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David
Asked: 2013-03-05 14:37:35 +0800 CST

DNS lookups failing

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Gateway 192.168.122.1 runs dns, and the command dig @192.168.122.1 www.google.com returns valid ip addresses, so dns is working and reachable.

The command tracepath www.google.com returns gethostbyname2: Host name lookup failure.

The command tracepath 74.125.129.103 (www.google.com) yields valid results, so the default route is set up correctly.

The command route -n outputs:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.122.1   0.0.0.0         UG    100    0        0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 eth0

And the applicable portion of /etc/network/interfaces reads:

auto eth0
iface eth0 inet static
    address 192.168.122.5
    netmask 255.255.255.0
    broadcast 192.168.122.255
    gateway 192.168.122.1
    dns-servers 192.168.122.1

No firewalls are currently running.

I would think, given these settings, that tracepath www.google.com would contact 192.168.122.1 for dns information, which is verified to be working and reachable.

What should I do next to find out why the tracepath command returns gethostbyname2: Host name lookup failure?

Edit (more info)

/etc/resolv.conf is empty. Ubuntu 12.04 uses a new subsystem, resolvconf, that autogenerates resolv.conf data in /etc/resolvconf/resolv.conf.d/*.

/etc/resolvconf/resolv.conf.d/original contains:

nameserver 192.168.122.1

All other resolv.conf.d files (head and base)are empty.

/etc/nsswitch.conf contains:

    passwd:         compat
    group:          compat
    shadow:         compat

    hosts:          files dns
    networks:       files

    protocols:      db files
    services:       db files
    ethers:         db files
    rpc:            db files

    netgroup:       nis

/etc/hosts contains:

    127.0.0.1       localhost
    127.0.1.1       hostname

    # The following lines are desirable for IPv6 capable hosts
    ::1     ip6-localhost ip6-loopback
    fe00::0 ip6-localnet
    ff00::0 ip6-mcastprefix
    ff02::1 ip6-allnodes
    ff02::2 ip6-allrouters
ubuntu

2 Answers

  1. Best Answer

    I'm not very familiar with the resolv.conf.d version, but I believe you should put the lookup settings in /etc/resolv/resolv.conf.d/base instead of /etc/resolv/resolv.conf.d/original

    • 1

  2. The accepted answer, where the nameserver directive goes in the /etc/resolv/resolv.conf.d/base file is one way of managing the nameserver setting in ubuntu's new resolvconf subsystem, but there is also another way, which I had been attempting with my config.

    Nameservers can also be set in the /etc/network/interfaces file using the dns-nameservers directive.

    My problem was a typo! I had written dns-nameservers as "dns-servers".

    I've verified both the accepted answer and this answer to work.

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