Temporary failure in name resolution on ubuntu server 22.04

bomberb17 · 08-13-2023, 02:16 AM

For some reason my RPi running ubuntu server 22.04 stopped resolving names.
e.g.

Code:

$ ping google.com
ping: google.com: Temporary failure in name resolution

Also:

Code:

$ resolvectl status
Global
       Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
     DNS Servers: 8.8.8.8 1.1.1.1

Link 2 (eth0)
Current Scopes: none
     Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

Link 3 (wlan0)
Current Scopes: DNS
     Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
   DNS Servers: 8.8.8.8 8.8.4.4 192.168.1.1

Link 4 (wg0)
Current Scopes: none
     Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

everything seems to be ok here..

Code:

$ cat /etc/resolv.conf
# This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
# Do not edit.
#
# This file might be symlinked as /etc/resolv.conf. If you're looking at
# /etc/resolv.conf and seeing this text, you have followed the symlink.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0 trust-ad
search .

But if I change the nameserver here the file is reset back to these values.

Code:

network:
    ethernets:
        eth0:
            dhcp4: true
            optional: true
    version: 2

    wifis:
        wlan0:
            link-local: [ ipv4 ]
            optional: true
            access-points:
                "ssid-name":
                    password: "password"
            dhcp4: true
            nameservers:
                addresses: [8.8.8.8, 8.8.4.4]

Code:

$ nslookup ubuntu.com
;; communications error to 127.0.0.53#53: timed out
;; communications error to 127.0.0.53#53: timed out
;; communications error to 127.0.0.53#53: timed out
;; no servers could be reached

I also tried

Code:

mv /etc/resolv.conf /etc/resolv.conf.bak

and:

Code:

$ nslookup ubuntu.com
;; UDP setup with ::1#53(::1) for ubuntu.com failed: address not available.
;; UDP setup with ::1#53(::1) for ubuntu.com failed: address not available.
;; UDP setup with ::1#53(::1) for ubuntu.com failed: address not available.
;; communications error to 127.0.0.1#53: connection refused
;; no servers could be reached

I also tried to open 43/tcp and 53/udp with ufw but that didn't help..

What else can I do?

bomberb17 · 08-13-2023, 03:14 AM

Hmm... resolved by creating a new resolv.conf file that is not symlinked.. Wonder why this symlink created problems, and why this needs to be a symlink in the first place..
Is it possible that my configuration will be broken again in future updates?

nini09 · 08-14-2023, 08:17 PM

Based on the output of nslookup ubuntu.com, the 'nameserver' IP address need to be changed to valid one in resolv.conf.

michaelk · 08-14-2023, 08:48 PM

https://wiki.archlinux.org/title/systemd-resolved

If you did not change any configuration settings the next time the system is booted/restarted the symlink will be recreated. Did you make any configuration changes or update the Pi recently that might correlate with DNS not working?
Did you add Google's DNS servers manually? If so where? Network Manager?