[TriLUG] Revisiting local dnsmasq DNS resolution
Seva Adari
oddissyus at gmail.com
Fri Nov 2 23:35:52 EDT 2012
Part of the issue could be the configuration of dnsmasq that I don't understand!
You stated before that making a localhost entry in /etc/resolv.conf made the
dig work. Does this mean the your dns service is working off your loopback
device and not the ethernet device? Can you check if there is a place in
dnsmasq configuration where you can set the interface on which you make
the dns to listen in on the incoming requests. If you could make such an entry,
then set it to the eth0's ip address (you may have to restart dnsmask) and
reflect that ip address in your nameserver in /etc/resolv.conf and see if that
is going to make a difference.
On Fri, Nov 2, 2012 at 5:03 PM, Brian Henning <bhenning at pineinst.com> wrote:
> Hi Seva,
>
> Thanks for your ongoing input. I will look at that dnsmasq bug soon.
>
> As far as /etc/resolv.conf, it only gets rewritten when my outside interface
> loses its lease for whatever reason. I had already added "nameserver
> 127.0.0.1" at the start of its nameserver list, which is what made host and
> dig start working. I've also already modified the
> /etc/sysconfig/network-scripts/ifcfg-eth0 script to make sure that change is
> preserved when DHCP is renewed.
>
> I looked in /etc/nsswitch.conf and didn't see a line that STARTS with "dns",
> but I did see this line:
>
> hosts: files dns
>
> Maybe that is what you were asking about?
>
> By the way:
> $ grep blueman /etc/hosts
> $
>
> so it's definitely not in there.
>
> Cheers,
> ~Brian
>
>
> -----Original Message-----
> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On Behalf
> Of Seva Adari
> Sent: Friday, November 02, 2012 4:46 PM
> To: Triangle Linux Users Group General Discussion
> Subject: Re: [TriLUG] Revisiting local dnsmasq DNS resolution
>
> Hi Brian,
>
> 1. See if the following has any helpful pointers for your case:
> https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/998712
>
> 2. You indicated that the /etc/resolv.conf is automatically setup
> for you by the DHCP. Can you check and make sure if it is
> adding the right nameserver ip address. If not, can you add
> it manually and see if you are able to resolve the hostname.
>
> 3. Can you also check and see what you have listed for dns in
> /etc/nsswitch.conf
>
> __
> Seva
>
> On Fri, Nov 2, 2012 at 12:54 PM, Brian Henning <bhenning at pineinst.com>
> wrote:
>> Hi Seva,
>>
>> dnsmasq is a DHCP and DNS server in one, so it is always able to resolve
>> hostnames for the machines to which it assigns leases (assuming the client
>> machine includes its hostname in the DHCPREQ packet, which seems to be the
>> case for most devices on my network). blueman has never had any entry in
>> any /etc/hosts file; the "hostname entry" is in the dhcp leases file
>> maintained by dnsmasq.
>>
>> Yes, I can do anything I want if I use the IP address directly; recall my
>> original statement that using:
>>
>> $ ssh `dig +short blueman`
>>
>> (where the backtick operator provides the output of 'dig +short blueman'
> to
>> ssh as a command-line argument)
>>
>> works just fine.
>>
>>
>> Cheers,
>> ~Brian
>>
>>
>> -----Original Message-----
>> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
> Behalf
>> Of Seva Adari
>> Sent: Thursday, November 01, 2012 1:23 PM
>> To: Triangle Linux Users Group General Discussion
>> Subject: Re: [TriLUG] Revisiting local dnsmasq DNS resolution
>>
>> If these machines are DHCP assigned then where is the hostname entry
>> made?
>>
>> I have not used dnsmasq, but for 'blueman' to resolve to ip address you
>> would have to either configure your dns system or make entry in
> /etc/hosts.
>> The fact that dig is resolving 'blueman' shows that you had your dns
> system
>> configured to resolve to '192.168.0.124'. Are you sure that your DHCP is
>> actually assigning '192.168.0.124' to 'blueman'.
>>
>> Can you ping or ssh directly to '192.168.0.124'?
>>
>> On Thu, Nov 1, 2012 at 1:01 PM, Brian Henning <bhenning at pineinst.com>
> wrote:
>>>> Did you check to see if you can resolve 'blueman' from other
>>>> programs, may be starting with ping.
>>>
>>> It seems that everybody EXCEPT host and dig fails to resolve blueman.
>>>
>>>> Is blueman part of your lan or is part of the search domain?
>>>
>>> blueman is a machine on the local network, which is assigned DHCP by
>>> dnsmasq. There's no domain suffix.
>>>
>>> It basically looks something like this:
>>>
>>> [ blueman ]
>>> 192.168.0.124
>>> |
>>> [lan]---- [other internal hosts]
>>> |
>>> [ mailwall ]
>>> 192.168.0.80
>>> <public_ip>
>>> |
>>> {{internet}}
>>>
>>> This is ONLY a problem on mailwall itself (where dnsmasq resides). All
>> the
>>> other hosts on the LAN can resolve local names just fine (they look to
>>> mailwall for DNS).
>>>
>>> On mailwall itself, as I've said, host and dig will succeed, but nobody
>> else
>>> will. I've tried ping, ssh, nmap, ftp, telnet... nobody knows who
> blueman
>>> is!
>>>
>>> ~B
>>>
>>>> On 11/1/2012 11:15 AM, Seva Adari wrote:
>>>>>
>>>>> Looks like 'short' is resolved but not 'blueman'.
>>>>> Do you know how 'short' is resolved? Via /etc/hosts or your dns?
>>>>>
>>>>> Try to use a fully qualified hostname and see if you are able
>>>>> to resolve your host, if you do then it may be related to your
>>>>> search domain.
>>>>> What do you have for "search" entry listed in /etc/resolv.conf?
>>>>>
>>>>> On Thu, Nov 1, 2012 at 10:28 AM, Brian Henning <bhenning at pineinst.com>
>>>>> wrote:
>>>>>>
>>>>>> Hi List,
>>>>>>
>>>>>> Not too long ago I started a short thread about the apparent failure
> of
>>>>>> dnsmasq to resolve local hostnames (things it knows about from its own
>>>>>> leases file) on the machine where it's actually running. The main
>> theme
>>>>>> of
>>>>>> responses seemed to be "make sure localhost is first in
>>>>>> /etc/resolv.conf".
>>>>>>
>>>>>> I made that change, but it still seems not to work completely as
>>>>>> expected.
>>>>>> dig and host will resolve names, but whatever mechanism is used
>>>>>> internally
>>>>>> by programs won't. What I'm trying to say is this:
>>>>>>
>>>>>> $ ssh blueman
>>>>>> ssh: blueman: name or service not known
>>>>>>
>>>>>> $ ssh `dig +short blueman`
>>>>>> brian at 192.168.0.124's password:
>>>>>>
>>>>>> Why would that be? What do I need to change to make "ssh blueman"
>> work?
>>>>>> Do
>>>>>> I just need to restart something?
>>>>>>
>>>>>> Many thanks for the advice and hand-holding. I don't know why this is
>>>>>> escaping me.
>>>>>>
>>>>>> Cheers,
>>>>>> ~Brian
>>>>>>
>>>>>> ------------------------------------------------------
>>>>>> Brian Henning, Software Engineer
>>>>>>
>>>>>> /\ Pine Research Instrumentation
>>>>>> //\\ 2741 Campus Walk Ave, Bldg 100
>>>>>> ///\\\ Durham, NC 27705
>>>>>> ////\\\\ USA
>>>>>> ||
>>>>>> || phone: 919.782.8320
>>>>>> fax: 919.782.8323
>>>>>> email: bhenning at pineinst.com
>>>>>> ------------------------------------------------------
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
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>>>>
>>>>
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