Remove EC2's entry from resolv.conf

amazon-ec2 debian resolve
Takuya Matsuyama picture Takuya Matsuyama · Jun 7, 2014 · Viewed 20k times · Source

I have private DNS servers and I want to write them to resolv.conf with resolvconf on Debian on AWS/EC2. There is a problem in the order of nameserver entries. In my resolv.conf, EC2's default nameserver is always written at first line like so:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#    DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 172.16.0.23
nameserver 10.0.1.185
nameserver 10.100.0.130
search ap-northeast-1.compute.internal

172.16.0.23 is EC2's default nameserver and others are mine.

How to remove EC2 entry? Or, how to move EC2 entry to third?

Here I have an interface file:

% ls -l /etc/resolvconf/run/interface/
-rw-r--r-- 1 root root  62 Jun  7 23:35 eth0

It seems that the file eth0 is automatically generated by dhcp so can't remove it permanently.

% cat /etc/resolvconf/run/interface/eth0
search ap-northeast-1.compute.internal
nameserver 172.16.0.23

My private DNS entry is here:

% cat /etc/resolvconf/resolv.conf.d/base
nameserver 10.0.1.185
nameserver 10.100.0.130

Please help.

Answer

xolox picture xolox · Oct 23, 2014

I think I just solved a very similar problem. I was bothered by Amazon EC2's crappy internal DNS servers so I wanted to run a local caching dnsmasq daemon and use that in /etc/resolv.conf. At first I just did echo nameserver 127.0.0.1 > /etc/resolv.conf but then I realized that my change would eventually be overwritten by the DHCP client after a reboot or DHCP lease refresh.

What I've now done instead is to edit /etc/dhcp3/dhclient.conf and uncomment the line prepend domain-name-servers 127.0.0.1;. You should be able to use the prepend directive in a very similar way.

Update: These instructions are based on Ubuntu Linux but I imagine the general concept applies on other systems as well, even other DHCP clients must have similar configuration options.

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