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Merge pull request #4265 from unclejack/explain_networkmanager_and_dns_problems

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docs: explain DNS warnings & how to fix them
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Sven Dowideit 2014-02-21 10:48:35 +10:00
commit 7aa403df75
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58
docs/sources/installation/ubuntulinux.rst
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@ -261,6 +261,64 @@ incoming connections on the Docker port (default 4243):
.. _installmirrors:
Docker and local DNS server warnings
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Systems which are running Ubuntu or an Ubuntu derivative on the desktop will
use `127.0.0.1` as the default nameserver in `/etc/resolv.conf`. NetworkManager
sets up dnsmasq to use the real DNS servers of the connection and sets up
`nameserver 127.0.0.1` in `/etc/resolv.conf`.
When starting containers on these desktop machines, users will see a warning:
.. code-block:: bash
WARNING: Local (127.0.0.1) DNS resolver found in resolv.conf and containers can't use it. Using default external servers : [8.8.8.8 8.8.4.4]
This warning is shown because the containers can't use the local DNS nameserver
and Docker will default to using an external nameserver.
This can be worked around by specifying a DNS server to be used by the Docker
daemon for the containers:
.. code-block:: bash
sudo nano /etc/default/docker
---
# Add:
DOCKER_OPTS="-dns 8.8.8.8"
# 8.8.8.8 could be replaced with a local DNS server, such as 192.168.1.1
# multiple DNS servers can be specified: -dns 8.8.8.8 -dns 192.168.1.1
The Docker daemon has to be restarted:
.. code-block:: bash
sudo restart docker
.. warning:: If you're doing this on a laptop which connects to various networks, make sure to choose a public DNS server.
An alternative solution involves disabling dnsmasq in NetworkManager by
following these steps:
.. code-block:: bash
sudo nano /etc/NetworkManager/NetworkManager.conf
----
# Change:
dns=dnsmasq
# to
#dns=dnsmasq
NetworkManager and Docker need to be restarted afterwards:
.. code-block:: bash
sudo restart network-manager
sudo restart docker
.. warning:: This might make DNS resolution slower on some networks.
Mirrors
^^^^^^^