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David
Asked: 2024-07-09 04:32:33 +0800 CST

DNS Stopped resolving on upgrade to Ubuntu 23.10 and Ubuntu 24.04

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I just upgraded my Ubuntu 22.04 boxes to 23.10 and then to 24.04.

They stopped resolving DNS queries.

They are using systemd-resolved and resolvconf.

dns

2 Answers

  1. Best Answer

    If your /etc/resolv.conf file says your nameserver is 127.0.0.53 then you likely are using resolvconf and systemd-resolved.

    1. Make sure your systemd-resolved is installed:

    sudo apt install systemd-resolved

    (You might need to temporarily change your resolve.conf to use a well known dns server directly, like Google's, 8.8.8.8, or CloudFlare's 1.1.1.1, or another one)

    2. Make sure your configuration files have references to dns servers in them.

    For systems that use Debian style /etc/network/interfaces config files makes sure you have dns-nameservers set in the iface section. For example:

    auto  eth0
iface eth0 inet static
  address   1.2.3.4 
  netmask   255.255.255.0
  gateway   1.2.3.1
  dns-nameservers  8.8.8.8

    If you have a newer install you could instead be using Netplan. The config file is usually /etc/netplan/01-netcfg.yaml

    network:
  version: 2
  renderer: networkd
  ethernets:
    enp1s0:
      addresses:
        - 1.2.3.4/24
      routes:
        - on-link: true
          to: 0.0.0.0/0
          via: 1.2.3.1
      nameservers:
        addresses:
          - 8.8.8.8
          - 1.1.1.1

    3. Revert changes to resolv.conf

    Backout any changes made in step 1. to your resolv.conf file. That is, the line with nameserver should just be nameserver 127.0.0.53

    4. Restart services

    Restart networking systemctl restart systemd-networking

    Restart resolved systemctl restart systemd-resolved

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  2. Had a similar problem upgrading my 22.04 to 24.04. After rebooting, no DNS resolving (pings with IP addresses work though). Tried a similar approach to manually fix resolv.conf (indeed "broken" as well as reinstallation of systemd-resolved). Unfortunately, these steps didn't work for me.

    Was able to resolve by following approach:

    1. Perform "sudo apt update". Note the servers that your Ubuntu installation is trying to access.
    2. Use another computer or other device (I used my phone) to lookup the IP addresses of the servers that were identified above.
    3. Edit the /etc/hosts file to include those IP addresses. I used "sudo gedit /etc/hosts"
    4. Reboot your installation and log-in anew
    5. Now reinstall "resolvconf" with "sudo apt install --reinstall resolvconf". I noted that this also triggered an update of systemd-resolved.
    6. Reboot.
    7. After following these steps, the DNS resolution was operational. I further performed a "sudo apt update" and "sudo apt upgrade" as "insurance" that the packages were installed. I've rebooted and the systems seems to be functioning properly. Apologies in advance for my lack to technical details of the packages and specific edits - not my forte. But I believe the overall approach of manually putting in the required Ubuntu servers into the hosts file permits system utilities to do their job to fix the installation.
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