Name resolution issues inside a Dockerfile

Issue: When building a docker container from a Dockerfile, commands like RUN apt update and RUN git clone <repository> fail with name resolution errors. At the same time, these commands work inside a running container. This is particularly likely for VMs and bare-metal instances with only IPv6 address and no IPv4 address.

Workaround:

• Check your docker configuration, by default at /etc/docker/daemon.json and make sure IPv6 support is enabled. The relevant part of configuration should look like

  BASH

  {
    ...
    "ipv6": true,
    "fixed-cidr-v6": "fd80:0000:0000:0000:1000::/68",
    "experimental": true,
    "ip6tables": true,
    "default-address-pools":[
      {"base": "172.31.0.0/16", "size": 24},
      {"base": "fd80:0000:0000:0000:2000::/68", "size": 80}
    ],
    ...
  }

• Taiga cloud images with pre-installed docker have this configuration out-of-the-box