NetworkManager fails to make DHCP-supplied nameserver addresses available

[Jane Atkinson]

On occasion, network manager doesn't find/assign a DNS server. This is with an up-to-date Precise install, and on this occasion when ISO testing.

I doubt that it has to do with hardware, because it's happened on two completely different machines (Asus EeePC 900 with Atheros L2 chip and a desktop machine with r8169).

When this happens, the computer is assigned an IP number, an internet connection exists and I can ping various websites plus my router by using the IP number. Website names of course don't get resolved.

The problem is solved (in the short term) by entering "sudo dhclient" in a terminal.

~$ sudo dhclient
RTNETLINK answers: File exists

Before issuing this command, /etc/resolv.conf reads:

# 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 127.0.0.1
search lan

After issuing the command, /etc/resolv.conf reads:

# 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 192.168.1.254
nameserver 127.0.0.1
search lan

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: network-manager 0.9.3.995+git201203152001.04b2a74-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-20.32-generic-pae 3.2.12
Uname: Linux 3.2.0-20-generic-pae i686
ApportVersion: 1.95-0ubuntu1
Architecture: i386
CRDA: Error: [Errno 2] No such file or directory
Date: Sun Mar 25 01:51:16 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120324.1)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 LANGUAGE=en_NZ:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
RfKill:

SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/964288

[Mathieu Trudel-Lapierre (cyphermox)]

DNS servers are provided by dhclient via NetworkManager, and NetworkManager is responsible for starting dnsmasq and giving it the DNS information. The fact that 127.0.0.1 is the only thing in /etc/resolv.conf is indicative that dnsmasq should be taking over DNS resolution.

Can you please attach /run/nm-dns-dnsmasq.conf to this bug report, and verify that dnsmasq is indeed running when you notice this issue?

[Rohith Babu PS (rohithbab)]

Edit the file /etc/NetworkManager/NetworkManager.conf.
and comment the line dns=dnsmasq and restart the network manager.

[Thomas Hood (jdthood)]

@Jane:
Can you please attach /run/nm-dns-dnsmasq.conf to this bug report, and the output of the command "ps -elf|grep dnsmasq"?

[Thomas Hood (jdthood)]

The syslog seems to indicate that the NM-controlled dnsmasq does not start.

[Jane Atkinson (irihapeti)]

@Thomas Hood
I haven't seen this error for many weeks now. Do you still want the files?

[Thomas Hood (jdthood)]

@Jane: If you experience the problem again, please post the requested information here so we can investigate the cause with you.