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Thread: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

  1. #1
    Join Date
    Dec 2017
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    33

    18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    I am wondering if I can get some tips on fixing my dns resolution for my 18.04 server machine. I use this machine as an OpenVPN server and a Samba file server, in addition to using it for light web browsing as a desktop. DNS resolution is neither successful from the Desktop interface nor from my OpenVPN remote client.


    I have been attempting to troubleshoot for several days with no success, and I see that many others have had issues with 18.04’s DNS. I am hoping to get the original bug repaired (no reverting to broken DNS resolution on every reboot) and to also access the outside Internet from both my remote OpenVPN client and the web browser on the home machine (in my house).


    I’m relatively novice to running a linux system, only starting with this Ubuntu server less than one year ago.


    I can ping 8.8.8.8 successfully, but not google.com.


    Code:
    “ping google.com
    ping: google.com: Name or service not known”
    I am pasting below some of my various settings.


    -----------------------------------------------------------------------


    Code:
     $ cat /etc/netplan/01-netcfg.yaml
    # This file describes the network interfaces available on your system
    # For more information, see netplan(5).
    network:
      version: 2
      renderer: networkd
      ethernets:
        enp2s0:
          dhcp4: true

    -----------------------------------------------------------------------


    Code:
    cat /etc/systemd/resolved.conf
    [Resolve]
    DNS=192.168.1.1
    #FallbackDNS=
    #Domains=
    #LLMNR=no
    #MulticastDNS=no
    #DNSSEC=no
    #Cache=yes
    #DNSStublistener=yes
    DNSStubHandler=no

    -----------------------------------------------------------------------


    Code:
    cat /etc/network/interfaces
    # The loopback network interface
    auto lo eth0
    iface lo inet loopback
    
    
    # The primary network interface
    auto eth0
    iface eth0 inet dhcp

    -----------------------------------------------------------------------


    Code:
    cat /etc/resolvconf/resolv.conf.d/head
    # 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 8.8.8.8
    -----------------------------------------------------------------------


    Code:
    cat /etc/dnsmasq.d/lxd
    # Tell any system-wide dnsmasq instance to make sure to bind to interfaces
    # instead of listening on 0.0.0.0
    # WARNING: changes to this file will get lost if lxd is removed.
    bind-interfaces
    except-interface=lxdbr0
    -----------------------------------------------------------------------


    Code:
    cat /etc/dnsmasq.d-available/lxd
    # Tell any system-wide dnsmasq instance to make sure to bind to interfaces
    # instead of listening on 0.0.0.0
    # WARNING: changes to this file will get lost if lxd is removed.
    bind-interfaces
    except-interface=lxdbr0

    -----------------------------------------------------------------------


    I would appreciate any tips and advice - as I’ve been trying to troubleshot both from similar threads on this forum, and others - for nearly a week now with no success.
    Last edited by CharlesA; September 3rd, 2018 at 02:28 AM. Reason: added code tags

  2. #2
    Join Date
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    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    First, let's see if you can reach Google's server at all. Try

    Code:
    host ubuntuforums.org 8.8.8.8
    You should see

    Code:
    $ host ubuntuforums.org 8.8.8.8
    Using domain server:
    Name: 8.8.8.8
    Address: 8.8.8.8#53
    Aliases: 
    
    ubuntuforums.org has address 91.189.94.16
    Do you?
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

  3. #3
    Join Date
    Dec 2017
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    33

    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    Hi SeijiSensei,

    Yes, appears so. I get the following:

    Code:
    host ubuntuforums.org 8.8.8.8
    Using domain server:
    Name: 8.8.8.8
    Address: 8.8.8.8#53
    Aliases: 
    
    
    ubuntuforums.org has address 91.189.94.16
    Last edited by CharlesA; September 3rd, 2018 at 02:29 AM. Reason: code tags

  4. #4
    Join Date
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    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    What if you use 8.8.8.8 here?
    cat /etc/systemd/resolved.conf
    Code:
    [Resolve]
    DNS=192.168.1.1
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

  5. #5
    Join Date
    Dec 2017
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    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    No dice it seems. Not just yet.

  6. #6
    Join Date
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    Distro
    Ubuntu 18.04 Bionic Beaver

    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    1. /etc/network/interfaces should be irrelevant now if you are using netplan, right?

    2. I see in netplan that you are using dhcp. That opens further questions:
    2a. Have you tried with static setup in netplan (static IP, DNS)? Servers should have static setup anyway, not relying on dhcp.
    2b. How come ../resolv.conf.d/head has 8.8.8.8 inside if using dhcp? Does your dhcp server transmit 8.8.8.8 as primary dns? Because you also have 192.168.1.1 in resolved.conf.
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 18.04 LTS 64bit

  7. #7
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    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    Quote Originally Posted by darkod View Post
    1. /etc/network/interfaces should be irrelevant now if you are using netplan, right?

    2. I see in netplan that you are using dhcp. That opens further questions:
    2a. Have you tried with static setup in netplan (static IP, DNS)? Servers should have static setup anyway, not relying on dhcp.
    2b. How come ../resolv.conf.d/head has 8.8.8.8 inside if using dhcp? Does your dhcp server transmit 8.8.8.8 as primary dns? Because you also have 192.168.1.1 in resolved.conf.

    Hi Darkod -

    I'm sure I've made a couple settings worse in trying my own haphazard troubleshooting this past week.

    For 2a - I will attempt to set up static DNS. To my knowledge this server (from a 16.04 install and later upgraded, has always been on DHCP - perhaps due to my own lack of technical acuity in running a private server).

    2b - I went back and rechecked - my /etc/resolvconf/resolv.conf.d/head now only shows the following

    Code:
    # 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
    ...I may have already changed that back after realizing it was a faulty setting.
    Last edited by ericbowers; September 3rd, 2018 at 07:10 PM.

  8. #8
    Join Date
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    Distro
    Ubuntu 18.04 Bionic Beaver

    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    Can you post the output of the following (I saw dnsmasq mentioned so we should know if it's installed):
    Code:
    apt-cache policy dnsmasq
    sudo netstat -plunt | grep 53
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 18.04 LTS 64bit

  9. #9
    Join Date
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    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    Quote Originally Posted by darkod View Post
    Can you post the output of the following (I saw dnsmasq mentioned so we should know if it's installed):
    Code:
    apt-cache policy dnsmasq
    sudo netstat -plunt | grep 53
    darkod - I see the following:

    Code:
    $ apt-cache policy dnsmasq
    dnsmasq:
      Installed: (none)
      Candidate: 2.79-1
      Version table:
         2.79-1 500
            500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
            500 http://us.archive.ubuntu.com/ubuntu bionic/universe i386 Packages
    and...

    Code:
    $ sudo netstat -plunt | grep 53
    [sudo] password for X?X?: 
    tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      1822/systemd-resolv 
    udp     6912      0 0.0.0.0:5353            0.0.0.0:*                           1303/avahi-daemon:  
    udp        0      0 127.0.0.53:53           0.0.0.0:*                           1822/systemd-resolv 
    udp6   25856      0 :::5353                 :::*                                1303/avahi-daemon:

  10. #10
    Join Date
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    Distro
    Ubuntu 18.04 Bionic Beaver

    Re: 18.04.1 Server all DNS resolution broken, no luck troubleshooting so far

    So dnsmasq is not installed, that is OK. And there seems to be something listening on port 53 but I can't figure out if that's local resolvconf process or not (don't have a 18.04 yet to try compare).

    Did you have opportunity to set up static IP in netplan and check how it goes? I would start from there... Don't forget when saying static IP we actually mean the rest of networking parameters that are necessary (netmask, gateway, dns server...).
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 18.04 LTS 64bit

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