No DNS Resolving on Ubuntu VM

Question

_{Friday, October 10, 2014 8:03 AM}

Hi,

Last night at around Oct  9 21:36:02 CEST (checked from my email /var/log/mail.err file), my VM has stopped getting any DNS resolution.

I'm running a Ubuntu VM.

curl "http://www.microsoft.com"

Returns: curl: (6) Could not resolve host: www.microsoft.com

curl "65.55.57.27" (ms ip) returns HTML and a web page.

Curl or anything cannot connect to any external machine, via dns names, using IP works fine.

I checked which NS I'm using, looking at /etc/resolv.conf:

# 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 100.79.132.140

If I change the IP to Googles DNS server, 8.8.8.8, all works fine. But, this needs to be fixed, so I can use MS internal DNS resolution.

I have not made any changes to cause this.

I have rebooted, and its not helped.

Can someone look into this please.

Thanks,

Rob Donovan.

All replies (5)

_{Tuesday, October 14, 2014 10:50 AM ✅Answered}

Hi Bob,

Thanks for your reply.

I have submitted this issue to the related team. Thanks for pointing it out.

Best regards,

Susie

_{Friday, October 10, 2014 8:40 AM}

For anyone else who might be getting this problem, these are the steps to make Ubuntu on Azure use Google Public DNS servers, if Azures DNS is down (as it is now).

1) Edit: /etc/resolvconf/resolv.conf.d/head

2) Add these lines under the comment at the top:

nameserver 8.8.8.8
nameserver 8.8.4.4

3) Rebuild the main conf file /etc/resolv.conf by running:

resolvconf  -u

All done, now your Ubuntu Azure machine will use Googles DNS first, and then try the local Azure one if Googles are down.

Once the Azure DNS has been fixed, its probably better to remove Googles, as I would have thought that Azures internal DNS would be quicker, but I have not tested that.

I also had to put my hostname into /etc/hosts/ as Google DNS does not have my local hostname obviously.

1) Edit: /etc/hosts

2) add your host name to the end of the line starting with 127.0.0.1 with a space between what is on that line and what you add.

HTHs,

Rob.

_{Friday, October 10, 2014 4:40 PM}

Well, as of about 20hrs into this, your Name Servers seem to have been fixed, as they are now responding.

I've swapped back to the internal NS, and its working

Would have been nice for support to have responded to this, earlier. Or at least your status page to have mentioned it. :(

I think you should review your support procedures, and its a bit ridiculous that your users cant get support of your product(s) when they go wrong.

_{Monday, October 13, 2014 5:19 AM}

Hi Rob,

Thanks for your feedback on this issue.

You are correct, it seems that there is no related report during 21:36 CEST (UTC+02:00) on 9th Oct on the Azure status page. Would you please tell us the region that VM belongs to? I apologize for the inconvenience for you and will report this to the related team and hope this won't happen again.

Best regards,

Susie

_{Monday, October 13, 2014 6:20 AM}

Hi,

Thanks for the reply.

The VM is in the 'South Central US' region.

Rob.