3. In some cases, additional firewall config should be done in order to ensure that fw "forwards the traffic to the Docker's bridge network"
      DEFAULT_FORWARD_POLICY = ACCEPT (for ufw)
    4. You were right. I guess our internal network is somehow blocking external DNS, thus DOCKER_OPTS was updated to hit the "internal" DNS, or more easly, as you said just using "--dns" will do the job as well.
     
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  • Josep Maria Bernabe
    Josep Maria Bernabe
    2016-10-03

    • status: open --> closed
     
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