[Bug 1710410] Re: Must run systemd-resolve --status before DNS resolving is operative

[Dimitri John Ledkov]

** Description changed:

+ [Impact]
+ systemd-resolved is not enabled by default, therefore relies on dbus activation to become active and operatable and update resolvconf with resolved stub resolver
+ 
+ [Fix]
+ Enable systemd-resolved in the src:systemd package by default, even when libnss-resolve is not installed
+ 
+ [Regression Potential]
+ Minimal, simply the service is now started earlier in the boot, as part of the multi-user.targer, rather than awaiting for dbus activation from command line tool or the nss-resolved module.
+ 
+ [Testcase]
+ Debootstrap minimal zesty, without libnss-resolve package installed, boot and check that 127.0.0.53 is present in /etc/resolv.conf and that systemd-resolved.service is running
+ 
  Context: fresh install of zesty via
  
  debootstrap --include=nano,dbus,iputils-ping,iproute2 zesty zesty1
  http://fr.archive.ubuntu.com/ubuntu
  
  ran via asystemd-nspawn with a static IP
  
  1. Upon first connexion, a ping fails:
  
  root at zesty1:~# ping google.com
  ping: google.com: Temporary failure in name resolution
  
  2. The content of /etc/resolv.conf:
  
  root at zesty1:~# cat /etc/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.
  
  3. When running systemd-resolve --status:
  
  root at zesty1:~# systemd-resolve --status
  Global
-          DNS Servers: 8.8.8.8
-                       8.8.4.4
-                       2001:4860:4860::8888
-                       2001:4860:4860::8844
-           DNSSEC NTA: 10.in-addr.arpa
-                       16.172.in-addr.arpa
-                       168.192.in-addr.arpa
+          DNS Servers: 8.8.8.8
+                       8.8.4.4
+                       2001:4860:4860::8888
+                       2001:4860:4860::8844
+           DNSSEC NTA: 10.in-addr.arpa
+                       16.172.in-addr.arpa
+                       168.192.in-addr.arpa
  (...)
  
  4. After running this command the resolution is miraculously restored:
  
  root at zesty1:~# ping google.com
  PING google.com (172.217.22.142) 56(84) bytes of data.
  64 bytes from 172.217.22.142 (172.217.22.142): icmp_seq=1 ttl=53 time=2.62 ms
  64 bytes from 172.217.22.142 (172.217.22.142): icmp_seq=2 ttl=53 time=1.93 ms

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https://bugs.launchpad.net/bugs/1710410

Title:
  Must run systemd-resolve --status before DNS resolving is operative

Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Zesty:
  In Progress
Status in systemd source package in Artful:
  Fix Released

Bug description:
  [Impact]
  systemd-resolved is not enabled by default, therefore relies on dbus activation to become active and operatable and update resolvconf with resolved stub resolver

  [Fix]
  Enable systemd-resolved in the src:systemd package by default, even when libnss-resolve is not installed

  [Regression Potential]
  Minimal, simply the service is now started earlier in the boot, as part of the multi-user.targer, rather than awaiting for dbus activation from command line tool or the nss-resolved module.

  [Testcase]
  Debootstrap minimal zesty, without libnss-resolve package installed, boot and check that 127.0.0.53 is present in /etc/resolv.conf and that systemd-resolved.service is running

  Context: fresh install of zesty via

  debootstrap --include=nano,dbus,iputils-ping,iproute2 zesty zesty1
  http://fr.archive.ubuntu.com/ubuntu

  ran via asystemd-nspawn with a static IP

  1. Upon first connexion, a ping fails:

  root at zesty1:~# ping google.com
  ping: google.com: Temporary failure in name resolution

  2. The content of /etc/resolv.conf:

  root at zesty1:~# cat /etc/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.

  3. When running systemd-resolve --status:

  root at zesty1:~# systemd-resolve --status
  Global
           DNS Servers: 8.8.8.8
                        8.8.4.4
                        2001:4860:4860::8888
                        2001:4860:4860::8844
            DNSSEC NTA: 10.in-addr.arpa
                        16.172.in-addr.arpa
                        168.192.in-addr.arpa
  (...)

  4. After running this command the resolution is miraculously restored:

  root at zesty1:~# ping google.com
  PING google.com (172.217.22.142) 56(84) bytes of data.
  64 bytes from 172.217.22.142 (172.217.22.142): icmp_seq=1 ttl=53 time=2.62 ms
  64 bytes from 172.217.22.142 (172.217.22.142): icmp_seq=2 ttl=53 time=1.93 ms

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