UPDATE #2: The next day after booting, I enabled and started systemd-resolved, which apparently reset it to its default configuration. Output of resolvectl status looks normal, and DNS now works with the stub resolver again, and life is good.
UPDATE: I stopped and disabled the systemd-resolved service, then added a nameserver to /etc/resolv.conf and everything works.
I rebooted, and /etc/resolv.conf was gone, so I enabled systemd-resolved, and started it, and DNS is working again.
============================================
DNS stopped working on Ubuntu 22.04. Real desktop system. In use for 3+ years. Normally connected to the Internet with WiFi, but tested with Ethernet cable to home router, and the same error occurs. Other devices, laptops and phones, use the home WiFi with no issues.
Specifying a DNS server using the "@" option to the "dig" command works, e.g. dig @1.1.1.1 askubuntu.com gives the expected result, but plain old dig askubuntu.com times out as shown below at the end of the nmcli output.
I cleared the DNS cache with sudo resolvectl flush-caches but it made no difference. Is there a way to reset the resolver service?
$ nmcli device
DEVICE TYPE STATE CONNECTION
wlp6s0 wifi connected logicprobe
ipv6leakintrf0 dummy connected pvpn-ipv6leak-protection
virbr0 bridge connected (externally) virbr0
p2p-dev-wlp6s0 wifi-p2p disconnected --
enp5s0 ethernet unavailable --
lo loopback unmanaged --
$ nmcli device show wlp6s0
GENERAL.DEVICE: wlp6s0
GENERAL.TYPE: wifi
GENERAL.HWADDR: 8C:C6:81:9C:CD:3B
GENERAL.MTU: 1500
GENERAL.STATE: 100 (connected)
GENERAL.CONNECTION: logicprobe
GENERAL.CON-PATH: /org/freedesktop/NetworkManager/ActiveConnection/7
IP4.ADDRESS[1]: 172.16.1.22/24
IP4.GATEWAY: 172.16.1.1
IP4.ROUTE[1]: dst = 172.16.1.0/24, nh = 0.0.0.0, mt = 600
IP4.ROUTE[2]: dst = 0.0.0.0/0, nh = 172.16.1.1, mt = 600
IP4.DNS[1]: 8.8.8.8
IP6.GATEWAY: --
$ nmcli device show wlp6s0
GENERAL.DEVICE: wlp6s0
GENERAL.TYPE: wifi
GENERAL.HWADDR: 8C:C6:81:9C:CD:3B
GENERAL.MTU: 1500
GENERAL.STATE: 100 (connected)
GENERAL.CONNECTION: logicprobe
GENERAL.CON-PATH: /org/freedesktop/NetworkManager/ActiveConnection/7
IP4.ADDRESS[1]: 172.16.1.22/24
IP4.GATEWAY: 172.16.1.1
IP4.ROUTE[1]: dst = 172.16.1.0/24, nh = 0.0.0.0, mt = 600
IP4.ROUTE[2]: dst = 0.0.0.0/0, nh = 172.16.1.1, mt = 600
IP4.DNS[1]: 8.8.8.8
IP6.GATEWAY: --
$ nmcli connection show id logicprobe
connection.id: logicprobe
connection.uuid: 9093c97c-ddf8-4743-bdb0-91fd3cd67dd0
connection.stable-id: --
connection.type: 802-11-wireless
connection.interface-name: wlp6s0
connection.autoconnect: yes
connection.autoconnect-priority: 0
connection.autoconnect-retries: -1 (default)
connection.multi-connect: 0 (default)
connection.auth-retries: -1
connection.timestamp: 1686104423
connection.read-only: no
connection.permissions: --
connection.zone: --
connection.master: --
connection.slave-type: --
connection.autoconnect-slaves: -1 (default)
connection.secondaries: --
connection.gateway-ping-timeout: 0
connection.metered: unknown
connection.lldp: default
connection.mdns: -1 (default)
connection.llmnr: -1 (default)
connection.dns-over-tls: -1 (default)
connection.wait-device-timeout: -1
802-11-wireless.ssid: logicprobe
802-11-wireless.mode: infrastructure
802-11-wireless.band: --
802-11-wireless.channel: 0
802-11-wireless.bssid: --
802-11-wireless.rate: 0
802-11-wireless.tx-power: 0
802-11-wireless.mac-address: --
802-11-wireless.cloned-mac-address: --
802-11-wireless.generate-mac-address-mask:--
802-11-wireless.mac-address-blacklist: --
802-11-wireless.mac-address-randomization:default
802-11-wireless.mtu: auto
802-11-wireless.seen-bssids: 94:A6:7E:F7:2B:E4
802-11-wireless.hidden: no
802-11-wireless.powersave: 0 (default)
802-11-wireless.wake-on-wlan: 0x1 (default)
802-11-wireless.ap-isolation: -1 (default)
802-11-wireless-security.key-mgmt: wpa-psk
802-11-wireless-security.wep-tx-keyidx: 0
802-11-wireless-security.auth-alg: --
802-11-wireless-security.proto: --
802-11-wireless-security.pairwise: --
802-11-wireless-security.group: --
802-11-wireless-security.pmf: 0 (default)
802-11-wireless-security.leap-username: --
802-11-wireless-security.wep-key0: <hidden>
802-11-wireless-security.wep-key1: <hidden>
802-11-wireless-security.wep-key2: <hidden>
802-11-wireless-security.wep-key3: <hidden>
802-11-wireless-security.wep-key-flags: 0 (none)
802-11-wireless-security.wep-key-type: unknown
802-11-wireless-security.psk: <hidden>
802-11-wireless-security.psk-flags: 0 (none)
802-11-wireless-security.leap-password: <hidden>
802-11-wireless-security.leap-password-flags:0 (none)
802-11-wireless-security.wps-method: 0x0 (default)
802-11-wireless-security.fils: 0 (default)
ipv4.method: auto
ipv4.dns: --
ipv4.dns-search: --
ipv4.dns-options: --
ipv4.dns-priority: 0
ipv4.addresses: --
ipv4.gateway: --
ipv4.routes: --
ipv4.route-metric: -1
ipv4.route-table: 0 (unspec)
ipv4.routing-rules: --
ipv4.ignore-auto-routes: no
ipv4.ignore-auto-dns: no
ipv4.dhcp-client-id: --
ipv4.dhcp-iaid: --
ipv4.dhcp-timeout: 0 (default)
ipv4.dhcp-send-hostname: yes
ipv4.dhcp-hostname: --
ipv4.dhcp-fqdn: --
ipv4.dhcp-hostname-flags: 0x0 (none)
ipv4.never-default: no
ipv4.may-fail: yes
ipv4.required-timeout: -1 (default)
ipv4.dad-timeout: -1 (default)
ipv4.dhcp-vendor-class-identifier: --
ipv4.dhcp-reject-servers: --
ipv6.method: disabled
ipv6.dns: --
ipv6.dns-search: --
ipv6.dns-options: --
ipv6.dns-priority: 0
ipv6.addresses: --
ipv6.gateway: --
ipv6.routes: --
ipv6.route-metric: -1
ipv6.route-table: 0 (unspec)
ipv6.routing-rules: --
ipv6.ignore-auto-routes: no
ipv6.ignore-auto-dns: no
ipv6.never-default: no
ipv6.may-fail: yes
ipv6.required-timeout: -1 (default)
ipv6.ip6-privacy: -1 (unknown)
ipv6.addr-gen-mode: stable-privacy
ipv6.ra-timeout: 0 (default)
ipv6.dhcp-duid: --
ipv6.dhcp-iaid: --
ipv6.dhcp-timeout: 0 (default)
ipv6.dhcp-send-hostname: yes
ipv6.dhcp-hostname: --
ipv6.dhcp-hostname-flags: 0x0 (none)
ipv6.token: --
proxy.method: none
proxy.browser-only: no
proxy.pac-url: --
proxy.pac-script: --
GENERAL.NAME: logicprobe
GENERAL.UUID: 9093c97c-ddf8-4743-bdb0-91fd3cd67dd0
GENERAL.DEVICES: wlp6s0
GENERAL.IP-IFACE: wlp6s0
GENERAL.STATE: activated
GENERAL.DEFAULT: yes
GENERAL.DEFAULT6: no
GENERAL.SPEC-OBJECT: /org/freedesktop/NetworkManager/AccessPoint/5
GENERAL.VPN: no
GENERAL.DBUS-PATH: /org/freedesktop/NetworkManager/ActiveConnection/7
GENERAL.CON-PATH: /org/freedesktop/NetworkManager/Settings/2
GENERAL.ZONE: --
GENERAL.MASTER-PATH: --
IP4.ADDRESS[1]: 172.16.1.22/24
IP4.GATEWAY: 172.16.1.1
IP4.ROUTE[1]: dst = 172.16.1.0/24, nh = 0.0.0.0, mt = 600
IP4.ROUTE[2]: dst = 0.0.0.0/0, nh = 172.16.1.1, mt = 600
IP4.DNS[1]: 8.8.8.8
DHCP4.OPTION[1]: dhcp_lease_time = 600
DHCP4.OPTION[2]: dhcp_server_identifier = 172.16.1.1
DHCP4.OPTION[3]: domain_name_servers = 172.16.1.1 192.168.1.1
DHCP4.OPTION[4]: expiry = 1686104901
DHCP4.OPTION[5]: ip_address = 172.16.1.22
DHCP4.OPTION[6]: next_server = 172.16.1.1
DHCP4.OPTION[7]: requested_broadcast_address = 1
DHCP4.OPTION[8]: requested_domain_name = 1
DHCP4.OPTION[9]: requested_domain_name_servers = 1
DHCP4.OPTION[10]: requested_domain_search = 1
DHCP4.OPTION[11]: requested_host_name = 1
DHCP4.OPTION[12]: requested_interface_mtu = 1
DHCP4.OPTION[13]: requested_ms_classless_static_routes = 1
DHCP4.OPTION[14]: requested_nis_domain = 1
DHCP4.OPTION[15]: requested_nis_servers = 1
DHCP4.OPTION[16]: requested_ntp_servers = 1
DHCP4.OPTION[17]: requested_rfc3442_classless_static_routes = 1
DHCP4.OPTION[18]: requested_root_path = 1
DHCP4.OPTION[19]: requested_routers = 1
DHCP4.OPTION[20]: requested_static_routes = 1
DHCP4.OPTION[21]: requested_subnet_mask = 1
DHCP4.OPTION[22]: requested_time_offset = 1
DHCP4.OPTION[23]: requested_wpad = 1
DHCP4.OPTION[24]: routers = 172.16.1.1
DHCP4.OPTION[25]: subnet_mask = 255.255.255.0
IP6.GATEWAY: --
$ dig @172.16.1.1 askubuntu.com
; <<>> DiG 9.18.12-0ubuntu0.22.04.1-Ubuntu <<>> @172.16.1.1 askubuntu.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52124
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;askubuntu.com. IN A
;; ANSWER SECTION:
askubuntu.com. 30 IN A 151.101.129.69
askubuntu.com. 30 IN A 151.101.65.69
askubuntu.com. 30 IN A 151.101.193.69
askubuntu.com. 30 IN A 151.101.1.69
;; Query time: 24 msec
;; SERVER: 172.16.1.1#53(172.16.1.1) (UDP)
;; WHEN: Tue Jun 06 21:20:06 CDT 2023
;; MSG SIZE rcvd: 95
$ dig askubuntu.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
; <<>> DiG 9.18.12-0ubuntu0.22.04.1-Ubuntu <<>> askubuntu.com
;; global options: +cmd
;; no servers could be reached
08-Jun-2023 added output of various commands
$ ip route
default via 172.16.1.1 dev wlp6s0 proto dhcp metric 600
169.254.0.0/16 dev virbr0 scope link metric 1000 linkdown
172.16.1.0/24 dev wlp6s0 proto kernel scope link src 172.16.1.22 metric 600
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown
$ resolvectl
Global
Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: foreign
Link 2 (enp5s0)
Current Scopes: none
Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Link 3 (wlp6s0)
Current Scopes: none
Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Link 4 (ipv6leakintrf0)
Current Scopes: DNS
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: ::1
DNS Servers: ::1
DNS Domain: ~.
Link 5 (virbr0)
Current Scopes: none
Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
$ ls -l /etc/resolv.conf
lrwxrwxrwx 1 root root 29 Jun 6 21:40 /etc/resolv.conf -> ../run/resolvconf/resolv.conf
$ systemctl --no-pager status systemd-resolved
● systemd-resolved.service - Network Name Resolution
Loaded: loaded (/lib/systemd/system/systemd-resolved.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2023-06-08 10:55:34 CDT; 27min ago
Docs: man:systemd-resolved.service(8)
man:org.freedesktop.resolve1(5)
https://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-managers
https://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients
Main PID: 1361 (systemd-resolve)
Status: "Processing requests..."
Tasks: 1 (limit: 76889)
Memory: 8.8M
CPU: 239ms
CGroup: /system.slice/systemd-resolved.service
└─1361 /lib/systemd/systemd-resolved
Jun 08 11:20:57 darkroom systemd-resolved[1361]: Using degraded feature set UDP instead of TCP for DNS server ::1.
Jun 08 11:21:08 darkroom systemd-resolved[1361]: Using degraded feature set TCP instead of UDP for DNS server ::1.
Jun 08 11:21:27 darkroom systemd-resolved[1361]: Using degraded feature set UDP instead of TCP for DNS server ::1.
Jun 08 11:21:43 darkroom systemd-resolved[1361]: Using degraded feature set TCP instead of UDP for DNS server ::1.
Jun 08 11:21:43 darkroom systemd-resolved[1361]: Using degraded feature set UDP instead of TCP for DNS server ::1.
Jun 08 11:21:59 darkroom systemd-resolved[1361]: Using degraded feature set TCP instead of UDP for DNS server ::1.
Jun 08 11:21:59 darkroom systemd-resolved[1361]: Using degraded feature set UDP instead of TCP for DNS server ::1.
Jun 08 11:22:14 darkroom systemd-resolved[1361]: Using degraded feature set TCP instead of UDP for DNS server ::1.
Jun 08 11:22:14 darkroom systemd-resolved[1361]: Using degraded feature set UDP instead of TCP for DNS server ::1.
Jun 08 11:22:30 darkroom systemd-resolved[1361]: Using degraded feature set TCP instead of UDP for DNS server ::1.
$ sudo netstat -lntup
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 1361/systemd-resolv
tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 2623/smbd
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 2623/smbd
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1647/sshd: /usr/sbi
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1570/cupsd
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 1915/dnsmasq
tcp6 0 0 :::445 :::* LISTEN 2623/smbd
tcp6 0 0 :::139 :::* LISTEN 2623/smbd
tcp6 0 0 :::22 :::* LISTEN 1647/sshd: /usr/sbi
tcp6 0 0 ::1:631 :::* LISTEN 1570/cupsd
udp 0 0 192.168.122.1:53 0.0.0.0:* 1915/dnsmasq
udp 0 0 127.0.0.53:53 0.0.0.0:* 1361/systemd-resolv
udp 0 0 0.0.0.0:67 0.0.0.0:* 1915/dnsmasq
udp 0 0 172.16.1.255:137 0.0.0.0:* 2561/nmbd
udp 0 0 172.16.1.22:137 0.0.0.0:* 2561/nmbd
udp 0 0 192.168.122.255:137 0.0.0.0:* 2561/nmbd
udp 0 0 192.168.122.1:137 0.0.0.0:* 2561/nmbd
udp 0 0 0.0.0.0:137 0.0.0.0:* 2561/nmbd
udp 0 0 172.16.1.255:138 0.0.0.0:* 2561/nmbd
udp 0 0 172.16.1.22:138 0.0.0.0:* 2561/nmbd
udp 0 0 192.168.122.255:138 0.0.0.0:* 2561/nmbd
udp 0 0 192.168.122.1:138 0.0.0.0:* 2561/nmbd
udp 0 0 0.0.0.0:138 0.0.0.0:* 2561/nmbd
udp 0 0 127.0.0.1:323 0.0.0.0:* 1603/chronyd
udp 0 0 0.0.0.0:631 0.0.0.0:* 2560/cups-browsed
udp 0 0 0.0.0.0:33469 0.0.0.0:* 1398/avahi-daemon:
udp 0 0 0.0.0.0:5353 0.0.0.0:* 1398/avahi-daemon:
udp6 0 0 :::47323 :::* 1398/avahi-daemon:
udp6 0 0 ::1:323 :::* 1603/chronyd
udp6 0 0 :::5353 :::* 1398/avahi-daemon:
$ systemd-resolve google.com
systemd-resolve: command not found
$ resolvectl query google.com
google.com: resolve call failed: All attempts to contact name servers or networks failed
