[Bug 1991658] [NEW] 22.04 upgrade left DNS broken, resolv.conf pointing at resolvconf

[Smylers]

Public bug reported:

I upgraded a server from Ubuntu 20.04.x to 22.04.1. It had originally
been installed as 16.04, and upgraded through all the LTS releases.

Immediately after upgrade, DNS resolving wasn't working; no names could
be resolved.

• /etc/resolv.conf was pointing to /run/resolvconf/resolv.conf
• That file said not to edit it by hand, gave 127.0.0.53 as the only name-server, and to run systemd-resolve --status to see details about the actual name-servers.
• Running systemd-resolve said the command wasn't found.
• man resolvconf gave the manual page for resolvectl, which said it had supplanted resolvconf and was only partially backwards compatible, when running systemd-resolved.service.
• systemd-resolved didn't appear to be running. systemctl status systemd-networkd said it was dead.

To get DNS working, I initially edited /etc/resolv.conf by hand to put
our name-server's IP address in there.

I then created a netplan config (this server predates netplan, and no
previous upgrades had switched anything to use it) in
/etc/netplan/eth0.yaml with the IP address and name-server config.
netplan apply started a name-server on 127.0.0.53. /etc/resolv.conf was
untouched; I removed the IP address I'd manually added and names
continued to resolve.

But that left /etc/resolv.conf still with the outdated message about
systemd-resolve --status in it. I found /run/systemd/resolve/stub-
resolv.conf so switched /etc/resolv.conf to symlink to that; it now has
a comment to use resolvectl status, a command which actually exists.

1.  It would have been preferable if upgrading Ubuntu LTS–LTS didn't
break networking such that names no longer resolved.

2.  If that breakage was inevitable from the set-up this server had, it
would have been much better if the upgrader had detected that and
declined to proceed with the upgrade — for instance by saying to switch
to netplan and systemd-networkd first.

3.  If the upgrade disables resolvconf, then the /etc/resolv.conf
symlink should be switched to point to whatever its modern equivalent
is.

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1991658

Title:
  22.04 upgrade left DNS broken, resolv.conf pointing at resolvconf

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  I upgraded a server from Ubuntu 20.04.x to 22.04.1. It had originally
  been installed as 16.04, and upgraded through all the LTS releases.

  Immediately after upgrade, DNS resolving wasn't working; no names
  could be resolved.

  • /etc/resolv.conf was pointing to /run/resolvconf/resolv.conf
  • That file said not to edit it by hand, gave 127.0.0.53 as the only name-server, and to run systemd-resolve --status to see details about the actual name-servers.
  • Running systemd-resolve said the command wasn't found.
  • man resolvconf gave the manual page for resolvectl, which said it had supplanted resolvconf and was only partially backwards compatible, when running systemd-resolved.service.
  • systemd-resolved didn't appear to be running. systemctl status systemd-networkd said it was dead.

  To get DNS working, I initially edited /etc/resolv.conf by hand to put
  our name-server's IP address in there.

  I then created a netplan config (this server predates netplan, and no
  previous upgrades had switched anything to use it) in
  /etc/netplan/eth0.yaml with the IP address and name-server config.
  netplan apply started a name-server on 127.0.0.53. /etc/resolv.conf
  was untouched; I removed the IP address I'd manually added and names
  continued to resolve.

  But that left /etc/resolv.conf still with the outdated message about
  systemd-resolve --status in it. I found /run/systemd/resolve/stub-
  resolv.conf so switched /etc/resolv.conf to symlink to that; it now
  has a comment to use resolvectl status, a command which actually
  exists.

  1.  It would have been preferable if upgrading Ubuntu LTS–LTS didn't
  break networking such that names no longer resolved.

  2.  If that breakage was inevitable from the set-up this server had,
  it would have been much better if the upgrader had detected that and
  declined to proceed with the upgrade — for instance by saying to
  switch to netplan and systemd-networkd first.

  3.  If the upgrade disables resolvconf, then the /etc/resolv.conf
  symlink should be switched to point to whatever its modern equivalent
  is.

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