[Dnsmasq-discuss] using dnsmasq for dns/dhcp with minimal dynamic changes to dns

[Ben Cohen]

Hi sorry to dredge up a question from the archives -- but this got put on hold and I'm just now implementing it.

I'm trying to ensure that dns always has forward and reverse entries for my hosts with static ip mappings.  Here's the question I asked and the response:

On Mar 1, 2013, at 10:38 PM, Simon Kelley <simon at thekelleys.org.uk> wrote:

> On 01/03/13 04:04, Nathaniel Cohen wrote:
>> Hi -- I'm new to dnsmasq.  I've read through the docs but not yet
>> configured the service for my environment.  I'll be using dnsmasq to
>> manage dhcp and dns for a small network.
>> 
>> I've got a simple question but wasn't able to figure out the answer
>> from the docs.  I need all the locally managed dns names under the
>> purview of dnsmasq to be resolvable at all times -- regardless of the
>> state of the client dhcp transactions/nic.  Is there a good pattern
>> to do this without having to duplicate the host <-> ip address
>> mapping information in more than one place …?
>> 
>> eg: If I use a set of entries like this:
>> 
>> dhcp-host=xx:xx:xx:xx:xx:xx, somedns, 10.10.1.1,  12h
>> 
>> Will somedns always resolve to 10.10.1.1 (and the reverse resolution
>> from 10.10.1.1 to somedns) even if the dhcp client with that mac
>> address is offline and/or has never performed a dhcp request …?
> 
> No the DNS records will only exist whilst a valid DHCP lease exists. You can do what you want but you need to split the configuration into two, though you don't need to duplicate the mappings.
> 
> The dnsmasq.conf configuration becomes.
> 
> dhcp-host=xx:xx:xx:xx:xx:xx, somedns, 12h
> 
> 
> and then in /etc/hosts
> 
> 10.10.1.1   somedns
> 
> The /etc/hosts line will give you a permanent DNS entry, and the name will be looked up in the DNS which the DHCP lease is created and the address used for DHCP too.
> 
> 
> If you want to keep everything in one file, you can use
> 
> host-record=somedns, 10.10.1.1
> 
> in dnsmasq.conf
> 
> instead of /etc/hosts.

I want to use the host-record= mechanism you describe.  Here's an example from my configuration:

dhcp-host=00:15:62:ff:b4:6e, set:is_wap4410n, set:adm, wap4410n-crstateroom, 12h
host-record=wap4410n, 172.19.149.130

I'm changing a functional dnsmasq install.  When I restart dnsmasq with the above host-record line uncommented it dnsmasq completely hangs while starting …  Any ideas how to track this down?

Thanks,
Ben