ubuntu desktop 18.04 networking dns server not added by NetworkManager

[urmajest]

Hello.

I have had a ubuntu desktop 14.04 with manual network configuration. I recently upgraded it to 18.04.
Upgrading to 18.04 has broken my DNS server configuration and I can temporary fix it by editing /etc/resolv.conf.
However, I want to know how to do it CORRECTLY. Can someone help me find the way?

First, I wanted to figure out where my manual network configuration is stored. (Yes, I have not used it for a long time.)
I found nothing in /etc/network/interfaces. I have no files in /etc/netplan.

obelle:etc > cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
obelle:etc > ls -a /etc/netplan
...

I tried to grep my ip address in /etc and found NetworkManager is having my manual network configurations

obelle:etc > sudo grep -H "111.222.198.39" -r *
NetworkManager/system-connections/Wired connection 1:address1=111.222.198.39/24,111.222.198.1
obelle:etc > sudo cat "NetworkManager/system-connections/Wired connection 1"
[connection]
id=Wired connection 1
uuid=0238a1e0-487a-48b6-9661-6bf71d8678fc
type=ethernet
permissions=
timestamp=1539753475


[ethernet]
mac-address=00:3E:E1:C8:65:C1
mac-address-blacklist=


[ipv4]
address1=111.222.198.39/24,111.222.198.1
dns=111.222.16.61;111.222.16.62;
dns-search=my.domain.com;
method=manual


[ipv6]
addr-gen-mode=eui64
dns-search=
method=auto

I edited IP prefix to 111.222 and search domain to my.domain.com for anonymity.
Yes NetworkManager has both DNS servers but they are never added to /etc/resolv.conf.

obelle:etc > cat resolv.conf
# 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
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.


nameserver 127.0.0.53
obelle:etc > systemd-resolve --status
Global
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test


Link 3 (eth1)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no


Link 2 (eth0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

It appears NetworkManager's DNS server configuration does not apply. How can I fix this?

[chili555]

I have no files in /etc/netplan

Is netplan installed?

sudo dpkg -s netplan.io | grep Status

What does this report?

ls -al /etc/resolv.conf
ps aux | grep systemd

[urmajest]

Thank you chili555,


It appears netplan is installed.
systemd-resolved appears to be running.

obelle:~ > sudo dpkg -s netplan.io | grep Status
Status: install ok installed
obelle:~ > ls -al /etc/resolv.conf
lrwxrwxrwx 1 root root 29  1월 25  2016 /etc/resolv.conf -> ../run/resolvconf/resolv.conf
obelle:~ > ps aux | grep systemd
root       330  0.0  0.1 134608 39336 ?        S<s  10월18   0:00 /lib/systemd/systemd-journald
root       358  0.0  0.0  46944  5212 ?        Ss   10월18   0:00 /lib/systemd/systemd-udevd
systemd+   690  0.0  0.0 146096  3280 ?        Ssl  10월18   0:11 /lib/systemd/systemd-timesyncd
systemd+   698  0.0  0.0  70612  5160 ?        Ss   10월18   0:09 /lib/systemd/systemd-resolved
root       873  0.0  0.0  70612  6100 ?        Ss   10월18   0:00 /lib/systemd/systemd-logind
message+   878  6.4  0.0  51364  5644 ?        Ss   10월18  78:20 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
gdm       1376  0.0  0.0  76860  8048 ?        Ss   10월18   0:00 /lib/systemd/systemd --user
gdm       1414  0.0  0.0  50272  4616 ?        Ss   10월18   0:00 /usr/bin/dbus-daemon --session --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
hwanjo    4181  0.1  0.0  76760  7768 ?        Ss   11:16   0:00 /lib/systemd/systemd --user
hwanjo    4307  0.0  0.0  16020  1092 pts/0    S+   11:16   0:00 grep --color=auto systemd

[chili555]

Let’s try a few repairs. First, we’ll recreate the missing netplan file:

cd /etc/netplan
sudo nano 01-network-manager-all.yaml

Add the following. Spacing, indentation, etc. are crucial and must be perfect.

# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

Proofread carefully, save and close the text editor. Now do:

sudo netplan generate
sudo netplan apply

Next, I believe that your /etc/resolv.conf is faulty. In your case, resolv.conf is not pointing to systemd as expected. Therefore, please remove and recreate the link:

sudo rm -f /etc/resolv.conf
ln -s /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf

Reboot and let us know if there is any improvement.

[urmajest]

Thank you chili555,

I did what you have suggested step by step and reboot. (To be perfect, 'ln -s' required sudo)

I have created the yaml file and let netplan generate and apply

obelle:~ > ls -l /etc/netplan
total 4
-rw-r--r-- 1 root root 104 10월 22 09:06 01-network-manager-all.yaml
obelle:~ > cat /etc/netplan/01-network-manager-all.yaml 
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

/etc/resolv.conf is now pointing to systemd's. However, dns server is not set.

obelle:~ > ls -l /etc/resolv.conf
lrwxrwxrwx 1 root root 37 10월 22 09:07 /etc/resolv.conf -> /run/systemd/resolve/stub-resolv.conf
obelle:~ > cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# 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 "systemd-resolve --status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must 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
obelle:~ > systemd-resolve --status
Global
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test


Link 3 (eth1)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no


Link 2 (eth0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

Well, my ip configuration is correctly set (according to NetworkManager's configuration) after reboot.
I believe there's no other subsystem that configures my IP address (as /etc/network/interfaces and /etc/netplan do not have my IP address setting)
My IP address configuration and DNS settings are correctly set after reboot on NetworkManager app and /etc/NetworkManager/system-connections/Wired connection 1.
It's strange that DNS server setting (and DNS search domain) is not applied somehow.

[chili555]

My IP address configuration and DNS settings are correctly set after reboot on NetworkManager app

Automatic (DHCP) or have you specified any settings?

May I see:

sudo NetworkManager --print-config

I suspect the 'dns=' line is faulty.

[urmajest]

Thank you chili555,

Automatic (DHCP) or have you specified any settings?

I have manual IP address and DNS server configuration. The following shows what NetworkManager GUI shows.

(I modified my IP prefix to 111.222)

obelle:etc > sudo cat "NetworkManager/system-connections/Wired connection 1"
[connection]
id=Wired connection 1
uuid=0238a1e0-487a-48b6-9661-6bf71d8678fc
type=ethernet
permissions=
timestamp=1539753475


[ethernet]
mac-address=00:3E:E1:C8:65:C1
mac-address-blacklist=


[ipv4]
address1=111.222.198.39/24,111.222.198.1
dns=111.222.16.61;111.222.16.62;
dns-search=my.domain.com;
method=manual


[ipv6]
addr-gen-mode=eui64
dns-search= method=auto

May I see:

sudo NetworkManager --print-config

I suspect the 'dns=' line is faulty.

obelle:~ > sudo NetworkManager --print-config
# NetworkManager configuration: /etc/NetworkManager/NetworkManager.conf (lib: 10-dns-resolved.conf, 20-connectivity-ubuntu.conf, no-mac-addr-change.conf) (etc: 10-globally-managed-devices.conf, default-wifi-powersave-on.conf)


[main]
# rc-manager=symlink
# auth-polkit=true
# dhcp=dhclient
dns=dnsmasq
plugins=ifupdown,keyfile,ofono
no-auto-default=00:3E:E1:C8:65:C1,


[connectivity]
uri=http://connectivity-check.ubuntu.com/


[ifupdown]
managed=false


[logging]
# backend=journal
# audit=true


[device-mac-addr-change-wifi]
match-device=driver:rtl8723bs,driver:rtl8189es,driver:r8188eu,driver:8188eu,driver:eagle_sdio,driver:wl
wifi.scan-rand-mac-address=no
wifi.cloned-mac-address=preserve
ethernet.cloned-mac-address=preserve


[connection]
wifi.powersave=3

I don't know if networkmanager --print-config should have my manual IP address configuration and DNS server setting.

Any suggestions?

[chili555]

Let's have a look at:

sudo service systemd-resolved status

Is it active?

If not, try:

sudo systemctl enable systemd-resolved.service
sudo service systemd-resolved start

Check:

ping -c3 8.8.8.8
ping -c3 www.ubuntu.com

[urmajest]

Thanks you chili555,

Now I understand how things are working and solved the problem.

So, the DNS server configuration (/etc/resolv.conf) is controlled by systemd-resolved at my system.
I have configured my DNS server setting at NetworkManager.
It appears that systemd-resolved overrides what NetworkManager configures.
I have solved my problem by disabling systemd-resolved.

sudo service systemd-resolved stop
sudo systemctl disable systemd-resolved
sudo rm -f /etc/resolv.conf
sudo service NetworkManager restart

Many thanks to chili555 for your kind guidance!