/var/run/dnsmasq/resolv.conf empty on boot

[Andrew Bayliss]

I have a machine that serves as a router, with an ADSL modem on one ethernet port, the rest of my network on the other, and using dnsmasq to provide DNS/DHCP to the network. In the past dnsmasq and ppp have happily co-existed, with dnsmasq reading the upstream DNS servers from /var/run/dnsmasq/resolv.conf. After upgrading to Oneiric, I'm finding that /var/run/dnsmasq/resolv.conf is always empty on boot. If I if{down,up} ppp0, the upstream servers are written to this file, dnsmasq picks them up and everything starts working.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: dnsmasq 2.57-1ubuntu1 [modified: etc/dnsmasq.conf]
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
ApportVersion: 1.23-0ubuntu3
Architecture: i386
Date: Sun Oct 16 21:00:24 2011
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
SourcePackage: dnsmasq
UpgradeStatus: Upgraded to oneiric on 2011-10-16 (0 days ago)
mtime.conffile..etc.dnsmasq.conf: 2011-10-16T20:16:02.720988

[Scott Moser (smoser)]

I suspect that this is related to bug 876458.

[Andrew Bayliss (abayliss)]

I initially thought it might be boot order related, but I'm not convinced. Restarting dnsmasq does not fix the problem, as /var/run/dnsmasq/resolv.conf is still empty. Taking my ppp0 interface down/up solves the problem as dnsmasq notices that the contents of /var/run/dnsmasq/resolv.conf has changed.

[Carl Davis (carl.davis)]

Andrew,

Can you please look at bug 862134 and determine if network-manager overwriting resolv.conf is causing your issues with dnsmasq?

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[Andrew Bayliss (abayliss)]

NetworkManager is not installed on this machine.

[Chad Kidder (cckidder)]

I can verify this on my 11.10 server using two ethernet networks. Network manager is not installed. Please see the attached configuration files.

[Chad Kidder (cckidder)]

A short term hack seems to be to change the location of the resolv.conf pointed to in the daemon script, /etc/init.d/dnsmasq.

I changed it to point to /etc/resolvconf/resolv.conf.d/original instead of /var/run/dnsmasq/resolv.conf and that seems to have worked around the problem.

From what I can tell, until the interface with DHCP is brought down then up, the resolvconf update script for dnsmasq is not getting the DNS servers given by DHCP.

[Chad Kidder (cckidder)]

It seems that my problem can be traced to putting a gateway line in my /etc/network/interfaces file for the static internal interface. That was causing routing problems as well. After removing the gateway line and restarting networking and dnsmasq I now have name servers in /var/run/dnsmasq/resolv.conf.

[Chad Kidder (cckidder)]

On further inspection, it did not solve the problem. restarting the networking along with the fix of the gateway solved the problem. To get it working reliably, I had to add:

ifdown eth1 && ifup eth1 into /etc/init.d/dnsmasq in the start section.

[Thomas Hood (jdthood)]

This may have been a bug in resolvconf, specifically #366967 et al. If so then it has been fixed in Precise. Please check.

[Andrew Bayliss (abayliss)]

Yes, this appears to have been fixed in Precise.