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Ubuntu Desktop 12.04 uses dnsmasq to perform DNS lookups, but it is not configured to cache these results. (I have checked this by using dig to resolve names and I do not see a large improvement in the response time after the first lookup.) How do I configure the NetworkManager-controlled dnsmasq to cache the results of DNS lookups?

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3 Answers

I didn't want to upgrade from 12.04, but still wanted dnsmasq managed by NetworkManager with caching enabled, but as the other answer said, --cache-size=0 is hard-coded and can't be changed with configuration.

So what I ended up doing was the following, as root:

mv /usr/sbin/dnsmasq /usr/sbin/dnsmasq.real

and then creating a new file, /usr/sbin/dnsmasq with the following content:

#!/bin/bash
args=$(echo "$@" | sed 's/--cache-size=0/--cache-size=1000/')
/usr/sbin/dnsmasq.real $args

make sure you chmod +x /usr/sbin/dnsmasq, and change the cache-size from 1000 to whatever you want, enjoy your LTS release with a DNS cache!

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In Ubuntu 12.10 you can enable the cache of the NetworkManager-controlled dnsmasq instance by putting the line

cache-size=1000

(with your preferred number of names instead of 1000) in a new file in /etc/NetworkManager/dnsmasq.d/. To activate this change you must then do

sudo stop network-manager
sudo killall dnsmasq
sudo start network-manager

or reboot.

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in 12.04 dnsmasq is started by NetworkManager with hard-coded (i.e. not configurable) parameter --cache-size=0.

manpages for dnsmasq says setting cache-size to zero disables caching. If you want to enable caching, you will probably have to disable the dnsmasq-plugin for NetworkManager to prevent NetworkManager from starting dnsmasq and start your own instance of dnsmasq with cache-size greater then zero.

here you can read how to disable dnsmasq-plugin for NetworkManager: http://askubuntu.com/a/131422/71057

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