dnsmasq without dns functionality

Question

So, I'm trying to run dnsmasq as a PXE-only server. For this, I'm trying to disable dnsmasq's DNS functionality. I've put the following line in /etc/dnsmasq.conf:

port=0

However, when starting dnsmasq, it registers itself as DNS server in /etc/resolv.conf.

This is apparently done by /etc/init.d/dnsmasq. The file contains some code to disable this resolvconf behavior by having lo in $DNSMASQ_EXCEPT. But I can't figure out how I am suppose to put it in there (without editing the file).

I tried putting the following line in /etc/dnsmasq.conf:

except-interface=lo

But this doesn't help. Any ideas on how to solve this problem?

Update: I'm running Ubuntu Server 16.04.1.

Solution 1

Found it. Just add the following line to /etc/default/dnsmasq:

DNSMASQ_EXCEPT=lo

That's it.

Solution 2

Start it with -p0. You need to add this option to /etc/default/dnsmasq:

DNSMASQ_OPTS="-p0"

Info about port is from dnsmasq(8) man page

-p, --port=<port>
Listen on <port> instead of the standard DNS port (53). Setting this to zero 
completely disables DNS function, leaving only DHCP and/or TFTP.

Comments

[Gnimmelf]

Why would this work? Won't this just disable dnsmasq on the local interface, and still enable DNS on other interfaces?

[Sebastian Krysmanski]

@phihag This works because of port=0 (as stated in the question)