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Adam K Dean
Adam K Dean

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Local DNS resolver found in resolv.conf and containers can't use it

I've been playing with Docker for part of a project, and came across this annoying but important message:

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]

The problem? /etc/resolv.conf has nameserver 127.0.0.1 (or nameserver 127.0.1.1) in it.

I worked out that Ubuntu 14.04 LTS uses a daemon called dnsmasq, which routes DNS traffic through to the DNS servers provided by DHCP.

While this works fine for Docker, that message is quite annoying.

I disabled dnsmasq in /etc/NetworkManager/NetworkManager.conf:

$ sudo nano /etc/NetworkManager/NetworkManager.conf

#dns=dnsmasq
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I then added the public Google DNS servers to /etc/dhcp/dhclient.conf:

$ sudo nano /etc/dhcp/dhclient.conf

prepend domain-name-servers 8.8.8.8,8.8.4.4;
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Then you just need to restart NetworkManager:

$ sudo restart network-manager
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And now you can start Docker containers without that pesky message!

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How to write a kickass README

Arguably the single most important piece of documentation for any open source project is the README. A good README not only informs people what the project does and who it is for but also how they use and contribute to it.

If you write a README without sufficient explanation of what your project does or how people can use it then it pretty much defeats the purpose of being open source as other developers are less likely to engage with or contribute towards it.