[lug] DNS issues with most recent Ubuntu updates?

Bear Giles bgiles at coyotesong.com
Mon Sep 11 11:09:32 MDT 2017


‚ÄčThis may or may not be related.

I've had trouble with a VirtualBox machine image. It has a bridged network
adapter but isn't showing up in the router's DHCP table. Logging into the
machine I see it's assigned itself an address in the 10.x.x.x range. That
defeats the purpose since the entire reason for using the bridged network
adapter on a VM image is to allow other systems so see it as a peer. (E.g.,
I'm using it to run a database or similar server. In some cases there are
docker images that allow us to do the same with a smaller footprint but
that isn't an option at the moment.)

I tracked it down to 'dnsmasq'. It's a lightweight DHCP and DNS caching
server. It's primarily designed for routers but Ubuntu has been bundling it
to perform DNS caching. That's not a problem - but setting it up as a DHCP
server is.

There are supposedly countless ways to deal with this. Tell it to use a
different address as the DHCP server. Disable the DHCP server. Disable
dnsmasq entirely. Remove the fricking dnsmasq package. Nothing worked - I
eventually tried using a static address but nuking the dnsmasq (and
indirectly the lxd) package seems to have fried something else. It looks
like I'm going to have to rebuild the image and figure out a different
solution.

To put it mildly I am not happy. Running ubuntu server within a virtualbox
machine in order to provide a service is not an uncommon use case. Caching
DNS lookups is fine but it shouldn't be acting as a DHCP server it that's
going to be causing problems. Let the people using it on routers enable
that explicitly.

On Thu, Aug 31, 2017 at 10:22 AM, Chip Atkinson <chip at pupman.com> wrote:

> If you can, try using a wired connection and see what happens.  I have an
> old laptop where the wireless network connection "drops" when I download
> too much data, say an ISO image.  If the problem goes away with the cable
> connection, it points to some sort of wireless issue.
>
>
>
>  On Thu, 31 Aug 2017, Quentin Hartman wrote:
>
> Ah, I missed the two locations detail. Same box multiple locations, or
>> multiple locations?
>> Q
>>
>> On Thu, Aug 31, 2017 at 9:35 AM, Bear Giles <bgiles at coyotesong.com>
>> wrote:
>>       Not nearly enough to trigger throttling, and that wouldn't explain
>> seeing the same behavior
>>       at home and in the office.
>>
>> On Thu, Aug 31, 2017 at 8:47 AM, Quentin Hartman <qhartman at gmail.com>
>> wrote:
>>       Sounds like you're getting throttled. Any idea how much data you've
>> pulled this
>>       month?
>> QH
>>
>> On Wed, Aug 30, 2017 at 3:18 PM, <stimits at comcast.net> wrote:
>>       I did an update on an Ubuntu 16.04 LTS machine with no issues, but
>> I'm using
>>       wired ethernet. Perhaps it is a WiFi issue or a router issue (FYI,
>> I am on
>>       comcast as well)? Don't know.
>>
>> ----- Original Message -----
>> From: Bear Giles <bgiles at coyotesong.com>
>> To: Boulder (Colorado) Linux Users Group -- General Mailing List
>> <lug at lug.boulder.co.us>
>> Sent: Wed, 30 Aug 2017 20:29:53 -0000 (UTC)
>> Subject: [lug] DNS issues with most recent Ubuntu updates?
>> Has anyone else noticed DNS issues with the most recent Ubuntu updates?
>> At first I
>> blamed it on a faulty router (and still do - this would not affect my
>> ability to
>> establish a wifi connection or ping a wired port) or on Comcastic!!
>> service but I'm
>> seeing it on my work network as well.
>> Behavior:
>> 1. Everything works fine for, oh, 10-20 minutes.
>> 2. Chromium starts to get "cannot resolve x.y.z address" errors.
>> 3. It looks like 'curl' also times out.
>> 4. Slack reports the network is down. Ditto the Chromium email alert.
>> However if I run 'dig' it quickly comes back with the correct address.
>> The really
>> weird thing is that if I copy the IP address into the chromium address
>> bar then I
>> still have a very long wait. I don't think I've actually waited long
>> enough to see if
>> I get a "cannot resolve address" error.
>> If I click on the wifi icon the wifi connection is restablished and
>> everything works
>> for 10 minutes.
>> This is zesty and I did an apt-get update/upgrade a few hours ago.
>> Thanks
>>
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